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MOTOROLA
SEMICONDUCTOR TECHNICAL DATA
Document order number: MC33794/D Rev 6.0, 04/2003
Product Preview Electric Field Imaging Device
The 33794 is intended for applications where noncontact sensing of objects is desired. When connected to external electrodes, an electric field is created. The 33794 is intended for use in detecting objects in this electric field. The IC generates a low-frequency sine wave. The frequency is adjustable by using an external resistor and is optimized for 120 kHz. The sine wave has very low harmonic content to reduce harmonic interference. The 33794 also contains support circuits for a microcontroller unit (MCU) to allow the construction of a two-chip E-field system. Features * Supports up to 9 Electrodes and 2 References * Shield Driver for Driving Remote Electrodes Through Coaxial Cables * +5.0 V Regulator to Power External Circuit * ISO-9141 Physical Layer Interface * Lamp Driver Output * Watchdog and Power ON Reset Timer * Critical Internal Nodes Scaled and Selectable for Measurement * High-Purity Sine Wave Generator Tunable with External Resistor
33794
ELECTRIC FIELD IMAGING DEVICE
DH SUFFIX CASE 1291 44-LEAD HSOP
DWB SUFFIX CASE 1390 54-LEAD SOICW-EP
ORDERING INFORMATION
Device MC33794DH/R2 MC33794DWB/R2 Temperature Range (TA) -40 to 85C -40 to 85C Package 44 HSOP 54 SOICW-EP
33794 Simplified Application Diagram
+12 V
47 F
Indicator Lamp
0.1 F
33794
VPWR
VCC
10 nF Analog_IN Analog_IN Analog_IN Analog_IN Analog_IN
MCU
ISO_Tx ISO_Rx Watchdog Reset GPx
LAMP_OUT LP_CAP VCC LEVEL VDD VDD_MON PWR_MON LAMP_MON ISO-9141 LAMP_SENSE ISO_IN ISO_OUT WD_IN REF_A RST REF_B LAMP_CTRL LAMP_GND TEST E1 E2 SIGNAL
10 k 47 F
ISO-9141 Bus Monitor (Optional)
10 pF 100 pF
1 2 Field Electrodes
Electrode Select Shield Disable
4
A, B, C, D DIS_SHIELD E9 SHIELD GND AGND 9
R_OSC 39 k
This document contains certain information on a new product. Specifications and information herein are subject to change without notice. (c) Motorola, Inc. 2003
A,B,C,D TEST
4
CONTROL LOGIC 22 k (Nominal)
5.6 k OSC E1-E9 + REF_A -REF_B 5.6 k MUX IN MUX OUT
CLK R_OSC 39 k DIS_SHIELD SHIELD 47 k
RECT LP_CAP 10 nF GAIN AND OFFSET
VDD VCC RST WD_IN POR/ WD VCC REG VDD REG
LPF
LEVEL ATTN SIGNAL LAMP_SENSE LAMP_MON
VPWR
AGND GND and HEAT SINK PWR_MON
VDD_MON LAMP_GND LAMP_CTRL ISO_OUT ISO_IN
LAMP CKT ISO-9141
LAMP_OUT ISO-9141
Figure 1. 33794 Internal Block Diagram
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MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
VCC NC AGND SHIELD NC GND TEST E1 E2 E3 E4 E5 E6 E7 E8 E9 REF_A REF_B ISO_OUT ISO_IN ISO-9141 LAMP_OUT
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 HEAT SINK
44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23
VPWR NC VDD VDD_MON CLK R_OSC LP_CAP PWR_MON LEVEL SIGNAL A B C D DIS_SHIELD LAMP_MON LAMP_SENSE NC LAMP_CTRL LAMP_GND WD_IN RST
HSOP PIN FUNCTION DESCRIPTION
Pin 1 2, 5, 27, 43 3 Pin Name VCC NC AGND Formal Name 5.0 V Regulator Output No connect Analog Ground Definition This output pin requires a 47 F capacitor and provides a regulated 5.0 V for the MCU and for internal needs of the 33794. These pins may be used at some future date and should be left open. This pin is connected to the ground return of the analog circuitry. This ground should be kept free of transient electrical noise like that from logic switching. Its path to the electrical current return point should be kept separate from the return for GND. This pin connects to cable shields to cancel cable capacitance. This pin and metal backing is the IC power return and thermal radiator/conductor. This pin is normally connected to circuit ground. There are special operating modes associated with this pin when it is not at ground. These are the electrode pins. They are connected either directly or through coaxial cables to the electrodes for measurements. One of these electrodes can be selected at a time for capacitance measurement. All of the other unselected electrodes are grounded by an internal switch. The signal at the selected electrode pin is routed to the shield driver amplifier by an internal switch. All of the coaxial cable shields should be isolated from ground and connected SHIELD. These pins can be individually selected like E1 through E9. Unlike E1 through E9, these pins are not grounded when not selected. The purpose of these pins is to allow known capacitors to be measured. By using capacitors at the low and high end of the expected range, absolute values for the capacitance on the electrodes can be computed. This pin translates ISO-9141 receive levels to 5.0 V logic levels for the MCU. This pin accepts data from the MCU to be sent over the ISO-9141 communications interface. It translates the 5.0 V logic levels from the MCU to transmit levels on the ISO-9141 bus.
4 6, Heat Sink 7 8-16
SHIELD GND TEST E1-E9
Shield Driver Ground Test Mode Control Electrode Connections
17, 18
REF_A, REF_B
Reference Connections
19 20
ISO_OUT ISO_IN
ISO-9141 Output ISO-9141 Input
MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
GND
33794 3
HSOP PIN FUNCTION DESCRIPTION (continued)
Pin 21 22 Pin Name ISO-9141 LAMP_OUT Formal Name ISO-9141 Bus Lamp Driver Definition This pin connects to the ISO-9141 bus. It provides the drive and detects signaling on the bus and translates it from the bus level to logic levels for the MCU. This is an active low output capable of sinking current of a typical indicator lamp. One end of the lamp should be connected to a positive supply (for example, battery voltage) and the other side to this pin. The current is limited to prevent damage to the IC in the case of a short or surge during lamp turn-on or burn-out. This output is intended to generate the reset function of a typical MCU. It has a delay for power-on reset, level detectors to force a reset when VCC is out-of-range high or low, and a watchdog timer that will force a reset if WD_IN is not asserted at regular intervals. Timing is derived from the oscillator and will change with changes in the resistor attached to R_OSC. This pin must be asserted and deasserted at regular interval in order to prevent RST from being asserted. By having the MCU program perform this operation more often the allowed time, a check that the MCU is running and executing its program is assured. If this doesn't occur, the MCU will be reset. If the watchdog function is not desired, this pin may be connected to CLK to prevent a reset from being issued. This is the ground for the current from the lamp. The current into LAMP_OUT flows out through this pin. This signal is used to control the lamp driver. A high logic level turns on the lamp. This pin is normally connected to the LAMP_OUT pin. The voltage at this pin is reduced and sent to LAMP_MON so the voltage at the lamp pin is brought into the range of the analog-to-digital converter (ADC) in the MCU. This pin is connected through a voltage divider to the LAMP_SENSE pin. The voltage divider scales the voltage at this pin so that battery voltage present when the lamp is off is scaled to the range of the MCU ADC. With the lamp off, this pin will be very close to battery voltage if the lamp is not burned out and the pin is not shorted to ground. This is useful as a lamp check. This pin is used to turn off the shield signal. The purpose of doing this is to be able to detect that the shield signal is not working or the connection to the coax shields is broken. If either of these conditions exists, there will be little or no change in the capacitance measured when the DIS_SHIELD is asserted. If the SHIELD output is working and properly connected, the capacitance of the coax will not be cancelled when this pin is asserted and the measured capacitance will appear to change by approximately the capacitance between the center conductor and the shield in the coax. These input pins control which electrode or reference is active. Selection values are shown in Table 1, Electrode Selection, page 14. This is the undetected signal being applied to the detector. It has a DC level with the low radio frequency signal superimposed on it. Care must be taken to minimize DC loading of this signal. A shift of DC will change the center point of the signal and adversely affect the detection of the signal. This is the detected, amplified, and offset representation of the signal voltage on the selected electrode. Filtering of the rectified signal is performed by a capacitor attached to LP_CAP. This is connected through a voltage divider to VPWR. It allows reduction of the voltage so it will fall within the range of the ADC on the MCU. A capacitor on this pin forms a low pass filter with the internal series resistance from the detector to this pin. This pin can be used to determine the detected level before amplification or offset is applied. A 10 nF capacitor connected to this pin will smooth the rectified signal. More capacitance will increase the response time unnecessarily.
23
RST
Reset
24
WD_IN
Watchdog Input
25 26 28
LAMP_GND LAMP_CTRL LAMP_SENSE
Lamp Ground Lamp Control Lamp Sense
29
LAMP_MON
Lamp Monitor
30
DIS_SHIELD
Shield Driver Disable
34-31 35
A, B, C, D SIGNAL
Selector Inputs Undetected Signal
36
LEVEL
Detected Level
37
PWR_MON
Power Monitor
38
LP_CAP
Low-Pass Filter Capacitor
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MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
HSOP PIN FUNCTION DESCRIPTION (continued)
Pin 39 40 Pin Name R_OSC CLK Formal Name Oscillator Resistor Clock Definition A resistor from this pin to circuit ground determines the operating frequency of the oscillator. The 33794 is optimized for operation around 120 kHz. This pin provides a square wave output at the same frequency as the internal oscillator. The edges of the square wave coincide with the peaks (positive and negative) of the sine wave. This is connected through a voltage divider to VDD. It allows reduction of the voltage so it will fall within the range of the ADC on the MCU. A capacitor is connected to this pin to filter the internal analog regulated supply. This supply is derived from VPWR. 12 V power applied to this pin will be converted to the regulated voltages needed to operate the part. It is also converted to 5.0 V (VCC) and 8.5 V (VDD) to power the MCU and external devices.
41
VDD_MON VDD VPWR
VDD Monitor VDD Capacitor Positive Power Supply Input
42
44
MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
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RST WD_IN NC LAMP_GND NC LAMP_CTRL NC LAMP_SENSE LAMP_MON DIS_SHIELD D C B A SIGNAL LEVEL PWR_MON LP_CAP R_OSC NC NC NC NC CLK VDD_MON VDD VPWR
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28
LAMP_OUT ISO-9414 NC ISO_IN NC NC NC ISO_OUT REF_B REF_A E9 E8 E7 E6 E5 E4 E3 E2 E1 TEST NC NC GND NC SHIELD AGND VCC
SOICW-EP PIN FUNCTION DESCRIPTION
Pin 1 Pin Name RST Formal Name Reset Definition This output is intended to generate the reset function of a typical MCU. It has a delay for power-on reset, level detectors to force a reset when VCC is out-of-range high or low, and a watchdog timer that will force a reset if WD_IN is not asserted at regular intervals. Timing is derived from the oscillator and will change with changes in the resistor attached to R_OSC. This pin must be asserted and deasserted at regular interval in order to prevent RST from being asserted. By having the MCU program perform this operation more often the allowed time, a check that the MCU is running and executing its program is assured. If this doesn't occur, the MCU will be reset. If the watchdog function is not desired, this pin may be connected to CLK to prevent a reset from being issued. These pins may be used at some future date and should be left open.
2
WD_IN
Watchdog In
3, 5, 7, 20-23, 31, 33, 34, 48-50, 52 4 6 8
NC
No connect
LAMP_GND LAMP_CTRL LAMP_SENSE
Lamp Ground Lamp Control Lamp Sense
This is the ground for the current from the lamp. The current into LAMP_OUT flows out through this pin. This signal is used to control the lamp driver. A high logic level turns on the lamp. This pin is normally connected to the LAMP_OUT pin. The voltage at this pin is reduced and sent to LAMP_MON so the voltage at the lamp pin is brought into the range of the analog-to-digital converter (ADC) in the MCU. This pin is connected through a voltage divider to the LAMP_SENSE pin. The voltage divider scales the voltage at this pin so that battery voltage present when the lamp is off is scaled to the range of the MCU ADC. With the lamp off, this pin will be very close to battery voltage if the lamp is not burned out and the pin is not shorted to ground. This is useful as a lamp check.
9
LAMP_MON
Lamp Monitor
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MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
SOICW-EP PIN FUNCTION DESCRIPTION (continued)
Pin 10 Pin Name DIS_SHIELD Formal Name Shield Driver Definition This pin is used to turn off the shield signal. The purpose of doing this is to be able to detect that the shield signal is not working or the connection to the coax shields is broken. If either of these conditions exists, there will be little or no change in the capacitance measured when the DIS_SHIELD is asserted. If the SHIELD output is working and properly connected, the capacitance of the coax will not be cancelled when this pin is asserted and the measured capacitance will appear to change by approximately the capacitance between the center conductor and the shield in the coax. These input pins control which electrode or reference is active. Selection values are shown in Table 1, Electrode Selection, page 14. This is the undetected signal being applied to the detector. It has a DC level with the low radio frequency signal superimposed on it. Care must be taken to minimize DC loading of this signal. A shift of DC will change the center point of the signal and adversely affect the detection of the signal. This is the detected, amplified, and offset representation of the signal voltage on the selected electrode. Filtering of the rectified signal is performed by a capacitor attached to LP_CAP. This is connected through a voltage divider to VPWR. It allows reduction of the voltage so it will fall within the range of the ADC on the MCU. A capacitor on this pin forms a low pass filter with the internal series resistance from the detector to this pin. This pin can be used to determine the detected level before amplification or offset is applied. A 10 nF capacitor connected to this pin will smooth the rectified signal. More capacitance will increase the response time unnecessarily. A resistor from this pin to circuit ground determines the operating frequency of the oscillator. The 33794 is optimized for operation around 120 kHz. This pin provides a square wave output at the same frequency as the internal oscillator. The edges of the square wave coincide with the peaks (positive and negative) of the sine wave. This is connected through a voltage divider to VDD. It allows reduction of the voltage so it will fall within the range of the ADC on the MCU. A capacitor is connected to this pin to filter the internal analog regulated supply. This supply is derived from VPWR. 12 V power applied to this pin will be converted to the regulated voltages needed to operate the part. It is also converted to 5.0 V (VCC) and 8.5 V (VDD) to power the MCU and external devices. This output pin requires a 47 F capacitor and provides a regulated 5.0 V for the MCU and for internal needs of the 33794. This pin is connected to the ground return of the analog circuitry. This ground should be kept free of transient electrical noise like that from logic switching. Its path to the electrical current return point should be kept separate from the return for GND. This pin connects to cable shields to cancel cable capacitance. This pin and metal backing is the IC power return and thermal radiator/conductor. This pin is normally connected to circuit ground. There are special operating modes associated with this pin when it is not at ground.
14-11 15
A, B, C, D SIGNAL
Selector Inputs Undetected Signal
16
LEVEL
Detected Level
17
PWR_MON
Power Monitor
18
LP_CAP
Low-Pass Filter Capacitor
19 24
R_OSC CLK
Oscillator Resistor Clock
25
VDD_MON VDD VPWR
VDD Monitor VDD Capacitor Positive Power Supply
26
27
28 29
VCC AGND
5.0 V Regulator Output Analog Ground
30 32 35
SHIELD GND TEST
Shield Driver Ground Test Mode Control
MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
33794 7
SOICW-EP PIN FUNCTION DESCRIPTION (continued)
Pin 36-44 Pin Name E1-E9 Formal Name Electrode Connections Definition These are the electrode pins. They are connected either directly or through coaxial cables to the electrodes for measurements. One of these electrodes can be selected at a time for capacitance measurement. All of the other unselected electrodes are grounded by an internal switch. The signal at the selected electrode pin is routed to the shield driver amplifier by an internal switch. All of the coaxial cable shields should be isolated from ground and connected SHIELD. These pins can be individually selected like E1 through E9. Unlike E1 through E9, these pins are not grounded when not selected. The purpose of these pins is to allow known capacitors to be measured. By using capacitors at the low and high end of the expected range, absolute values for the capacitance on the electrodes can be computed. This pin translates ISO-9141 receive levels to 5.0 V logic levels for the MCU. This pin accepts data from the MCU to be sent over the ISO-9141 communications interface. It translates the 5.0 V logic levels from the MCU to transmit levels on the ISO-9141 bus. This pin connects to the ISO-9141 bus. It provides the drive and detects signaling on the bus and translates it from the bus level to logic levels for the MCU. This is an active low output capable of sinking current of a typical indicator lamp. One end of the lamp should be connected to a positive supply (for example, battery voltage) and the other side to this pin. The current is limited to prevent damage to the IC in the case of a short or surge during lamp turn-on or burn-out.
45, 46
REF_A, REF_B
Reference Connections
47 51
ISO_OUT ISO_IN
ISO-9141 Output ISO-9141 Input
53 54
ISO-9141 LAMP_OUT
ISO-9141 Bus Lamp Driver
33794 8
MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
MAXIMUM RATINGS All voltages are with respect to ground unless otherwise noted.
Rating Peak VPWR Voltage Double Battery 1 Minute Maximum TA = 30C ESD Voltage Human Body Model (Note 1) Machine Model (Note 2) Storage Temperature Operating Ambient Temperature Operating Junction Temperature Thermal Resistance Junction-to-Ambient (Note 3) Junction-to-Case (Note 4) Junction-to-Board (Note 5) Soldering Temperature (for 10 Seconds) RJ-A RJ-C RJ-B TSOLDER 41 0.2 3.0 260 C VESD1 VESD2 TSTG TA TJ 2000 200 -55 to 150 -40 to 85 -40 to 150 C C C C/W Symbol VPWRPK VDBLBAT 26.5 V Value 40 Unit V V
Notes 1. ESD1 performed in accordance with the Human Body Model (CZAP = 100 pF, RZAP = 1500 ). 2. 3. ESD2 performed in accordance with the Machine Model (CZAP = 200 pF, RZAP = 0 ). Junction temperature is a function of on-chip power dissipation, package thermal resistance, mounting site (board) temperature, ambient temperature, air flow, power dissipation of other components on the board, and board thermal resistance. In accordance with SEMI G38-87 and JEDEC JESD51-2 with the single layer board horizontal. Indicates the average thermal resistance between the die and the case top surface as measured by the cold plate method (MILSPEC 883 Method 1012.1) with the cold plate temperature used for the case temperature. Thermal resistance between the die and the printed circuit board per JEDEC JESD51-8. Board temperature is measured on the top surface of the board near the package.
4. 5.
MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
33794 9
STATIC ELECTRICAL CHARACTERISTICS Characteristics noted under condition -40C TJ 150C. Voltages are relative to GND unless otherwise noted.
Characteristic Symbol Min Typ Max Unit
VOLTAGE REGULATORS
5.0 V Regulator Voltage 7.0 V VPWR 18 V, 1.0 mA IL 75 mA, CFILT = 47 F Analog Regulator Voltage 9.0 V VPWR 18 V, CFILT = 47 F VANALOG 8.075 8.5 8.925 VCC 4.75 5.0 5.25 V V
VCC OUT-OF-RANGE VOLTAGE DETECTOR
5.0 V Low Voltage Detector 5.0 V High Voltage Detector 5.0 V Out-of-Range Voltage Detector Hysteresis VLV5 VHV5 VHYS5 4.0 5.26 - 4.52 5.55 0.05 4.72 5.83 - V V V
ISO-9141 COMMUNICATIONS INTERFACE
Input Low Level (Note 6) Input High Level (Note 6) Input Hysteresis (Note 6) Output Low (Note 6) Output High (Note 6) Output Breakdown IOUT = 20 mA Output Resistance IOUT = 40 mA Current Limit Sinking Current with VOUT < 0.3 VPWR IN Output Propagation Delay Out to ISO-9141, CLOAD = 20 pF TIFDLY - - 8.0 IIFLIM 60 90 120 s RIFON - 58 - mA VIFINLO VIFINHI VIFINHYS VIFOLO VIFOHI VIFZ 40 - - 0.30 - - - 0.8 0.33 0.53 0.2 - - - 0.7 - 0.2 - V/V V/V V/V V/V V/V V
ISO IN
Logic Output Low ISINK = 1.0 mA Logic Output Pull-Up Current VOUT = 0 V Input to Output Propagation Delay ISO-9141 to ISO_IN, RL = 10 k, CL = 470 pF, 7.0 V VPWR 18 V Notes 6. Ratio to VPWR. TIFDLY - - 5.4 IIFPU 100 - - s VIFOLO - - 1.0 A V
33794 10
MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
STATIC ELECTRICAL CHARACTERISTICS (continued) Characteristics noted under condition -40C TJ 150C. Voltages are relative to GND unless otherwise noted.
Characteristic Symbol Min Typ Max Unit
ELECTRODE SIGNALS
Total Variance Between Electrode Measurements (Note 7) All CLOAD = 15 pF Electrode Maximum Harmonic Level Below Fundamental (Note 8) 5.0 pF CLOAD 100 pF Electrode Transmit Output Range 5.0 pF CLOAD 100 pF Receive Input Voltage Range Grounding Switch on Voltage ISW = 1.0 mA RXV SWVON - - 5.0 ELTXV 1.0 0 - - 8.0 9.0 V V ELHARM - -20 - V ELVVAR - - 3.0 dB %
SHIELD DRIVER
Shield Driver Output Level 0 pF CLOAD 500 pF Shield Driver Input Range Grounding Switch on Voltage (Note 9) SDIN SWVON SDTXV 1.0 0 - - - - 8.0 9.0 1.5 V V V
LOGIC I/O
CMOS Logic Input Low Threshold Logic Input High Threshold Voltage Hysteresis Input Current VIN = VCC VIN = 0 V VTHL VTHH VHYS IIN 10 -5.0 - - 50 5.0 0.3 - - - - 0.06 - 0.7 - VCC VCC VCC A
SIGNAL DETECTOR
Detector Output Resistance LP_CAP to LEVEL Gain LP_CAP to LEVEL Offset Notes 7. Verified by design. Not tested in production. 8. Verified by design and characterization. Not tested in production. 9. Current into grounded pin under test = 1.0 mA. DETRO AREC VRECOFF - 3.6 -3.3 50 4.0 -3.0 - 4.4 -2.7 k AV V
MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
33794 11
STATIC ELECTRICAL CHARACTERISTICS (continued) Characteristics noted under condition -40C TJ 150C. Voltages are relative to GND unless otherwise noted.
Characteristic Symbol Min Typ Max Unit
LAMP DRIVER
On Resistance IIN = 400 mA Current Limit VOUT = 1.0 V On-Voltage IOUT = 400 mA Breakdown Voltage IOUT = 100 A, Lamp Off VLDZ 40 - - VLDON - - 1.4 V ILDLIM 0.7 - 1.7 V RLDDSON - 1.75 3.5 A
VOLTAGE MONITORS
LAMP_MON to LAMP_SENSE Ratio PWR_MON to VPWR Ratio VDD_MON to VDD Ratio LMPMON PWRMON VDDMON 0.1950 0.2200 0.45 0.20524 0.2444 0.5 0.2155 0.2688 0.55 V/V V/V V/V
33794 12
MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
DYNAMIC ELECTRICAL CHARACTERISTICS Characteristics noted under condition -40C TJ 150C. Voltages are relative to GND unless otherwise noted.
Characteristic Symbol Min Typ Max Unit
OSC
OSC Frequency Stability (Note 10), (Note 11) OSC Center Frequency R_OSC = 39 k Harmonic Content (Note 10) 2nd through 4th Harmonic Level 5th and Higher OSCHARM - - - - -20 -60 f STAB f OSC - 120 - dB - - 10 % kHz
SHIELD DRIVER
Shield Driver Maximum Harmonic level below Fundamental (Note 10) 10 pF CLOAD 500 pF Shield Driver Gain Bandwidth Product (Note 10) Measured at 120 kHz SDGBW - 4.5 - SDHARM - -20 - MHz dB
POR
POR Time-Out Period t PER 9.0 - 50 ms
WATCHDOG
Watchdog Time-Out Period Watchdog Reset Hold Time t WDPER t WDHLD 50 9.0 68 - 250 50 ms ms
LAMP DRIVER
Short Circuit to Battery Survival Time Notes 10. Verified by design and characterization. Not tested in production. 11. Does not include errors in external reference parts. t SCB 3.0 - - ms
MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
33794 13
Table 1. Electrode Selection
PIN/SIGNAL Source (internal) E1 E2 E3 E4 E5 E6 E7 E8 E9 REF_A REF_B Internal OSC Internal OSC after 22 k Internal Ground Reserved D 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 C 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 B 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 A 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
33794 14
MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
SYSTEM/APPLICATION INFORMATION
INTRODUCTION
The 33794 is intended for use in detecting objects using an electric field. The IC generates a low radio frequency sine wave. The frequency is set by an external resistor and is optimized for 120 kHz. The sine wave has very low harmonic content to reduce potential interference at higher harmonically related frequencies. The internal generator produces a nominal 5.0 V peak-to-peak output that is passed through an internal resistor of about 22 k. An internal multiplexer routes the signal to one of 11 pins under control of the ABCD input pins. A receiver multiplexer simultaneously connected to the selected electrode routes its signal to a detector, which converts the sine wave to a DC level. This DC level is filtered by an external capacitor and is multiplied and offset to increase sensitivity. All of the unselected electrode outputs are grounded by the device. The current flowing between the selected electrode and the other grounded electrodes plus other grounded objects around the electrode causes a voltage drop across the internal resistance. Objects brought into or out of the electric field change the current and resulting voltage at the IC pin, which in turn reduces the voltage at LP_CAP and LEVEL. A shield driver is included to minimize the effect of capacitance caused by using coaxial cables to connect to remote electrodes. By driving the coax shield with this signal, the shield voltage follows that of the center conductor, significantly reducing the effective capacitance of the coax and maintaining sensitivity to the capacitance at the electrode. The 33794 is made to work with and support a microcontroller. It provides two voltage regulators, a power-onreset/out-of-range voltage detector, watchdog circuit, lamp driver and sense circuit, and a physical layer ISO-9141 communications interface.
BLOCK DIAGRAM COMPONENTS
Refer to Figure 1, 33794 Internal Block Diagram, page 2, for a graphic representation of the block diagram information in this section. OSC This section generates a high purity sine wave. The center frequency is controlled by a resistor attached to R_OSC. The normal operating frequency is around 120 kHz. A square wave version of the frequency output is available at CLK. Timing for the power-on reset and watchdog (POR/WD) circuit are derived from this oscillator's frequency. MUX OUT This circuit directs the output of the sine wave to one of nine possible electrode outputs or two reference pins. All unused pins are automatically grounded. The selected output is controlled by the ABCD inputs. MUX IN This circuit connects the selected electrode, reference, or one of two internal nodes to an amplifier/detector. The selection is controlled by the ABCD inputs and follows the driven electrode/reference when one is selected. RECT The rectifier circuit detects the level from MUX IN by offsetting the midpoint of the sine wave to zero volts and inverting the waveform when it is below the midpoint. It is important to avoid DC loading of the signal, which would cause a shift in the midpoint voltage of the signal from the MUX IN. LPF The rectified sine wave is filtered by a low pass function in the LPF formed by an internal resistance and an external capacitance attached to LP_CAP. The nominal value of the internal resistance is 50 k. The value of the external capacitor is selected to provide filtering of noise while still allowing the desired settling time for the detector output. A 10 nF capacitor would allow 99% settling in less than 5.0 ms. GAIN and OFFSET This circuit multiplies the detected and filtered signal by a gain and offsets the result by a DC level. This results in an output range that covers 1.0 V to 4.0 V for capacitive loading of the field in the range of 10 pF to 100 pF. This allows higher sensitivity for a digital-to-analog converter with a 0 V-to-5.0 V input range. ATTN This circuit passes the undetected signal to SIGNAL for external use. LAMP CKT This section controls the operation of the LAMP_OUT pin. When LAMP_CTRL is asserted, LAMP_OUT is pulled to LAMP_GND. If one side of an indicator lamp or LED (with appropriate current setting resistor) is connected to a positive voltage source and the other is connected to LAMP_OUT, and LAMP_GND is connected to ground, the lamp will light. This circuit provides current limiting to prevent damage to itself in the case of a shorted lamp or during a high-surge condition typical of an incandescent lamp burnout.
MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
33794 15
ISO-9141 This circuit connects to an ISO-9141 bus to allow remote communications. ISO_IN is data from the bus to the MCU and ISO_OUT is data to drive onto the bus from the MCU. POR/WD This circuit is a combined power-on reset and watchdog timer. The RST output is held low until a certain amount of time after the VCC output has remained above a minimum operating threshold. If VCC falls below the level at any time, RST is pulled low again and held until the required time after VCC has returned high. An overvoltage circuit is also included, which will force a reset if VCC rises above a maximum voltage. The watchdog function also can force RST low if too long an interval is allowed to pass between positive transitions on WD_IN. VCC REG This circuit converts an unregulated voltage from VIN to a regulated 5.0 V source, which is used internally and available for other components requiring a regulated voltage source.
VDD REG This is a regulator for analog devices that require more than 5.0 V. This is used by the device and some current is available to operate op-amps and other devices. By having this higher voltage available, some applications can avoid the need for a rail-to-rail output amplifier and still achieve the 0 V-to-5.0 V output for a digital-to-analog converter input. VDDMON is a divided output from VDD, which allows a 0 V-to-5.0 V ADC to measure VDD. CONTROL LOGIC This contains the logic that decodes and controls the MUXes and some of the test modes.
APPLICATION INFORMATION
The 33794 is intended to be used where an object's size and proximity are to be determined. This is done by placing electrodes in the area where the object will be. The proximity of an object to an electrode can be determined by the increase in effective capacitance as the object gets closer to the electrode and modifies the electric field between the electrode and surrounding electrically common objects. The shape and size of an object can be determined by using multiple electrodes over an area and observing the capacitance change on each of the electrodes. Those that don't change have nothing near them, and those that do change have part of the object near them. The voltage measured is an inverse function of the capacitance between the electrode being measured and the surrounding electrodes and other objects in the electric field surrounding the electrode. Increasing capacitance results in decreasing voltage. The value of series resistance (22 k) was chosen to provide a nearly linear relationship at 120 kHz over a range of 10 pF to 100 pF. The measured value will change with any change in frequency, series resistance, driving voltage, or detector sensitivity. These can change with temperature and time. The proper use of REF_A and REF_B will allow much of the changes to be compensated for. A typical measurement algorithm would start by measuring the voltage for two known value capacitors (attached to REF_A and REF_B). The value of these capacitors would be chosen to be near the minimum and maximum values of capacitance expected to be seen at the electrodes. These reference voltages and the known capacitance values are then used with the electrode measurement voltage to determine the capacitance seen by the electrode. This method can be used to detect short- and long-term changes due to objects in the electric field and significantly reduce the effect of temperatureand time-induced changes. The 33794 does not contain an ADC. It is intended to be used with an MCU that contains one. Offset and gain have been added to the 33794 to maximize the sensitivity over the range of 0 pF to 100 pF. An 8-bit ADC can resolve around 0.4 pF of change and a 10-bit converter around 0.1 pF. Higher resolution results in more distant detection of smaller objects. DC loading on the electrodes should be avoided. The signal is generated with a DC offset that is more than half the peak-topeak level. This keeps the signal positive above ground at all times. The detector uses this voltage level as the midpoint for detection. All signals below this level are inverted and added to all signals above this level. Loading of the DC level will cause some of the positive half of the signal to be inverted and added and will change the measurement. If it is not possible to assure that the electrodes will always have a high DC resistance to ground or a voltage source, a series capacitor of about 10 nF should be connected between the IC electrode pins and the electrodes.
33794 16
MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
PACKAGE DIMENSIONS
DH SUFFIX 44-LEAD HSOP PLASTIC PACKAGE CASE 1291-01 ISSUE O
PIN ONE ID
h
X 45
E3 E2
4X
E5
1
44
D 0.325
22
23
EXPOSED HEATSINK AREA
B
E1
22X
E bbb M C B Y A A2
A
E4 BOTTOM VIEW
NOTES: 1. CONTROLLING DIMENSION: MILLIMETER. 2. DIMENSIONS AND TOLERANCES PER ASME Y14.5M, 1994. 3. DATUM PLANE -H- IS LOCATED AT BOTTOM OF LEAD AND IS COINCIDENT WITH THE LEAD WHERE THE LEAD EXITS THE PLASTIC BODY AT THE BOTTOM OF THE PARTING LINE. 4. DIMENSIONS D AND E1 DO NOT INCLUDE MOLD PROTRUSION. ALLOWABLE PROTRUSION IS 0.150 PER SIDE. DIMENSIONS D AND E1 DO INCLUDE MOLD MISMATCH AND ARE DETERMINED AT DATUM PLANE -H-. 5. DIMENSION b DOES NOT INCLUDE DAMBAR PROTRUSION. ALLOWABLE DAMBAR PROTRUSION SHALL BE 0.127 TOTAL IN EXCESS OF THE b DIMENSION AT MAXIMUM MATERIAL CONDITION. 6. DATUMS -A- AND -B- TO BE DETERMINED AT DATUM PLANE -H-. 7. DIMENSION D DOES NOT INCLUDE TIEBAR PROTRUSIONS. ALLOWABLE TIEBAR PROTRUSIONS ARE 0.150 PER SIDE. MILLIMETERS MIN MAX 3.000 3.400 0.025 0.125 2.900 3.100 15.800 16.000 11.700 12.600 0.900 1.100 --- 1.000 13.950 14.450 10.900 11.100 2.500 2.700 6.400 7.300 2.700 2.900 --- 1.000 0.840 1.100 0.350 BSC 0.220 0.350 0.220 0.320 0.230 0.320 0.230 0.280 0.650 BSC --- 0.800 0 8 0.200 0.100
D2
42X
e
D3 H
DATUM PLANE
b1 c C
SEATING PLANE
D1
4X
c1 b aaa
M
CA
GAUGE PLANE
SECTION W-W L1 W L (1.600) DETAIL Y W A1
bbb C
q
DIM A A1 A2 D D1 D2 D3 E E1 E2 E3 E4 E5 L L1 b b1 c c1 e h q aaa bbb
MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
33794 17
DWB SUFFIX 54-LEAD SOICW-EP PLASTIC PACKAGE CASE 1390-01 ISSUE B
10.3 5 7.6 7.4 C 9 B 2.65 2.35
52X
1
54
0.65
PIN 1 INDEX
4 9 B B 18.0 17.8 C L
27
28
5.15
2X 27 TIPS
A
54X
SEATING PLANE
0.3
ABC
0.10 A
NOTES: 1. ALL DIMENSIONS ARE IN MILLIMETERS. 2. DIMENSIONING AND TOLERANCING PER ASME Y14.5M, 1994. 3. DATUMS B AND C TO BE DETERMINED AT THE PLANE WHERE THE BOTTOM OF THE LEADS EXIT THE PLASTIC BODY. 4. THIS DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSION OR GATE BURRS. MOLD FLASH, PROTRUSION OR GATE BURRS SHALL NOT EXCEED 0.15 MM PER SIDE. THIS DIMENSION IS DETERMINED AT THE PLANE WHERE THE BOTTOM OF THE LEADS EXIT THE PLASTIC BODY. 5. THIS DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH AND PROTRUSIONS SHALL NOT EXCEED 0.25 MM PER SIDE. THIS DIMENSION IS DETERMINED AT THE PLANE WHERE THE BOTTOM OF THE LEADS EXIT THE PLASTIC BODY. 6. THIS DIMENSION DOES NOT INCLUDE DAMBAR PROTRUSION. ALLOWABLE DAMBAR PROTRUSION SHALL NOT CAUSE THE LEAD WIDTH TO EXCEED 0.46 MM. DAMBAR CANNOT BE LOCATED ON THE LOWER RADIUS OR THE FOOT. MINIMUM SPACE BETWEEN PROTRUSION AND ADJACENT LEAD SHALL NOT LESS THAN 0.07 MM. 7. EXACT SHAPE OF EACH CORNER IS OPTIONAL. 8. THESE DIMENSIONS APPLY TO THE FLAT SECTION OF THE LEAD BETWEEN 0.1 MM AND 0.3 MM FROM THE LEAD TIP. 9. THE PACKAGE TOP MAY BE SMALLER THAN THE PACKAGE BOTTOM. THIS DIMENSION IS DETERMINED AT THE OUTERMOST EXTREMES OF THE PLASTIC BODY EXCLUSIVE OF MOLD FLASH, TIE BAR BURRS, GATE BURRS AND INTER-LEAD FLASH, BUT INCLUDING ANY MISMATCH BETWEEN THE TOP AND BOTTOM OF THE PLASTIC BODY.
A R0.08 MIN C A 8 0 0.9 0.5 SECTION B-B 0.1 0.0 C 0.25
GAUGE PLANE
0 MIN
(1.43)
0.30 A B C 4.8 4.3
(0.29) 0.30 0.25 0.38 0.22 0.13
M
BASE METAL
4.8 4.3 0.30 A B C
(0.25)
6
PLATING
A BC
8
SECTION A-A ROTATED 90 CLOCKWISE VIEW C-C
33794 18
MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
NOTES
MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
33794 19
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