Data Sheet STC705-706/706P-707-708-708T/S/R-813L µP Supervisor Circuits -------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Features Introduction • Precision supply-voltage monitor The STC706X/813X/708X family microprocessor - 4.63V (STC706L/705, 813L, 708L/707) (µP) supervisory circuits are targeted to improve - 4.38V (STC706M/706, 813M, 708M/708) reliability and accuracy of power-supply circuitry in - 3.08V (STC706T, 813T, 708T) µP systems. These devices reduce the complexity and - 2.93V (STC706S, 813S, 708S) number of components required to monitor power- - 2.63V (STC706R, 813R/706P, 708R) supply and battery functions. - 2.32V (STC706Z, 813Z, 708Z) The main functions are: - 2.20V (STC706Y, 813Y, 708Y) • 200ms reset pulse width 1. Asserting reset output during power-µp, power- • Debounced TTL/CMOS-compatible manual- down and brownout conditions for µP system; 2. Detecting power failure or low-battery conditions reset input with a 1.25V threshold detector; • Independent watchdog timer 1.6sec time-out (not 3. Watchdog functions (not for STC708x). available for STC707/708/708T/708S/R/Z/Y) • Reset output signal: Applications - Active-low only (STC705/706/706T/S/R/Z/Y) - Active-high only (STC813L/M/T/S/R/706P) • Power-supply circuitry in µP systems - 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 STC 1 Ver1.0 Data Sheet STC705-706/706P-707-708-708T/S/R-813L µP 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 µP 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 RESET *706X (RESET *813X,706P) Vcc V RST PFI PFO 1.25V Figure 2. Block Diagram of STC708X / 707 Vcc 250uA RESET MR Reset Generator RESET Vcc VRST PFI PFO 1.25V STC 3 Ver1.0 Data Sheet STC705-706/706P-707-708-708T/S/R-813L µP 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 STC813L/M/T/S/R/706PESA STC813L/M/T/S/R/706PEPA 8-Pin SOIC/8-Pin PDIP STC708L/M/T/S/RESA STC708L/M/T/S/REPA 8-Pin SOIC/8-Pin PDIP MR 1 8 WDO MR 1 8 WDO MR 1 8 RESET V CC 2 7 RESET V CC 2 7 RESET V CC 2 7 RESET GND 3 6 WDI GND 3 6 WDI GND 3 6 NC PFI 4 5 PFO PFI 4 5 PFO PFI 4 5 PFO Top View Pin Description Table 1. Pin Description P in Na m e Typ e MR I Vcc Power Power Su p p ly GND Ground G r ou n d R efer en ce for all signals PFI I 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. PFO O 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. I 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. WDI NC 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 250µA pull-up current and be driven from a TTL or CMOS logic line as well as shorted to ground with a switch. 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. WDO O 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. RESET O T h e inver se of R E SE T: active high. Whenever RESET is high, RESET is low. RESET STC 4 Ver1.0 Data Sheet STC705-706/706P-707-708-708T/S/R-813L µP Supervisor Circuits -------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Functional Description Watchdog Timer 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. The watchdog circuit monitors the µP’s activity. If the µP 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. Reset Output Typically, WDO will be connected to the non-maskable interrupt input (NMI) of a µP. 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. 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. 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. 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 µPs, such as Intel’s 80C51, require an active-high reset pulse. 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 µP OUT Vcc Vcc RESET µP Supervisory Circuit PFI WDI WDO MR PFO STC 5 RESET I/O Line NMI Interrupt Ver1.0 Data Sheet STC705-706/706P-707-708-708T/S/R-813L µP Supervisor Circuits -------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Function Reference Table Table 2. Function Table of PT7A75xx Family Part No. STC Reset Threshold STC706L/705 4.63V STC813L STC708L/707 STC706M/706 STC813M Reset Active Low Nom. Reset Time Nom. Watch dog or High (ms), t RS Time (sec), t WD Power Fail Comp. Manual Reset Input 1.6 1.25V detector Yes LOW 200 4.63V HIGH 200 1.6 1.25V detector Yes 4.63V LOW, HIGH 200 unavailable 1.25V detector Yes 4.38V LOW 200 1.6 1.25V detector Yes 4.38V HIGH 200 1.6 1.25V detector Yes STC708M/708 4.38V LOW, HIGH 200 unavailable 1.25V detector Yes STC706T 3.08V LOW 200 1.6 1.25V detector Yes STC813T 3.08V HIGH 200 1.6 1.25V detector Yes STC708T 3.08V LOW, HIGH 200 unavailable 1.25V detector Yes STC706S 2.93V LOW 200 1.6 1.25V detector Yes STC813S 2.93V HIGH 200 1.6 1.25V detector Yes STC708S 2.93V LOW, HIGH 200 unavailable 1.25V detector Yes STC706R 2.63V LOW 200 1.6 1.25V detector Yes STC813R/706P 2.63V HIGH 200 1.6 1.25V detector Yes STC708R 2.63V LOW, HIGH 200 unavailable 1.25V detector Yes STC706Z 2.32V LOW 200 1.6 1.25V detector Yes STC813Z 2.32V HIGH 200 1.6 1.25V detector Yes STC708Z 2.32V LOW, HIGH 200 unavailable 1.25V detector Yes STC706Y 2.20V LOW 200 1.6 1.25V detector Yes STC813Y 2.20V HIGH 200 1.6 1.25V detector Yes STC708Y 2.20V LOW, HIGH 200 unavailable 1.25V detector Yes 6 Ver1.0 Data Sheet STC705-706/706P-707-708-708T/S/R-813L µP Supervisor Circuits -------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Mechanical Information Figure 7. 8-Pin SOIC STC 8 Ver1.0