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| Data Sheet STC705-706/706P-707-708-708T/S/R-813L P Supervisor Circuits -------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Features * Precision supply-voltage monitor - 4.63V (STC706L/705, 813L, 708L/707) - 4.38V (STC706M/706, 813M, 708M/708) - 3.08V (STC706T, 813T, 708T) - 2.93V (STC706S, 813S, 708S) - 2.63V (STC706R, 813R/706P, 708R) - 2.32V (STC706Z, 813Z, 708Z) - 2.20V (STC706Y, 813Y, 708Y) * 200ms reset pulse width * Debounced TTL/CMOS-compatible manualreset input * Independent watchdog timer 1.6sec time-out (not available for STC707/708/708T/708S/R/Z/Y) * Reset output signal: - Active-low only (STC705/706/706T/S/R/Z/Y) - Active-high only (STC813L/M/T/S/R/706P) - Active-high and active-low (707/708/708T/S/R) * Voltage monitor for power-fail or low battery warning * Guaranteed RESET/RESET valid at VCC = 1.2V Introduction The STC706X/813X/708X family microprocessor (P) supervisory circuits are targeted to improve reliability and accuracy of power-supply circuitry in P systems. These devices reduce the complexity and number of components required to monitor powersupply and battery functions. The main functions are: 1. Asserting reset output during power-p, powerdown and brownout conditions for P system; 2. Detecting power failure or low-battery conditions with a 1.25V threshold detector; 3. Watchdog functions (not for STC708x). Applications * Power-supply circuitry in P systems STC 1 Ver1.0 Data Sheet STC705-706/706P-707-708-708T/S/R-813L P Supervisor Circuits -------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Contents Features ....................................................................................................................................................... 1 Block Diagram ............................................................................................................................................ 1 Introduction ................................................................................................................................................. 1 Pin Information ........................................................................................................................................... 4 Pin Configuration .............................................................................................................................. 4 Pin Description .................................................................................................................................. 4 Functional Description ................................................................................................................................ 5 Reset Output ...................................................................................................................................... 5 Watchdog Timer ................................................................................................................................ 5 Manual Reset ..................................................................................................................................... 5 Power-Fail Comparator ..................................................................................................................... 5 Function Reference Table .................................................................................................................. 6 Detailed Specifications ................................................................................................................................ 7 Absolute Maximum Ratings .............................................................................................................. 7 Recommended Operation Condition ................................................................................................. 7 DC Electrical Characteristics ............................................................................................................. 8 AC Electrical Characteristics ............................................................................................................. 9 Ordering Information ................................................................................................................................ 10 Mechanical Information ............................................................................................................................ 11 Notes ......................................................................................................................................................... 12 STC 2 Ver1.0 Data Sheet STC705-706/706P-707-708-708T/S/R-813L P Supervisor Circuits -------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Block Diagram Figure 1. Block Diagram of STC706X/707, STC813X/706P WDI Watchdog Transition Detector Vcc 250uA Watchdog Timer WDO Timebase for Reset & Watchdog MR Reset Generator Vcc RESET *706X (RESET *813X,706P) V RST PFI 1.25V PFO Figure 2. Block Diagram of STC708X / 707 Vcc 250uA MR Reset Generator Vcc RESET RESET VRST PFI PFO 1.25V STC 3 Ver1.0 Data Sheet STC705-706/706P-707-708-708T/S/R-813L P Supervisor Circuits -------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Pin Information Pin Configuration Figure 3. Pin Configuration STC706L/M/T/S/RESA STC706L/M/T/S/REPA 8-Pin SOIC/8-Pin PDIP MR V CC GND PFI 1 2 3 4 8 7 6 5 WDO RESET WDI PFO MR V CC GND PFI STC813L/M/T/S/R/706PESA STC813L/M/T/S/R/706PEPA 8-Pin SOIC/8-Pin PDIP 1 2 3 4 8 7 6 5 WDO RESET WDI PFO MR V CC GND PFI STC708L/M/T/S/RESA STC708L/M/T/S/REPA 8-Pin SOIC/8-Pin PDIP 1 2 3 4 8 7 6 5 RESET RESET NC PFO Top View Pin Description Table 1. Pin Description P in Na m e MR Vcc GND PFI PFO Typ e I Power Ground I O Descr ip t ion Ma n u a l-R eset : triggers a reset pulse when pulled below 0.8V, active low. It has an internal 250A pull-up current and be driven from a TTL or CMOS logic line as well as shorted to ground with a switch. Power Su p p ly G r ou n d R efer en ce for all signals Power -Fa il Volt a ge Mon it or I n p u t: When PFI is less than 1.25V, PFO goes low. Connect PFI to GND or Vcc when not used. Power -Fa il O u t p u t : it gets low and sinks current when PFI is less than 1.25V; otherwise PFO stays high. Wa t ch d og I n p u t: If WDI remains high or low for 1.6sec, the internal watchdog timer runs out and WDO goes low. Floating WDI or connecting WDI to a high-impedance three-state buffer disables the watchdog feature. The internal watchdog timer clears whenever reset is asserted. WDI is threestated, or WDI sees a rising or falling edge. No C on n ect O R eset O u t p u t p u lses: low for 200ms when triggered, and stays low whenever Vcc is below the reset threshold. It remains low for 200ms after Vcc rises above the reset threshold or MR goes from low to high. A watchdog timeout will not trigger RESET unless WDO is connected to MR. Wa t ch d og O u t p u t : pulls low when the internal watchdog timer finishes its 1.6sec count and does not go high again until the watchdog is cleared. WDO also goes low during low-line conditions. Whenever Vcc is below the reset threshold, WDO stays low; however, unlike RESET, WDO does not have minimum pulse width. As soon as Vcc rises above the reset threshold, WDO goes high with no delay. T h e inver se of R E SE T: active high. Whenever RESET is high, RESET is low. WDI I NC RESET WDO O RESET STC O 4 Ver1.0 Data Sheet STC705-706/706P-707-708-708T/S/R-813L P Supervisor Circuits -------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Functional Description The STCxxx family can assert reset output during power-up, power-down and brownout conditions for uP system, detect power failure or low-battery conditions with a 1.25V threshold detector and have watchdog functions. Refer to Table 2 for their individual features. The typical application see Figure 4. Watchdog Timer The watchdog circuit monitors the P's activity. If the P does not toggle the watchdog input (WDI) within 1.6sec and WDI is not in high impedance, WDO goes low. As long as RESET is asserted or the WDI input is in high impedance, the watchdog timer will stay cleared and will not count. As soon as reset is released and WDI is driven high or low, the timer will start counting. Pulses as short as 50ns can be detected. Typically, WDO will be connected to the non-maskable interrupt input (NMI) of a P. When VCC drops below the reset threshold, WDO will go low whether or not the watchdog timer has timed out yet. Normally this would trigger an NMI interrupt, but RESET goes low simultaneously, and thus overrides the NMI interrupt. If WDI is left unconnected, WDO can be used as a low-line output. Since floating WDI disables the internal timer, WDO goes low only when VCC falls below the reset threshold, thus functioning as a low-line output. Reset Output The supervisory circuits can assert reset for a microprocessor during power-up, power-down and brownout to prevent code execution errors. On power-up, once VCC reaches about 1.2V, RESET is a guaranteed logic low of 0.4V or less. As VCC rises, RESET stays low. When VCC rises above the reset threshold, an internal timer releases RESET after about 200ms. RESET pulses low whenever VCC drops below the reset threshold (brownout condition). If brownout occurs in the middle of a previously initiated reset pulse, the pulse continues for at least another 140ms. On power-down, once VCC falls below the reset threshold, RESET stays low and is guaranteed to be 0.4V or less until Vcc drops below 1V. The STC813x and STC706P active-high RESET output is simply the complement of the RESET output, and is guaranteed to be valid with VCC down to 1.2V. Some Ps, such as Intel's 80C51, require an active-high reset pulse. Manual Reset The manual-reset input (MR) allows reset to be triggered by a push-button switch. The switch is effectively debounced by the 140ms minimum reset pulse width. MR is TTL/CMOS logic compatible, so it can be driven by any logic reset output. Power-Fail Comparator The power-fail comparator will send out a Low signal once detects a voltage lowered than 1.25V. It can be used for various purposes because its output and non-inverting input are not internally connected. The inverting input is internally connected to a 1.25V reference. Figure 4. Typical Application Circuit IN DC Linear Regulator OUT Vcc RESET P Supervisory Circuit PFI WDI WDO MR PFO Vcc RESET I/O Line NMI Interrupt P STC 5 Ver1.0 Data Sheet STC705-706/706P-707-708-708T/S/R-813L P Supervisor Circuits -------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Function Reference Table Table 2. Function Table of PT7A75xx Family Part No. STC706L/705 STC813L STC708L/707 STC706M/706 STC813M STC708M/708 STC706T STC813T STC708T STC706S STC813S STC708S STC706R STC813R/706P STC708R STC706Z STC813Z STC708Z STC706Y STC813Y STC708Y Reset Threshold 4.63V 4.63V 4.63V 4.38V 4.38V 4.38V 3.08V 3.08V 3.08V 2.93V 2.93V 2.93V 2.63V 2.63V 2.63V 2.32V 2.32V 2.32V 2.20V 2.20V 2.20V Reset Active Low Nom. Reset Time Nom. Watch dog or High (ms), t RS Time (sec), t WD LOW HIGH LOW, HIGH LOW HIGH LOW, HIGH LOW HIGH LOW, HIGH LOW HIGH LOW, HIGH LOW HIGH LOW, HIGH LOW HIGH LOW, HIGH LOW HIGH LOW, HIGH 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 1.6 1.6 unavailable 1.6 1.6 unavailable 1.6 1.6 unavailable 1.6 1.6 unavailable 1.6 1.6 unavailable 1.6 1.6 unavailable 1.6 1.6 unavailable Power Fail Comp. 1.25V detector 1.25V detector 1.25V detector 1.25V detector 1.25V detector 1.25V detector 1.25V detector 1.25V detector 1.25V detector 1.25V detector 1.25V detector 1.25V detector 1.25V detector 1.25V detector 1.25V detector 1.25V detector 1.25V detector 1.25V detector 1.25V detector 1.25V detector 1.25V detector Manual Reset Input Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes STC 6 Ver1.0 Data Sheet STC705-706/706P-707-708-708T/S/R-813L P Supervisor Circuits -------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Mechanical Information Figure 7. 8-Pin SOIC STC 8 Ver1.0 |
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