MAX792/MAX820 19-0147 Rev. 4 11/05 Microprocessor and Nonvolatile Memory Supervisory Circuits General Description Features The MAX792/MAX820 microprocessor (P) supervisory Manual-Reset Input circuits provide the most functions for power-supply 200ms Power-OK/Reset Time Delay and watchdog monitoring in systems without battery Independent Watchdog TimerPreset or Adjustable backup. Built-in features include the following: On-Board Gating of Chip-Enable Signals P reset: Assertion of RESET and RESET outputs during power-up, power-down, and brownout conditions. Memory Write-Cycle Completion RESET is guaranteed valid for V down to 1V. CC 10ns (max) Chip-Enable Gate Propagation Delay Manual-reset input. Voltage Monitor for Overvoltage Warning Two-stage power-fail warning: A separate low-line 2% Reset and Low-Line Threshold Accuracy comparator compares V to a preset threshold CC (MAX820, external programming mode) 120mV above the reset threshold the low-line and Ordering Information reset thresholds can be programmed externally. Watchdog fault output: Assertion of WDO if the watchdog PART** TEMP. RANGE PIN-PACKAGE input is not toggled within a preset timeout MAX792 CPE 0C to +70C 16 Plastic DIP period. MAX792 CSE 0C to +70C 16 Narrow SO Pulsed watchdog output: Advance warning of MAX792 C/D 0C to +70C Dice* impending WDO assertion from watchdog timeout that Ordering Information continued at end of data sheet. causes hardware shutdown. * Dice are tested at T = +25C, DC parameters only. A **These parts offer a choice of five different reset threshold voltages. Write protection of CMOS RAM, EEPROM, or other Select the letter corresponding to the desired nominal reset threshold memory devices. voltage and insert it into the blank to complete the part number. The MAX792 and MAX820 are identical, except the Devices in PDIP, SO and MAX packages are available in both lead- ed and lead-free packaging. Specify lead free by adding the + sym- MAX820 guarantees higher low-line and reset threshold bol at the end of the part number when ordering. Lead free not avail- accuracy (2%). able for CERDIP package. Applications SUFFIX RESET THRESHOLD (V) Computers L 4.62 M 4.37 Controllers T 3.06 S 2.91 Intelligent Instruments R 2.61 Critical P Power Monitoring Typical Operating Circuit V CC 0.1F 3 V V CC CC 13 CE OUT 4 RESET IN/INT P MAX792 RAM 14 5 ADDRESS LLIN/ CE IN A0-A15 DECODER REFOUT 6 OVO 10 LOW LINE NMI 1 7 RESET OVI RESET 8 9 MR SWT GND GND 12 Maxim Integrated Products 1 For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800. For small orders, phone 1-800-835-8769.Microprocessor and Nonvolatile Memory Supervisory Circuits ABSOLUTE MAXIMUM RATINGS Input Voltage (with respect to GND) Operating Temperature Ranges: V .......................................................................-0.3V to +6V MAX792 C /MAX820 C ...............................0C to +70C CC All Other Inputs.......................................-0.3V to (V + 0.3V) MAX792 E /MAX820 E .............................-40C to +85C CC Input Current MAX792 MJE /MAX820 MJE .................-55C to +125C GND ................................................................................25mA Storage Temperature Range .............................-65C to +160C All Other Outputs ............................................................25mA Lead Temperature (soldering, 10s) .................................+300C Continuous Power Dissipation (T = +70C) A Plastic DIP (derate 10.53mW/C above +70C) ..........842mW Narrow SO (derate 9.52mW/C above +70C) ............762mW CERDIP (derate 10.00mW/C above +70C)...............800mW Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (V = 2.75V to 5.5V, T = T to T , unless otherwise noted.) CC A MIN MAX PARAMETER CONDITIONS MIN TYP MAX UNITS Operating Voltage Range 2.75 V (Note 1) Supply Current 70 150 A RESET COMPARATOR MAX792L, MAX820L 4.50 4.62 4.75 MAX792M, MAX820M 4.25 4.37 4.50 MAX792R, MAX820R 2.55 2.61 2.70 MAX792S, MAX820S 2.85 2.91 3.00 Reset Threshold Voltage MAX792T, MAX820T 3.00 3.06 3.15 Internal Threshold Mode V MAX820L, T = +25C, V falling 4.55 4.70 A CC (V ) TH MAX820M, T = +25C, V falling 4.30 4.45 A CC MAX820R, T = +25C, V falling 2.55 2.66 A CC MAX820S, T = +25C, V falling 2.85 2.96 A CC MAX820T, T = +25C, V falling 3.00 3.11 CC A MAX792, V = 5V or V = 3V 1.25 1.30 1.35 Reset Threshold Voltage CC CC V External Threshold Mode (V ) TH MAX820, V = 5V or V = 3V 1.274 1.30 1.326 CC CC RESET IN/INT Mode Threshold Internal threshold mode 60 mV (Note 2) RESET IN/INT Leakage Current 0.01 25 nA Reset Threshold Hysteresis 0.016 x V V TH Reset Comparator Delay V falling 70 s CC Reset Active Timeout Period V rising 140 200 280 ms CC I = 50A, V = 1V, V falling 0.01 0.3 SINK CC CC I = 1.6mA 0.1 0.4 SINK RESET Output Voltage V I = 1mA V - 1 SOURCE CC I = 100A V - 0.5 SOURCE CC I = 1.6mA 0.1 0.4 SINK RESET Output Voltage I = 1mA V - 1 V SOURCE CC I = 100A V - 0.5 SOURCE CC 2 MAX792/MAX820