POWER MANAGEMENT.V µp P Power P Supply Monitor or and Reset R Circuit Selectable Trip-PT -Point TolerT olerance and Watchdog hdog PerP eriodiod Push-Button ResetR Push-Pull Reset R Outputs The IMP82 microprocessor supervisor can halt and restart a hungup or stalled microprocessor, restart a microprocessor after a power failure, and debounce a manual push-button microprocessor reset switch. The IMP82 features over 0% lower supply current than the pin compatible allas Semiconductor S82. Precision temperature compensated reference and comparator circuits monitor the.v, input voltage. uring power-up or when the power supply falls outside selectable tolerance limits, both and become active. When rises above the threshold voltage, the reset signals remain active for an additional 20ms minimum, allowing the power supply and system microprocessor to stabilize. The trip point tolerance signal,, selects the trip level tolerance to be either 0- or 20-percent. and outputs are push-pull. A debounced manual reset input,, activates the reset outputs for a minimum period of 20ms. Block iagram Key Features Pin compatible with the allas Semiconductor S82 Over 0% lower supply current.v supply monitor Push-pull output Selectable watchdog period ebounce manual push-button reset input Precision temperature-compensated voltage reference and comparator Power-up, power-down and brownout detection 20ms minimum reset time Active LOW and HIGH reset signal Selectable trip point tolerance: 0% or 20% Low-cost 8-pin IP/SO and 8-pin MicroSO packages Wide operating temperature 0 C to +8 C Also included is a watchdog timer to stop and restart a microprocessor that is hung-up. Three watchdog timeout periods are selectable: 0ms, 0ms and,200ms. If the input is not strobed LOW before the time-out period expires, a reset is issued. evices are available in 8-pin IP, 8-pin SO and compact 8-pin MicroSO packages. 8 IMP82 0%/20% Tolerance Selection + Reference 0kW Push Button ebounce 2 Watchdog Timebase Selection 7 Watchdog Transition etector Reset & Watchdog Timer 82_02.eps
Pin Configuration IP/SO/MicroSO 8 2 IMP82 7 82_0.eps Pin escriptions Pin Number 8-Pin Package Name Function ebounced manual pushbutton reset input 2 Watchdog time delay selection. (t = 0ms for =, t = 0ms for = Open, and t =200ms for = ) Selects 0% ( connected to ) or 20% ( connected to ) trip point tolerance Ground Active HIGH reset output. is active:. If falls below the reset voltage trip point. 2. If is LOW.. If is not strobed LOW before the timeout period set by expires.. uring power-up. Active LOW reset output. (See ) 7 Strobe Input 8 V power Ordering Information Part Number IMP82 IMP82S IMP82SEMA Package Operating Temperature Range imum Supply C urrent ( µ A) Voltage Monitoring Application 8 -IP 0 C to 8 C 20.V 8 -SO 0 C to 8 C 20.V 8 -MicroSO 0 C to 8 C 20.V 82_t0.eps 2
Absolute imum Ratings Voltage on........................ 0.V to 7V Voltage on,..................... 0.V to + 0.V Voltage on,,........ 0.V to + 0.V Operating Temperature Range........... 0 C to 8 C Soldering Temperature.................. 20 C for 0 seconds Storage Temperature................... C to 2 C Voltages measured with respect to ground. These are stress ratings only and functional operation is not implied. Electrical Characteristics Unless otherwise stated,.2v.v and over the operating temperature range of 0 C to +8 C. All voltages are referenced to ground. Parameter Symbol Conditions Typ Units Supply Voltage ( ).0. V and Input High Level V IH 2.7V 2 + 0.V V and Input High Level V IH < 2.7V - 0.V V and Input Low Level V IL 0. 0. V Trip Point ( = ) TP 2.80 2.88 2.97 V Trip Point ( = ) TP 2.7 2. 2. V Watchdog Time-Out Period t = 2. 0 20 ms Watchdog Time-Out Period t = 00 200 2000 ms Watchdog Time-Out Period t floating 20 0 000 ms Output Voltage V OH I = 00µA, < 2.7V - 0.V - 0.V V Output Current I OH Output = 2.V, 2.7V 0 µa Output Current I OL Output = 0.V, 2.7V 0 ma Input Leakage I IL.0.0 µa Low Level V OL 0. V Internal Pull-Up Resistor pin 0 kω Operating Current I CC Outputs open..v 20 µa and all inputs at or Input Capacitance C IN pf Output Capacitance C OUT 7 pf Manual Reset t PB = V IL 20 ms imum Low Time Reset Active Time t R 20 0 000 ms Pulse Width t Must not exceed t R minimum. 20 ns Watchdog cannot be disabled. Fail etect to t RP Pulses < 2µs at TP 8 µs or minimum will not cause reset. Slew Rate t F 20 µs Stable LOW to t PLY 20 ms and Active etect to or t RPU t rise = µs 20 0 000 ms Inactive Slew Rate t R 0 ns
Application Information Supply Voltage Monitor The IMP82 monitors the microprocessor or microcontroller power supply and issues reset signals, both active HIGH and active LOW, that halt processor operation whenever the power supply voltage levels are outside a predetermined tolerance. Tolerance levels are set with the pin. and signals are generated at the last moment of a valid signal. On power-up, both reset signals are active for a minimum of 20ms after the supply has returned to intolerance level. This allows the power supply and monitored processor to stabilize before instruction execution is allowed to begin. Trip Point Tolerance Selection With connected to, and become active whenever falls below 2.V. and become active when falls below 2.98V if is connected to ground. After has risen above the trip point set by, and remain active for a minimum time period of 20ms. On power-down, once falls below the reset threshold stays LOW and is guaranteed to be 0.V or less until drops below.2v. The active HIGH reset signal is valid down to a level of.2v also. Tolerance Select Tolerance TRIP Point Voltage (V) Nominal = VC C 20% 2.7 2. 2. T OL = 0% 2.80 2.88 2.97 Manual Reset Operation Push-button switch input,, allows the user to override the internal trip point detection circuits and issue reset signals. The pushbutton input is debounced and is pulled HIGH through an internal 0kΩ resistor. When is held LOW for the minimum time t PB, both resets become active and remain active for a minimum time period of 20ms after returns HIGH. 82 t02.eps TP(MIN) t R TP(MAX) TP The debounced input is guaranteed to recognize pulses greater than 20ms. No external pull-up resistor is required, since is pulled HIGH by an internal 0kΩ resistor. The can be driven from a TTL or CMOS logic line or shorted to ground with a mechanical switch. t RPU t PB V OH t PLY V IH V IL V OL t R Figure. Timing iagram: Power Up 82_0.eps V OH V OL 82_07.eps t F Figure. Timing iagram: Pushbutton Reset TP(MAX) TP TP(MIN) IMP82 Supply Voltage 8 t RP 2 7 µp V OH V OL 82_0.eps Figure 2. Timing iagram: Power own 82_0.eps Figure. Application Circuit: Pushbutton Reset
Application Information Watchdog Timer and Input A watchdog timer stops and restarts a microprocessor that is hung-up. Through the time delay input,, three watchdog time-out periods are selectable: 0ms, 0ms and,200ms. If the strobe input,, is not strobed LOW prior to timeout, reset signals become active. On power-up or after the supply voltage returns to an in-tolerance condition, the reset signal remains active for 20ms minimum, allowing the power supply and system microprocessor to stabilize. Pulses as short as 20ns can be detected. t R Valid Strobe t t () Valid Strobe t () Invalid Strobe A HIGH-to-LOW signal transition must be regularly issued no later than the minimum time-out period defined by the state of the signal. This guarantees the watchdog timer does not time-out. Timeouts periods of approximately 0ms, 0ms or,200ms are selected through the pin. Voltage Level Watchdog Time-Out Period (ms) Nominal 2. 0 20 Floating 20 0 000 00 200 2000 82_t0.eps The watchdog timer can not be disabled. It must be strobed with a high-to-low transition to avoid a watchdog timeout and reset. 82_08.eps Note: is ignored whenever a reset is active. Figure. Timing iagram: Strobe Input Supply Voltage IMP82 8 MREQ 2 7 mp Address Bus ecoder 82_0.eps Figure. Application Circuit: Watchdog Timer
Package imensions e e b MicroSO (8-Pin) SO (8-Pin) 0 8 L E H C A B a E E Plastic IP (8-Pin) E E + C A 0.0mm 0.00in MicroSO (8-Pin).eps L SO (8-Pin).eps Inches MicroSO (8-Pin)* Millimeters A 0.0.0 0.0020 0.009 0.00 0. 0.029 0.07 0.7 0.9 b 0.0098 0.07 0.2 0.0 C 0.00 0.009 0. 0.2 0.2 0.220 2.90.0 e 0.02 BSC 0. BSC E 0.9 BSC.90 BSC E 0.2 0.220 2.90.0 L 0.07 0.027 0.0 0.70 a 0 0 SO (8-Pin)** A 0.0 0.09..7 0.00 0.00 0.0 0.2 B 0.0 0.020 0. 0. C 0.007 0.00 0.9 0.2 e 0.00.27 E 0.0 0.7.80.00 H 0.228 0.2.80.20 L 0.0 0.00 0.0.27 0.89 0.97.80 2.00 Plastic IP (8-Pin)*** A 0.20. 0.0 0.8 0. 0.9 2.92.9 b 0.0 0.022 0. 0. b2 0.0 0.070..78 b 0.00 0.0 0.80. 0. 0.00 9.02 0. 0.00 0. E 0.00 0.2 7.2 8.2 E 0.20 0.280.0 7. e 0.00 2. ea 0.00 7.2 e B 0.0 0.92 e C 0.00 L 0. 0.0 2.92.8 *** JEEC rawing MO-87AA *** JEEC rawing MS-2AA *** JEEC rawing MS-00BA 82_t0.at A L 0 e b2 b C ea eb Plastic IP (8-Pin)a.eps
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