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june 2011 doc id 15699 rev 7 1/50 1 stm8t141 single-channel capacitive sensor for touch or proximity detection with shielded sensing electrode features touch or proximity detection (a few centimeters) built-in driven shield function: ? enhance proximity detection ? protect sensing electrode from noise interference ultra-low power modes suitable for battery applications (11 a in extreme low power mode) on-chip integrated voltage regulator environment compensation filter user programmable options include: ? four detection thresholds ? four output modes ? four low power modes ? reference freeze timeout minimal external components applications consumer electronics power-critical and battery applications ? wake-up on proximity home and office appliances ? find-in-the-dark (fitd) applications using proximity detection ? sanitary ware and white goods flameproof human interface devices for use in hazardous environments table 1. device summary feature stm8t141 operating supply voltage 2.0 v to 5.5 v supported interface single key state output operating temperature ?40 to +85 c packages 8-pin so 8-pin ufdfpn so8 ufdfpn8 (2 x 3 mm) (narrow) www.st.com
contents stm8t141 2/50 doc id 15699 rev 7 contents 1 description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2 block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3 pin descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4 stm8t proxsense technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 4.1 capacitive sensing overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 4.2 charge transfer acquisition principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 5 stm8t processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5.1 signal and reference calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5.2 determining touch/proximity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5.3 environment compensation filter (ecf) . . . . . . . . . . . . . . . . . . . . . . . . . . 13 5.3.1 ecf principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 5.3.2 reference freeze timeout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5.3.3 debounce filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 6 typical application diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 7 device operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 7.1 option byte description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 7.2 tout/pout output mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 7.2.1 active . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 7.2.2 toggle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 7.2.3 3-second latch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 7.2.4 30-second latch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 7.3 detection threshold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 7.4 power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 7.4.1 normal power mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 7.4.2 low power mode with zoom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 7.4.3 extreme low power mode with zoom . . . . . . . . . . . . . . . . . . . . . . . . . . 24 7.4.4 extreme low power mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 7.5 charge transfer frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
stm8t141 contents doc id 15699 rev 7 3/50 7.6 sampling period . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 8 design guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 8.1 shield function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 8.1.1 shield application example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 8.2 sensitivity adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 8.2.1 c s influence on sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 8.2.2 pcb layout and construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 8.3 influence of power supply variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 9 electrical characteristi cs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 9.1 parameter conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 9.1.1 minimum and maximum values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 9.1.2 typical values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 9.1.3 typical curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 9.1.4 loading capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 9.2 absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 9.3 operating conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 9.3.1 general operating conditions and supply characteristics . . . . . . . . . . . 30 9.3.2 average current consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 9.3.3 output characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 9.4 regulator and reference voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 9.5 capacitive sensing characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 9.6 emc characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 9.6.1 functional ems (ele ctromagnetic susceptib ility) . . . . . . . . . . . . . . . . . . 35 9.6.2 prequalification trials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 9.6.3 electromagnetic interference (emi) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 9.6.4 absolute maximum ratings (electrical sensitivity) . . . . . . . . . . . . . . . . . 36 9.6.5 electrostatic discharge (esd) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 9.6.6 static latchup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 10 package characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 10.1 package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 10.1.1 so8 package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 10.1.2 ufdfpn8 package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 10.2 package thermal characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 10.2.1 reference document . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
contents stm8t141 4/50 doc id 15699 rev 7 11 ordering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 11.1 stm8t141 ordering information scheme . . . . . . . . . . . . . . . . . . . . . . . . . 42 11.2 orderable favorite device lists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 11.3 in-factory option byte programming service . . . . . . . . . . . . . . . . . . . . . . . 43 12 stm8t141 development tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 13 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
stm8t141 list of tables doc id 15699 rev 7 5/50 list of tables table 1. device summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 table 2. stm8t141 pin descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 table 3. explanation of ecf example 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 table 4. explanation of ecf example 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 table 5. option bytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 table 6. option byte description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 table 7. detection thresholds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 table 8. low power period according to selected power mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 table 9. voltage characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 table 10. current characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 table 11. thermal characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 table 12. operating characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 table 13. average current consumption without shield . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 table 14. output pin characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 table 15. regulator and reference voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 table 16. general capacitive sensing characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 table 17. response times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 table 18. external sensing component characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 table 19. ems data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 table 20. emi data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 table 21. esd absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 table 22. electrical sensitivities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 table 23. 8-lead plastic small outline - package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 table 24. 8-lead ultra thin fine pitch dual flat - package mechanical data . . . . . . . . . . . . . . . . . . . . . 40 table 25. thermal characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 table 26. orderable favorite device lists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 table 27. ordering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 table 28. document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
list of figures stm8t141 6/50 doc id 15699 rev 7 list of figures figure 1. stm8t141 block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 figure 2. s08 pinout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 figure 3. ufdfpn8 pinout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 figure 4. coupling with hand increases the capacitance of the sensing electrode . . . . . . . . . . . . . . 10 figure 5. stm8t measuring circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 figure 6. conversion period examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 figure 7. environmental compensation filter (ecf) example 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 figure 8. environmental compensation filter (ecf) example 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 figure 9. reference freeze timeout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 figure 10. typical application shematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 figure 11. possible load configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 figure 12. active mode output operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 figure 13. toggle mode output operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 figure 14. 3-second latch mode output operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1 figure 15. 30-second latch mode output operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 figure 16. charge cycle timing diagram in normal power mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 figure 17. charge cycle timing diagram in low power mode with zoom . . . . . . . . . . . . . . . . . . . . . . 24 figure 18. charge cycle timing diagram in extreme low power mode with zoom . . . . . . . . . . . . . . . 24 figure 19. charge cycle timing diagram in extreme low power mode . . . . . . . . . . . . . . . . . . . . . . . 25 figure 20. connecting the shield (coaxial cable implementation) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 figure 21. pin loading conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 figure 22. i dd average current consumption vs r shield . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 figure 23. sigma variation across v dd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 figure 24. so8-lead plastic small outline - package outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 figure 25. ufdfpn8-lead ultra thin fine pitch dual flat package (mlp) package outline . . . . . . . . . . 40 figure 26. stm8t141 ordering information scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 figure 27. stm8t141-eval evaluation kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 figure 28. stm8t141 blank module box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 figure 29. stm8t141-eval programming tool. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
stm8t141 description doc id 15699 rev 7 7/50 1 description the stm8t141 is a proxsense? single-channel, fully integrated, charge-transfer, capacitive sensor that is designed to repl ace conventional electromechanical switches in cost-sensitive applications. the stm8t141 is offered in 8-pin packages and is ideally suited for 1-button applications. it can be configured either in touch or proximity sensing mode for wake-up or backlighting on actuation. the extremely low current consumption makes it an ideal solution for battery-powered applications. the device features an internal voltage regulator to enhance detection sensitivity and stability. the stm8t141 touchpad can sense through almost any dielectric and can thereby contain the electronics in a sealed environment. the stm8t141 also inco rporates the advantages of using a driven shie lding capability. this makes it possible to separate the sealed electronics from the sensing electrode. the shield feature enables the designer to protect part of the sensing element from unwanted environmental interference and enhances proxim ity detection when used with battery (dc) applications. note: proxsense? is a trademark of azoteq.
block diagram stm8t141 8/50 doc id 15699 rev 7 2 block diagram figure 1. stm8t141 block diagram rc oscillator the 500-khz rc oscillator is an internal fixed frequency osc illator used to supply the clock to the mcu system engine. power-on-reset (por) the por generates a reset signal depending on the power supply level and the clock pulses received from the rc oscillator. voltage regulator the voltage regulator has an internal compar ison and feedback circuit that ensures the v reg voltage is kept stable and constant. the regulator requires an external smoothing capacitor. mcu system engine the mcu system engine controls the capaciti ve sensing engine and processes touch and proximity detection signals. proxsense engine the proxsense engine circuitry employs a c harge-transfer method to detect changes in capacitance. 500 khz rc o s cill a tor c x v ss tout/pout v dd por v reg a i17207 volt a ge reg u l a tor mcu s y s tem engine c s s hldout s hldin proxsense engine
stm8t141 pin descriptions doc id 15699 rev 7 9/50 3 pin descriptions figure 2. s08 pinout figure 3. ufdfpn8 pinout table 2. stm8t141 pin descriptions pin no. pin type (1) 1. i: input pin, od: open drain, pp: output push-pull pi n, s: supply pin and sns: capacitive sensing pin. pin name pin function so8 ufdfpn8 1sv ss ground 2snsc s capacitive sensing channel pin to c s (2) 2. use cog or npo capacitor type. 3snsc x capacitive sensing channel pin to r x 4ishldin (3) 3. if the active shield is unused, please connect this pin to v ss . shield input 5sv reg internal voltage regulator output (4) 4. requires a low esr, 1f capacitor to ground. this output must not be used to power other devices. 6 od shldout shield output 7sv dd supply voltage 8pptout/pout touch/proximity (5) output ? (active high) 5. depending on the value of bits [1:0] of opt0. !) 6 2%' 3(,$). 3(,$/54 6 $$ # 3 6 33 4/540/54 # 8 !) 6 2%' 3(,$). 3(,$/54 6 $$ # 3 6 33 4/540/54 # 8
stm8t proxsense technology stm8t141 10/50 doc id 15699 rev 7 4 stm8t proxsense technology 4.1 capacitive sensing overview a capacitance exists between any reference point and ground as long as they are electrically isolated. if this reference point is a s ensing electrode, it can help to think of it as a capacitor. the positive electrode of the capacitor is the sensing electrode, and the negative electrode is formed by the surrounding area (virtual ground reference in figure 4 ). figure 4. coupling with hand increases the capacitance of the sensing electrode when a conductive object is brought into proximity of the sensing electrode, coupling appears between them, and the capacitance of the sensing electrode relative to ground increases. for example, a human hand raises the capacitance of the sensing electrode as it approaches it. touching the dielectric panel that protects the electrode increases its capacitance significantly. 4.2 charge transfer acquisition principle to measure changes in the elec trode capacitance, stm8t devices employ bursts of charge- transfer cycles. the measuring circuitry is connected to the c x pin. it is composed of a serial resistor r x plus the sensing electrode itself of equivalent capacitance c x (see figure 5 ). the sensing electrode can be made of any electrically condu ctive material, such as copper on pcbs, or transparent conductive material like indium tin oxide (ito) deposited on glass or plexiglas. the dielectric panel usually provides a high degree of isolation to prevent esd discharge from reaching the stm8t touch sensing controller. connecting the serial resistor (r x ) to the c x pin improves esd immunity even more. c t lower capacitance c x higher capacitance sensing electrode
stm8t141 stm8t proxsense technology doc id 15699 rev 7 11/50 figure 5. stm8t measuring circuitry 1. r x must be placed as close as possible to the stm8t device. the principle of charge transfer is to charge the electrode capacitance (c x ) using a stable power supply. when c x is fully charged, part of the accumulated charge is transferred from c x to an external sampling capacitance, referred to as c s . the transfer cycle is repeated until the voltage across the sampling capacitor c s reaches the end of acquisition reference voltage (v trip ). the change in the electrode capacitance is detected by measuring the number of transfer cycles composing a burst (see figure 6 ). throughout this document the following naming conventions apply: the charge transfer period ( t transfer ) refers to the charging of c x and the subsequent transfer of the charge to c s . the burst cycle duration (t burst ) is the time required to charge c s to v trip . the sampling period (t sampling ) is the acquisition rate. figure 6. conversion period examples ai15249 a c x c x (~20 pf) c t (~5 pf) e a rth s eri a l re s i s tor (r x ) (1) s tm 8 t141 c s c s ( a few nf) ms t t 3!-0,).' # 3 !i t " 5234 6 2%' 6 42)0 t 42!.3&%2
stm8t processing stm8t141 12/50 doc id 15699 rev 7 5 stm8t processing the stm8t141 device is designed to ensure reliable operation whatever the environment and operating conditions. to achieve this high level of robustness, dedicated processing have been implemented: signal and reference calculation determining touch/proximity self-calibration environmental compensation filter debounce filter 5.1 signal and reference calculation capacitive touch or proximity sensing is a technique based on detecting the electrode capacitance change when someone is in proximity of the sensing electrode. the capacitance change, induced by the presence of a finger or a hand in the device detection area, is sensed by the variation in the number of charge transfer pulses composing the burst. the charge transfer pulse number, also called ?signal? is compared to a reference to decide if there is a touch/proximity detection or not. at power-up, a calibration sequence is performed to compute one reference value per capacitive sensing channel. the reference is extracted from 32 burst measurements. then, the ecf takes care of its slow evolution over time. to speed up the calibration process, the device is kept in normal mode whatever the low power mode selected. the device operates in the selected low power mode when the calibration process is completed. 5.2 determining touch/proximity the minimum difference between the reference and the signal necessary to report a touch/proximity is the detection threshold (d th ). a time filtering, similar to the debouncing of the mechanical switches, is applie d to avoid noise induced detections. four different detection threshold settings are available and selectable by option byte. the touch and sensitive touch levels are relative, which means the actual sensing distance is not influenced by the cs capacitor. the two thresholds should be able to adapt to various surroundings and panel material or thickness. the proximity sensitivity thresholds are absolute. this implies that the detection distance increases with the cs capacitor. it provides an easy way to tune the proximity sensing distance according to the application needs.
stm8t141 stm8t processing doc id 15699 rev 7 13/50 5.3 environment compensation filter (ecf) 5.3.1 ecf principle the capacitive sensing channel reference va lue increases or decreases according to environmental conditions such as temperature, power supply, moisture, and surrounding conductive objects. the stm8t141 includes a built-in digital infinite impulse response (iir) filter capable of tracking slow changes in the environment called the environment compensation filter (ecf). this is a first order digital low pass filter with a gain of one. the filter makes the reference follow slow changes of the signal while fast changes are recognized as a touch or proximity. when a touch or proximity condition is detected, the corresponding capacitive sensing channel reference is frozen. figure 7. environmental compensation filter (ecf) example 1 :one :one :one :one :one 2eference 2eference $ 4h 3ignal .umberofcounts $etection ai t table 3. explanation of ecf example 1 zone 1 zone 2 zone 3 zone 4 event description the object (finger) is outside the electrode field range. electrode environment is stable the object, is inside the electrode field range. it induces a signal change but, not large enough to cross the detection threshold (dth). the reference adapts slowly to the object proximity. the object comes inside the detection range before the reference compensates for its presence. a touch or proximity event is triggered because the signal level falls below the reference - d th . the object exits from the electrode?s detection range. detection state no detection detection no detection ecf operation active halt active reference adapting frozen adapting
stm8t processing stm8t141 14/50 doc id 15699 rev 7 figure 8. environmental compensation filter (ecf) example 2 detection reference - d th environment ch a nging n u m b er of co u nt s reference s ign a l zone 1 zone 2 zone 3 zone 4 a i17429 t table 4. explanation of ecf example 2 zone 1 zone 2 zone 3 zone 4 event description the system environment changes and the device adapts its reference according to this environment change. an object (finger) is detected. the environment continues to change. the object is still under detection but, the environment is not changing anymore. the object exits from detection. detection operation no detection detection no detection ecf state active halt active reference adapting frozen adapting surrounding environment changing stable
stm8t141 stm8t processing doc id 15699 rev 7 15/50 5.3.2 reference freeze timeout to prevent an object under detection from influencing the reference value, the ecf is halted as soon as a detection happens. consequently, the reference is frozen. in order to be able to recover from a sudden environment change, the reference freeze ends after a maximum programmable delay called the ?reference freeze timeout? (t rft ). when a detection lasts longer than the t rft , the ecf is enabled again and the reference moves toward the detection signal. after a short period of time, the difference between the signal and the reference become smaller than the detection threshold and the device reports no detection. note: reference freeze timeout was incorrectly called ?recalibration timeout? in previous versions of this document. figure 9. reference freeze timeout 1. see max values of t rft in table 16: general capacitiv e sensing char acteristics . 2. between the moment when the finger is removed from the s ensor and the instant the reference - d th curve crosses the signal limit, the device is unable to detect a new touch. th is delay is called ? masked detection window? . it depends on the environmental change or object signal variatio n speed inside the electrode?s field. the detection threshold also impac ts the masked detection window. 2eference 2eference $ 4h 3ignal t .umberofcounts .odetection $etection .odetection .odetection %#&active %#&active %#&frozen ai %#&freeze timeout -askeddetection window 3ignallimit t 2&4
stm8t processing stm8t141 16/50 doc id 15699 rev 7 5.3.3 debounce filter the debounce filter mechanism works together with the ecf to dramatically reduce the effects of noise on the touch and proximity detection. debouncing is applied to acquisition samples to filter undesired abrupt changes. the number of consecutive detection debounce count (ddc) and end of detection debounce count (eddc) needed to identify a proximity/touch detection are defined in section 9.5: capacitive sensing characteristics on page 33 .
stm8t141 typical application diagram doc id 15699 rev 7 17/50 6 typical application diagram figure 10. typical application shematic 1. if the active shield is not used, the shldin pin must be grounded, shldout should be left unconnected, and r shield can be removed. 2. use cog or npo or higher grade capacitor. the smaller the value of the r shield resistor, the better its effect but, the greater the device consumption. pin tout/pout can directly drive a hv fet (as shown in figure 11 ) that, in turn, can drive any load. figure 11. possible load configurations a touch or proximity detection is defined as an actuation (high = logical '1' and ? low = logical '0'). ai n& 3ensingelectrode '.$ 3hield '.$ 2 8 '.$ '.$ 6 33 # 3 # 8 3(,$). 4/540/54 4/540/54 6 $$ 2 3()%,$ '.$ ?& n& ?& 6 2%' 3(,$/54 6 $$ gnd a led l ed as l o a d b c 3 d 1g 2 s r rel a y on lo a d termin a l s to s witch a ny high volt a ge lo a d low volt a ge dc light b u l b as lo a d 3 4 1 2 5 k1 tout/pout lo a d volt a ge lo a d po s lo a d neg lo a d po s lo a d neg lo a d neg lo a d po s lo a d po s lo a d neg a i1552 3
device operation stm8t141 18/50 doc id 15699 rev 7 7 device operation the stm8t141 can be configured through a set of selectable one-time programmable (otp) option bytes. these options can be used in their default (unconfigured) state or set for specific applications. for large orders, preconfigured devices are available (please refer to section 11: ordering information ). the stm8t141 can be configured to act as a touch or proximity detection device. a number of other options are also user programmable, including: four output modes ?active mode ? toggle mode ? 3-second latch mode ? 30-second latch mode tout/pout output mode selection four detection thresholds ? two for touch detection ? two for proximity detection four power modes ? normal power mode ? three low power modes reference freeze timeout 7.1 option byte description a set of tools is supplied by stmicroelectronics to program the user otp options for prototyping purposes. please refer to section 12: stm8t141 development tools for more details. note: devices that are not yet programmed (?blank? devices) are delivered cleared (at value ?0?) for all bits. the user options allow the stm8t141 to be customized for each specific application. default values for the oscillator, conversion rate (t sampling ), filter freeze and device reset settings should be used initially for first designs. table 5. option bytes option byte no. option bits factory default setting bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 opt1 reserved sampling period charge transfer frequency reserved 0xx0 opt0 power mode dete ction threshold reference freeze timeout tout/pout output mode 0x00
stm8t141 device operation doc id 15699 rev 7 19/50 table 6. option byte description option byte no. description opt1 bits [7:3] : reserved bit 2 : sampling period (t sampling ) ( section 7.6: sampling period ) 0: conversion period is 20 ms ? 1: conversion period is 10 ms bit 1 : charge transfer frequency (f transfer ) ( section 7.5: charge transfer frequency ) 0: 125 khz ? 1: 250 khz bit 0 : reserved opt0 bits [7:6] : power mode ( section 7.4: power modes ) 00: low power mode with zoom ? 01: normal power mode ? 10: extreme low power mode with zoom ? 11: extreme low power mode bits [5:4] : detection threshold ( section 7.3: dete ction threshold ) 00: standard proximity ? 01: standard touch ? 10: sensitive proximity ? 11: sensitive touch bits [3:2] : reference freeze timeout ( section 5.3.2: reference freeze timeout ) 00: 15-second reference freeze timeout ? 01: 45-second reference freeze timeout ? 10: reserved ? 11: infinite reference freeze bits [1:0] : tout/pout output mode ( section 7.2: tout/pout output mode ) 00: active mode ? 01: toggle mode ? 10: 3-second latch mode ? 11: 30-second latch mode
device operation stm8t141 20/50 doc id 15699 rev 7 7.2 tout/pout output mode four output modes are available on the stm8t141: active mode toggle mode 3-second latch mode 30-second latch mode for each output operation described, touch or proximity detection can be used. upon the detection of either of thes e actions, the tout/pout pin will latch high, otherwise the tout/pout pin stays low. the detailed working of each user interface is described below. the tout/pout pin is active high, and can sour ce enough current to directly drive a led. the pin is sourced from v dd when active. the tout/pout pin always goes high for a minimum time of t high . for more information, please refer to section 9: electrical characteristics . bits [1:0] of option byte opt0 are used to select the correct output mode. 7.2.1 active upon the detection of an act uation, the condition of the to ut/pout pin will change to high and stay high for as long as the touch or proximity detection condition occurs. figure 12 illustrates this output operation. figure 12. active mode output operation 4ouchproximitydetection 4/540/54 $etection .odetection (igh ,ow t t ?
stm8t141 device operation doc id 15699 rev 7 21/50 7.2.2 toggle upon the detection of an act uation, the tout/pout pin will toggle between high and low. thus if tout/pout is low, an actuation will c hange it to hi gh, and also if tout/pout is high, an actuation will change it to low. figure 13 illustrates this output operation. figure 13. toggle mode output operation 7.2.3 3-second latch upon the detection of an actuation the tout/pout pin will latch high for 3 seconds minimum. if the actuation occurs for longer than 3 seconds, the tout/pout pin will stay high and will only go low when the actuation stops. figure 14. 3-second latch mode output operation 4/540/54 $etection .odetection (igh ,ow 4ouchproximitydetection ? t t 4imethattouchorproximity detectionisstillactive sec sec sec 4/540/54 ? $etection .odetection (igh ,ow 4ouchproximitydetection t t
device operation stm8t141 22/50 doc id 15699 rev 7 7.2.4 30-second latch upon the detection of an act uation, the tout/pout pin will latch high. after 30 seconds from when the actuation stops, the tout/pout pin will go low. if the tout/pout pin is high and another actuation occur before the 30 seconds has expired, the counter will reset an d only 30 seconds after the ne w actuation has stopped, will the tout/pout pin go low. figure 15 illustrates this output operation. figure 15. 30-second latch mode output operation 7.3 detection threshold the user has a choice between four detection threshold levels (d th ) at which the touch or proximity detection condition is triggered. this depends on which threshold configuration is selected. see ta bl e 7 for more details regarding the detection threshold selections. bits [5:4] of option byte opt0 are used to select the correct detection threshold levels. 4/540/54 4ouchproximitydetection sec ? sec sec $etection .odetection (igh ,ow t t table 7. detection thresholds sensitivity d th setting description most sensitive least sensitive sensitive proximity threshold proximity for battery-powered applications. standard proximity threshold proximity with good ground. contact through ? 3 mm acrylic glass and no ground. sensitive touch threshold contact through thin acrylic glass with battery application. standard touch threshold contact through thin dielectric with good ground.
stm8t141 device operation doc id 15699 rev 7 23/50 7.4 power modes the stm8t141 device offers four power modes. the low power modes are specifically designed for battery applications: normal power mode low power mode with zoom extreme low power mode with zoom extreme low power mode burst cycles can occur either every 10 ms or 20 ms according to the selected sampling period (t sampling ). by selecting low power modes, extra delays are interlaced between bursts. this improves the device current consumption at the expense of the response time. bits [7:6] of option byte opt0 are used to select the correct power mode. 7.4.1 normal power mode when in normal power mode, burst cycles occur at the rate of t sampling . no extra delays are added between burst cycles ( figure 16 ). figure 16. charge cycle timing diagram in normal power mode table 8. low power period according to selected power mode power mode condition t lp value normal power mode 0 low power mode with zoom touch or proximity detection 0 untouched 4 x t sampling extreme low power mode with zoom touch or proximity detection 0 untouched 16 x t sampling extreme low power mode 16 x t sampling 1234567891011121314151617181920 c s burst cycle duration t
device operation stm8t141 24/50 doc id 15699 rev 7 7.4.2 low power mode with zoom with the stm8t141 in low power mode wi th zoom, burst cycles occur every 5th t sampling period (or 20% of the normal power mode). once activity is detected, the stm8t141 device wakes up from low power mode with zoom to normal power mode with ch arge cycles occurring every t sampling period. the device will return to low power mode after an end of low power period (t elp ) when no touch or proximity detection conditions are detected. this enables the device to reduce power consumption when not in use, and still have a sufficient response time when needed ( figure 17 ). figure 17. charge cycle timing diagram in low power mode with zoom 7.4.3 extreme low power mode with zoom with the stm8t141 in extreme low power mode with zoom, burst cycles only occur every 17th t sampling period (or 5.88% of the normal power mode). once activity is detected, the stm8t141 device wakes up from extreme low power mode and zoom to normal power mode with charge cycles occurring every t sampling . the device will return to low power mode after an end of low power period (t elp ) when no touch or proximity detection conditions are detected. this enables the device to reduce power consumption when not in use and still have a sufficient respon se time when needed ( figure 18 ). figure 18. charge cycle timing diagram in extreme low power mode with zoom 1234567891011121314151617181920 c s t zoom to normal mode after touch or proximity detection occurred burst cycle duration t lp 1234567891011121314151617181920 c s burst cycle every 17th t sampling period t zoom to normal mode after touch or proximity detection occurred t lp
stm8t141 device operation doc id 15699 rev 7 25/50 7.4.4 extreme low power mode with the stm8t141 in extreme low power mode, burst cycles only occur every 17th t sampling period (or 5.88% of the normal power mode), thus adding 16 extra delays of t sampling between charge cycles to conserve power. this reduces the amount of burst cycles in extreme low power mode even more than low power mode which in turn saves even more power but comes at the expense of a higher system response time ( figure 19 ). figure 19. charge cycle timing diagram in extreme low power mode 7.5 charge transfer frequency the stm8t141 offers two charge transfer frequencies. the charge transfer frequency must be adjusted depending on the c s capacitor. the charge transfer frequency may need to be raised to 250 khz in order to reduce t burst when the c s capacitance is large. 125 khz 250 khz bit 1 of option byte opt1 is used to select the correct charge transfer frequency. 7.6 sampling period the default sampling period (t sampling ) is configurable in order to allow different compromises between power consumption and conversion rates: 20-ms sampling rate to reduce average power consumption 10-ms sampling rate to increase detection response time when using a faster sampling rate (t sampling = 10 ms), all the timing values of the power modes will occur at twice the speed. bit 2 of option byte opt1 is used to select the correct conversion period. 1234567891011121314151617181920 c s burst cycle every 17th t sampling period t t lp
design guidelines stm8t141 26/50 doc id 15699 rev 7 8 design guidelines 8.1 shield function the stm8t141 offers a built-i n shielding function. this function provides the following advantages for designing the end-application: sensing electrode separated from sealed electronics. sensing wire shielded from unwanted environmental interferences. enhanced proximity detection when used with battery (dc) applications. the shield principle consists in actively driving the shield plane or element with the same signal as that of the electrode. the parasit ic capacitance between the electrode and the shield does not need to be charged anymore and its effect on the sensitivity is cancelled. note: grounding the shield reduces the sensitivity of the keys and may render the system unusable. 8.1.1 shield application example ideally, a coaxial cable is used for the shield. a r x (typically 2 k ? ) resistor should be connected to the c x pin. the other side of the r x resistor should be connected to the center core of the coaxial cable. the shldout pin shou ld be connected to th e metallic shield part of the coaxial cable. a pull-up resistor (r shield ) should be added between shldout and v dd as shown in figure 20 . the example shown in figure 20 is given for r x = 2 k ? , r shield = 100 k ? , and v dd = 5 v (a) . this setup has been successfully implemented with a coaxial cable of up to 4 m. a longer coaxial cable could be used, but this would mean decreasing the r shield resistor, and consequently increasing current consumption. note: a smaller r shield ensures better shielding but increases current consumption (see figure 20 ). a. v dd must range from 4.5 to 5.5 v to use the shield function.please refer to table 12: operating characteristics for the correct power supply operating vo ltage when using the shield function.
stm8t141 design guidelines doc id 15699 rev 7 27/50 figure 20. connecting the shield (coaxial cable implementation) 8.2 sensitivity adjustment several factors impact device sensitivity: the sensing electrode material and size the touch panel material and thickness the board layout and in particular the sensing signal tracks the value of the sampling capacitor (c s ) for proximity thresholds only the ground coupling of the object (finger or hand) and sensor. the touch or proximity detection threshold selected by the option byte. 8.2.1 c s influence on sensitivity in touch mode, the cs capacitor value has no in fluence on the sensitivity as the thresholds are relative to the actual reference value. in proximity mode, the cs value allows the sensivity to be tuned. a higher sampling capacitor value increases the resolution and the sensitivity but also the charging time. decreasing the sampling capacitor value therefore decreases the sensitivity. for more details, please refer to application note an2966 . 8.2.2 pcb layout and construction the pcb traces, wiring, and components associated or in contact with c x pins become touch sensitive and should be treated with caution to limit the touch area to the desired location. as an example, multiple touch electrodes connected to a sensing channel can be used to create control surfaces on both sides of an object. it is important to limit the amount of stray capacitance on the c x pin. this can be done by minimizing trace lengths and widths to achieve for higher gain without using higher values of c s . to minimize cross-coupling, electrode traces from adjacent sensing channel should not run close to each other for long distances. for detailed information on the impacts of the first three factors, refer to application note an2869. v dd s hldout c x pl as tic j a cket met a l s hield center core dielectric in su l a tor a i15527 100 k r s hield r x s hldin coaxial cable 2 k
design guidelines stm8t141 28/50 doc id 15699 rev 7 8.3 influence of power supply variation the stability of the device power supply is cr itical in order to provide a precise and repeatable capacitance measure. for this reason, a linear regulator is embedded into the device to provide the best power supply noise rejection possible. even with the embedded regulator, variations of the power supply voltage may have an impact on the measured signal, especially in proximity configurations with a large acquisition gain and small detection threshold. a variation of the power supply voltage ( ? v) induces a variation of the signal burst count ( ? bc) according to equation 1 . equation 1 the gain, g, of the acquisition is the ratio cs/cx. the parameter ? is the power supply rejection ratio. for stability reasons, it is advised to limit ? bc to less than half the detection threshold. if v dd is less than 2.9 v, special care should be taken of the supply quality. an external voltage regulator may be necessary. ? bc g ? ?? v ? =
stm8t141 electrical characteristics doc id 15699 rev 7 29/50 9 electrical characteristics 9.1 parameter conditions unless otherwise specified, all voltages are in reference to v ss . 9.1.1 minimum and maximum values unless otherwise specified, the minimum and maximum values are guaranteed in the worst conditions of ambient temperature and supply voltage by tests in production on 100% of the devices with an ambient temperature at t a = 25 c and t a = t a max (given by the selected temperature range). data based on characterization results, desi gn simulation and/or technology characteristics are indicated in the table footnotes and are not tested in production. based on characterization, the minimum and maximum values refer to sample tests and represent the mean value plus or minus three times the standard deviation (mean 3 ? ). 9.1.2 typical values unless otherwise specified, typical data are based on t a = 25 c, and v dd = 5 v. they are given only as design guidelines and are not tested. 9.1.3 typical curves unless otherwise specified, all typical curves are given only as design guidelines and are not tested. 9.1.4 loading capacitor the loading conditions used for pin parameter measurement are shown in figure 21 . figure 21. pin loading conditions output pin 50 pf
electrical characteristics stm8t141 30/50 doc id 15699 rev 7 9.2 absolute maximum ratings stresses above those listed as ?absolute ma ximum ratings? may cause permanent damage to the device. this is a stress rating only and functional operation of the device under these conditions is not implied. exposure to maximum rating conditions for extended periods may affect device reliability. 9.3 operating conditions 9.3.1 general operating conditions and supply characteristics table 9. voltage characteristics symbol ratings maximum value unit v dd ? v ss supply voltage 5.5 v table 10. current characteristics symbol ratings maximum value unit i vdd total current into v dd power lines (source) (1) 1. all power (v dd ) and ground (v ss ) lines must always be connec ted to the external supply. 11 ma i vss total current out of v ss ground lines (sink) (1) 11 i io output current sunk by output pin 10 output current sourced by output pin 10 table 11. thermal characteristics symbol ratings value unit t stg storage temperature range ?? 65 to +150 c t j junction temperature range (so8 narrow and ufdfpn8 packages) 90 c table 12. operating characteristics symbol parameter condition min. max. unit v dd supply voltage shield feature not used ? shield feature used 2.0 4.5 5.5 5.5 v t a operating temperature - -40 85 c t vdd turn-on slope (rise time rate) 01 v/s turn-off slope (fall time rate) 1 (1) 1. this constraint must be respect ed only if the voltage does not reach 0 v. ?
stm8t141 electrical characteristics doc id 15699 rev 7 31/50 9.3.2 average current consumption test conditions: t a = 25 c, c x = 20 pf, c s = 47 nf and r x = 2 k ? .. note: consumption does not depend on either detection threshold or acquisition rate. figure 22. i dd average current consumption vs r shield 1. extlp = external low power mode 2. lp = low power mode 3. np = normal power mode table 13. average current consumption without shield symbol parameter conditions typ. max. unit i dd normal power mode ? shield output unconnected ? shield input grounded ? options other than low power are left in default configuration 30 45 (1) 1. data based on characterization results, not tested in production. a low power 17 extreme low power mode 11 2 3()%,$ k/hms %xt,0 ,0 .0 ai ) $$ ?!
electrical characteristics stm8t141 32/50 doc id 15699 rev 7 9.3.3 output characteristics 9.4 regulator and reference voltage table 14. output pin characteristics symbol parameter conditions typ. max. unit v ol v dd = 5 v i load = 8 ma 1200 1600 mv i load = 4 ma 540 750 i load = 2 ma 250 450 v dd = 3.3 v i load = 4 ma 650 1000 i load = 2 ma 320 500 v dd = 2.9 v i load = 2 ma 400 500 v dd = 2.0 v i load = 1 ma 300 500 v oh v dd = 5 v i load = ?2 ma 4.7 v i load = ?4 ma 4.4 i load = ?8 ma 3.9 v dd = 3.3 v i load = ?2 ma 3.0 i load = ?4 ma 2.7 v dd = 2.9 v i load = ?2 ma 2.5 v dd = 2.0 v i load = -100 a 1.8 t high output minimum high time 40 ms t low output minimum low time 40 table 15. regulator and reference voltage symbol parameter min. typ. max. unit c ref voltage regulator decoupling capacitance (1) 1. equivalent serial r resistor ? 0.2 ? at 1 mhz. 110f v reg regulated voltage during acquisition 2.1 v v trip end of acquisition reference voltage 0.68
stm8t141 electrical characteristics doc id 15699 rev 7 33/50 9.5 capacitive sensing characteristics . table 16. general capacitive sensing characteristics (1) 1. values guaranteed by design. symbol parameter min. typ. max. unit f transfer charge-transfer frequency at 125-khz setting 90 125 160 khz charge-transfer frequency at 250-khz setting 185 250 315 t sampling scanning period at 10-ms setting 7.5 10 12.5 ms scanning period at 20-ms setting 15 20 25 t lp low power 4 t sampling extreme low power 16 t sampling t elp time before switching back to low power mode 540 t rft (2) 2. see t rft in figure 9: reference freeze timeout . 15 s reference freeze timeout 11 15 19 s 45 s reference freeze timeout 33 45 57 t burst burst detection 32 2 14 t transfer ddc detection debounce count 4 counts eddc end of detection debounce count 3 d th (3) 3. reference value (ref.) described in section 5.3.3: debounce filter on page 16 . proximity detection threshold ? 8 counts sensitive proximity detection threshold ? 2 touch detection threshold ref./16 sensitive touch detection threshold ref./32 ? (4) 4. between 3 v and 3.5 v, ? ? evolves as shown in figure 23 . power supply rejection ratio v ddmin < v dd < 3 v) 0.0250 count/v power supply rejection ratio (3.5 v < v dd < v ddmax ) 0.0005
electrical characteristics stm8t141 34/50 doc id 15699 rev 7 figure 23. sigma variation across v dd table 17. response times (1) 1. values guaranteed by design. mode t sampling = 10 ms t sampling = 20 ms unit min. max. min. max. normal power mode 30 50 60 100 ms low power with zoom mode 30 100 60 200 extreme low power with zoom mode 30 250 60 500 extreme low power mode 510 850 1020 1700 table 18. external sensing component characteristics symbol parameter min. typ. max. unit c s sampling capacitor (cog or npo type) (1) 1. for more information about capacitors, please refer to application note: an2966. 47 2 14 x c x nf c x equivalent electrode capacitance 100 pf c t equivalent touch capacitance 5 r x electrode serial resistance 2 22 kohm r shield shield pull-up resistance 1 1000 3igma"#6 6 $$ 6 ai
stm8t141 electrical characteristics doc id 15699 rev 7 35/50 9.6 emc characteristics susceptibility and em ission tests are performed on a sample basis during product characterization. both the sample and its applicative hardware environment ( figure 10 ) are mounted on a dedicated specific emc board defined in the iec61967-1 standard. 9.6.1 functional ems (elect romagnetic susceptibility) while running in the above described environment the product is stressed by two electromagnetic events until a failure occurs. esd : electrostatic discharge (positive and negati ve) is applied on all pins of the device until a functional disturbance occurs. this test complies with the iec 1000-4-2 standard. ftb : a burst of fast transient voltage (positive and negative) is applied to v dd and v ss through a 100 pf capacitor, until a functional disturbance occurs. this test complies with the iec 1000-4-4 standard. a device reset allows normal operations to be resumed. the test results are given in ta bl e 19 based on the ems levels and classes defined in application note an1709. 9.6.2 prequalification trials table 19. ems data symbol parameter conditions level/class v fesd voltage limits to be applied on any pin to induce a functional disturbance v dd ?? 5 v, t a ? +25 c, so8 (narrow) package, complies with iec 1000-4-2 1b v eftb fast transient voltage burst limits to be applied through 100pf on v dd and v ss pins to induce a functional disturbance v dd ?? 5 v, t a ? +25 c, so8 (narrow) package, complies with iec 1000-4-4 4a
electrical characteristics stm8t141 36/50 doc id 15699 rev 7 9.6.3 electromagnetic interference (emi) emission tests conform to the iec61967-2 standard for board layout and pin loading. worse case emi measurements are performed during maximum device activity. 9.6.4 absolute maximum rati ngs (electrical sensitivity) based on two different tests (esd and lu) using specific measurement methods, the product is stressed in order to determine its per formance in terms of electrical sensitivity. for more details, refer to the application note an1181. 9.6.5 electrostatic discharge (esd) electrostatic discharges (3 positive then 3 n egative pulses separated by 1 second) are applied to the pins of each sample according to each pin combination. the sample size depends on the number of supply pins in the device (3 parts*(n+1) supply pin). this test conforms to the jesd22-a114a/a115a standard. for more details, refer to the application note an1181. table 20. emi data symbol parameter general conditions monitored frequency band rc osc = 500 khz (1) 1. data based on characterization results, not tested in production. unit s emi peak level v dd ?? 5 v, t a ?? +25 c, ? so8 (narrow) package, ? complies with sae j1752/3, no finger on touch electrode 0.1 mhz to 30 mhz -4 dbv 30 mhz to 130 mhz -9 130 mhz to 1 ghz -6 sae emi level -1 peak level v dd ?? 5 v, t a ?? +25 c, ? so8 (narrow) package, ? complies with sae j1752/3, finger on touch electrode 0.1 mhz to 30 mhz 20 dbv 30 mhz to 130 mhz -8 130 mhz to 1 ghz -7 sae emi level 15 table 21. esd absolute maximum ratings symbol ratings conditions class maximum value (1) 1. data based on characterization results, not tested in production unit v esd(hbm) electrostatic discharge voltage ? (human body model) t a ?? +25c, conforming to jesd22-a114 a2000v v esd(cdm) electrostatic discharge voltage ? (charge device model) t a ?? +25c, conforming to jesd22-c101 iv 1000 v
stm8t141 electrical characteristics doc id 15699 rev 7 37/50 9.6.6 static latchup two complementary static tests are required on 10 parts to assess the latchup performance. a supply overvoltage (applied to each power supply pin) and a current injection (applied to each input, output and configurable i/o pin) are performed on each sample. this test conforms to the eia/jesd 78 ic latchup standard. for more details, refer to application note an1181. table 22. electrical sensitivities symbol parameter conditions class (1) 1. class description: a class is an stmi croelectronics internal specification. all its limits are higher than the jedec specifications, that means when a device belongs to class a it exceeds the jedec standard. b class strictly covers all the jedec criteria (international standard). lu static latchup class t a ?? +25 c a t a ?? +85 c a
package characteristics stm8t141 38/50 doc id 15699 rev 7 10 package characteristics in order to meet environmental requirements, st offers these devices in different grades of ecopack? packages, depending on their level of environmental compliance. ecopack? specifications, grade definitions and product status are available at www.st.com . ecopack? is an st trademark. 10.1 package mechanical data 10.1.1 so8 package mechanical data figure 24. so8-lead plastic small outline - package outline so-a e1 8 ccc b e a d c 1 e h x 45? a2 k 0.25 mm l l1 a1 gauge plane
stm8t141 package characteristics doc id 15699 rev 7 39/50 table 23. 8-lead plastic small outline - package mechanical data symbol millimeters inches (1) 1. values in inches are rounded to 4 decimal digits min. typ. max. min. typ. max. a - - 1.750 - - 0.0689 a1 0.100 - 0.250 0.0039 - 0.0098 a2 1.250 - - 0.0492 - - b 0.280 - 0.480 0.0110 - 0.0189 c 0.170 - 0.230 0.0067 - 0.0091 ccc - - 0.100 - - 0.0039 d (2) 2. dimension d does not include mold flas h, protrusions or gate burrs. mold flash, protrusions or gate burrs shall not exceed 0.15mm in total (both side). 4.800 4.900 5.000 0.1890 0.1929 0.1969 e 5.800 6.000 6.200 0.2283 0.2362 0.2441 e1 (3) 3. dimension e1 does not include interlead flash or pr otrusions. interlead flash or protrusions shall not exceed 0.25 mm per side. 3.800 3.900 4.000 0.1496 0.1535 0.1575 e - 1.270 - - 0.0500 - h 0.250 - 0.500 0.0098 - 0.0197 k 0 - 8 0 - 8 l 0.400 - 1.270 0.0157 - 0.0500 l1 - 1.040 - - 0.0409 -
package characteristics stm8t141 40/50 doc id 15699 rev 7 10.1.2 ufdfpn8 package mechanical data figure 25. ufdfpn8-lead ultra thin fine pitch dual flat package (mlp) package outline table 24. 8-lead ultra thin fine pitch dual flat - package mechanical data symbol millimeters inches (1) 1. values in inches are rounded to 4 decimal digits min typ max min typ max a 0.450 0.550 0.600 0.0177 0.0217 0.0236 a1 0.000 0.020 0.050 0.0000 0.0008 0.0020 b 0.200 0.250 0.300 0.0079 0.0098 0.0118 d 1.900 2.000 2.100 0.0748 0.0787 0.0827 d2 1.500 1.600 1.700 0.0591 0.0630 0.0669 e 2.900 3.000 3.100 0.1142 0.1181 0.1220 e2 0.100 0.200 0.300 0.0039 0.0079 0.0118 e - 0.500 - - 0.0197 - l 0.400 0.450 0.500 0.0157 0.0177 0.0197 l1 - - 0.150 - - 0.0059 l3 0.300 - - 0.0118 - - tolerance millimeters inches ddd (2) 2. applied for exposed die paddle and terminals. exclude embedding part of exposed die paddle from measuring. - 0.080 - - 0.0031 - d e ufdfpn-01 a a1 ddd l1 e b d2 l e2 l3
stm8t141 package characteristics doc id 15699 rev 7 41/50 10.2 package thermal characteristics the maximum chip junction temperature (t jmax ) must never exceed the values given in ta bl e 12: operating characteristics on page 30 . the maximum chip-junction temperature, t jmax , in degrees celsius, may be calculated using the following equation: t jmax = t amax + (p dmax x ? ja ) where: t amax is the maximum ambient temperature in ? c ? ja is the package junction-to-ambient thermal resistance in ?? c/w p dmax is the sum of p intmax and p i/omax (p dmax = p intmax + p i/omax ) p intmax is the product of i dd and v dd , expressed in watts. this is the maximum chip internal power. p i/omax represents the maximum power dissipation on output pins ? where: ? p i/omax = ?? (v ol *i ol ) + ? ((v dd -v oh )*i oh ), ? taking into account the actual v ol /i ol and v oh /i oh of the i/os at low and high level in the application. 10.2.1 reference document jesd51-2 integrated circuits thermal test method environment conditions - natural convection (still air). available from www.jedec.org. table 25. thermal characteristics (1) 1. thermal resistances are based on jedec jesd51- 2 with 4-layer pcb in a natural convection environment. symbol parameter value unit ? ja thermal resistance junction-ambient ? so8 (narrow) 130 c/w ? ja thermal resistance junction-ambient ? ufdfpn 8 (2 x 3 mm) 120 c/w
ordering information stm8t141 42/50 doc id 15699 rev 7 11 ordering information 11.1 stm8t141 orderi ng information scheme figure 26. stm8t141 ordering information scheme 1. see table 26: orderable favorite device lists and the explanation below of ?in factory option byte programming service? 2. the stm8t141 otp devices are available for producti on and development. these parts are blank devices with unconfigured option bytes (all opti on bits are set to ?0?). for more ? information, please refer to section 7: device operation . stm8t 141 a m xxxy tr device type stm8t: st touch sensing mcu package m: s08 (small outline) u: fpn (dual flat no lead) packing no character: tray or tube tr: tape and reel example: pin count a: 8 pins device sub-family 141 = 1 channel/proximity device configuration xxxy: device with specific configuration (1) 61t: otp blank device (all user bits set to 0) (2)
stm8t141 ordering information doc id 15699 rev 7 43/50 11.2 orderable favorite device lists 11.3 in-factory option by te programming service for specific configur ations not listed in ta bl e 26: orderable favorite device lists , in-factory option byte programming is available on customer request and for large order quantities. customers have to fill out the option list (see below) and send it back to stmicroelectronics. customers are then informed by stmicroelectronics about the ordering part number corresponding to the customer configuration. the x xxy parameter of the final ordering part number (e.g. stm8t141amxxxy) depends on the de vice configuration a nd is assigned by stmicroelectronics. table 26. orderable favorite device lists config. option byte configuration (1) part numbers sampling period charge transfer frequency power modes detection threshold reference freeze timeout tout/ pout output mode so8 ufdfpn8 default config. (otp) 20 ms 125 khz low power mode with zoom standard proximity 15 s active mode stm8t141am61t STM8T141AU61Ttr 20 ms 125 khz low power mode with zoom sensitive touch infinite active mode not yet available stm8t141au maj1 tr (xxxy = maj1) 1. please refer to section 7: device operation .
ordering information stm8t141 44/50 doc id 15699 rev 7 1. configuration by default in otp devices. s tm 8 t141 pro g rammin g s ervice option li s t (la s t update: february 2010) cu s tomer name: addre ss : contact name: phone number: select the package type (tick one box) stm8t141am6 - s08 or stm8t141au6 ? dfn8 cu s tomer s ettin gs (tick one box by option) sa mpling period ( s ee s ection 7.6: sa mpling period ) 10 m s sa mpling period 20 m s sa mpling period (1) ch a rge tr a n s fer fre qu ency ( s ee s ection 7.5: ch a rge tr a n s fer fre qu ency) 125 khz (1) 250 khz power mode s ( s ee s ection 7.4: power mode s ) norm a l power mode low power mode with zoom (1) extreme low power mode with zoom extreme low power mode detection thre s hold ( s ee s ection 7. 3 : detection thre s hold ) s en s itive proximity s t a nd a rd proximity (1) s en s itive to u ch s t a nd a rd to u ch reference freeze timeo u t ( s ee s ection 5. 3 .2:reference freeze timeo u t ) 15- s econd reference freeze timeo u t (1) 45- s econd reference freeze timeo u t infinite reference freeze tout/pout o u tp u t mode ( s ee s ection 7.2: tout/pout o u tp u t mode ) active mode (1) toggle mode 3 - s econd l a tch mode 3 0- s econd l a tch mode p a ck a ging t a pe & reel t ub e comment : d a te s ign a t u re :
stm8t141 stm8t141 development tools doc id 15699 rev 7 45/50 12 stm8t141 development tools stm8t141 evaluation kit the stm8t141-eval is an evaluation kit whic h introduces developers to the stm8t141. it contains an stm8t141 evaluation board, plus a set of preconfigured plug-in modules which allow the stm8t141 device performances to be evaluated in either touch or proximity detection. figure 27. stm8t141-eval evaluation kit
stm8t141 development tools stm8t141 46/50 doc id 15699 rev 7 stm8t141 ?blank? modules an additional box of 10 stm8t141 ?blank? modules (stm8t141am-mod) can be ordered separately, where the device option bytes are left unprogrammed (see figure 28 ). figure 28. stm8t141 blank module box 1. the above figure is not binding.
stm8t141 stm8t141 development tools doc id 15699 rev 7 47/50 programming tool figure 29 shows the stm8t141-eval programming tool. to program the device option bytes so that the device can be tested in different configurations, the following materials are available: a programming socket board (stm8t14x-sb). when connected to the programming dongle, this board allows so8 and dfn8 devices as well as plug-in modules delivered in the evaluation kit to be programmed. a programming dongle (st-tslink) and its associated programming software, stvp. figure 29. stm8t141-eval programming tool ordering information table 27. ordering information part number order codes description stm8t141-eval stm8t141-eval stm8t141 evaluation kit stm8t-mod stm8t141am-mod box containing 10 blank modules based on stm8t141am61t (otp device in so8 package) st-tslink st-tslink (1) 1. the st-tslink dongle and the stm8t14x-sb sock et board are not part of the stm8t141-eval evaluation kit, and consequently must be ordered separately. stm8t141 programming dongle stm8t14x-sb stm8t14x-sb (1) stm8t141 socket board programming dongle (st-tslink) programming socket boards (stm8t14x-sb)
revision history stm8t141 48/50 doc id 15699 rev 7 13 revision history table 28. document revision history date revision changes 09-jun-2009 1 initial release. 02-jul-2009 2 v dd range changed to 2.9 to 5.5v. ta b l e 1 2 and table 14 updated. internal voltage regulator bypassed configuration removed. i ddlp removed from table 13 . 31-jul-2009 3 upgraded document from prelim inary data to full datasheet. updated oscillator information in figure 1: stm8t141 block diagram on page 8 . added detection threshold values in table 16: general capacitive sensing characteristics on page 33 . updated values in table 17: response times on page 34 . 05-oct-2009 4 updated section 11: ordering information . section 11.2: orderable favorite device lists : added information on option byte programming; added option list. added section 12: stm8t141 development tools 24-feb-2010 5 lower operating supply voltage changed from 2.9 v to 2.0 v. the following tables were impacted: table 1: device summary , ta bl e 1 2 : operating characteristics , table 13: average current consumption without shield , table 16: general capacitive sensing characteristics , and table 16: general capacitive sensing characteristics . introduced trademark for proxsense (proxsense?) throughout document, ?sensitivity th reshold or level? replaced with ?detection threshold?, ?automatic recalibration? with ?reference freeze timeout?, ?s th ? with ?d th ?, and ?so? with ?so8?. section 2: block diagram : replaced ?capacitive sensing engine? with ?proxsense engine?. added figure 3: ufdfpn8 pinout . updated table 2: stm8t141 pin descriptions . renamed section 4 as stm8t proxsense technology renamed section 4.2 as charge transfer acquisition principle and updated text. figure 5: stm8t measuring circuitry : updated. figure 6: conversion period examples : updated. sections 4.3 renamed section 5: stm8t processing . section re- organised and reworked with new figures and tables added. section 6: typical application diagram : removed introductory text; modified figure 10 , modified footnote 1, added footnote 2, added text regarding r shield resistor, define a touch or proximity detection. section 7: device operation : re-organisation of text; removed reference related to low power modes. section 7.1: option byte description : added reference to section 12 . table 5: option bytes : updated factory default setting of opt1, recalibration timeout renamed reference freeze timeout.
stm8t141 revision history doc id 15699 rev 7 49/50 24-feb-2010 5 cont?d section 7.2.1 , section 7.2.2 , section 7.2.3 , and section 7.2.4 : replaced ?output configuration? with ?output operation?. section 7.2.3: 3-second latch : removed some text concerning the tout/pout pin. renamed section 7.3: detection threshold . section 7.4: power modes : small text changes; ta b l e 8 moved to this section from section 7.4.4: extreme low power mode . section 8.1: shield function : removed text about r shield . figure 20: connecting the shield (coaxial cable implementation) : amended ohm symbol. section 8.2: sensitivity adjustment / added text regarding sensitivity; updated bullet points. added section 8.3: influence of power supply variation . table 12: operating characteristics : added t vdd data. section 9.3.2: average current consumption : for test conditions, ? 100 nf replaced with 47 nf; modified ta bl e 1 3 and note underneath it; added figure 22 . table 14: output pin characteristics : removed t vdd data. added section 9.4: regulator and reference voltage and ta bl e 1 5 . section 9.5: capacitive sensing characteristics : amended ta bl e 1 6 for values of f transfer , t rft , and t burst ; updated symbols for t rft , d th , and ? ; added figure 23 . table 18: external sensing component characteristics : modified c s parameter and r shield min value. section 11: ordering information : updated figure 26 ; added section 11.2 and section 11.3 . section 11.2: orderable favorite device lists : updated ordering part number; added footnote to option list concerning default configuration of opt devices, added packaging information to the option list, updated headings and date. section 12: stm8t141 development tools : replaced stm8t1x1 with stm8t141. 01-apr-2010 6 added that proxsense? is a trademark of azoteq. 28-jun-2011 7 figure 26: stm8t141 ordering information scheme : updated footnote 2. programming tool : replaced stm8t141-sb with stm8t14x-sb. figure 29: stm8t141-eval programming tool : replaced stm8t141-sb with stm8t14x-sb. table 27: ordering information : replaced stm8t1x1-eval and stm8t141-sb with stm8t1 41-eval and stm8t14x-sb respectively. table 28. document revision history (continued) date revision changes
stm8t141 50/50 doc id 15699 rev 7 ? ? ? ? please read carefully: information in this document is provided solely in connection with st products. stmicroelectronics nv and its subsidiaries (?st ?) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described he rein at any time, without notice. all st products are sold pursuant to st?s terms and conditions of sale. purchasers are solely responsible for the choice, selection and use of the st products and services described herein, and st as sumes no liability whatsoever relating to the choice, selection or use of the st products and services described herein. no license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted under this document. i f any part of this document refers to any third party products or services it shall not be deemed a license grant by st for the use of such third party products or services, or any intellectual property contained therein or considered as a warranty covering the use in any manner whatsoev er of such third party products or services or any intellectual property contained therein. unless otherwise set forth in st?s terms and conditions of sale st disclaims any express or implied warranty with respect to the use and/or sale of st products including without limitation implied warranties of merchantability, fitness for a parti cular purpose (and their equivalents under the laws of any jurisdiction), or infringement of any patent, copyright or other intellectual property right. unless expressly approved in writing by an authorized st representative, st products are not recommended, authorized or warranted for use in milita ry, air craft, space, life saving, or life sustaining applications, nor in products or systems where failure or malfunction may result in personal injury, death, or severe property or environmental damage. st products which are not specified as "automotive grade" may only be used in automotive applications at user?s own risk. resale of st products with provisions different from the statements and/or technical features set forth in this document shall immediately void any warranty granted by st for the st product or service described herein and shall not create or extend in any manner whatsoev er, any liability of st. st and the st logo are trademarks or registered trademarks of st in various countries. information in this document supersedes and replaces all information previously supplied. the st logo is a registered trademark of stmicroelectronics. all other names are the property of their respective owners. ? 2011 stmicroelectronics - all rights reserved stmicroelectronics group of companies australia - belgium - brazil - canada - china - czech republic - finland - france - germany - hong kong - india - israel - ital y - japan - malaysia - malta - morocco - philippines - singapore - spain - sweden - switzerland - united kingdom - united states of america www.st.com

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