MAX791 19-0075 Rev. 7 11/05 Microprocessor Supervisory Circuit General Description Features The MAX791 microprocessor (P) supervisory circuit Precision 4.65V Voltage Monitoring reduces the complexity and number of components need- 200ms Power-OK/Reset Time Delay ed to monitor power-supply and battery-control functions Independent Watchdog TimerPreset or Adjustable in P systems. The 50A supply current makes the 1A Standby Current MAX791 ideal for use in portable equipment, while the 6ns chip-enable propagation delay and 250mA output capa- Power Switching bility (25mA in battery-backup mode) make it suitable for 250mA Output in V Mode CC larger, higher-performance equipment. 25mA Output in Battery-Backup Mode The MAX791 comes in 16-pin DIP, TSSOP, and narrow SO On-Board Gating of Chip-Enable Signals packages and provides the following functions: Memory Write-Cycle Completion 6ns CE Gate Propagation Delay P reset. RESET output is asserted during power-up, power-down, and brownout conditions, and is guaran- MaxCap or SuperCap Compatible teed to be in the correct state for V down to 1V, CC Voltage Monitor for Power-Fail or Low-Battery Warning even with no battery in the circuit. Backup-Battery Monitor Manual-reset input. Guaranteed RESET Valid to V = 1V CC A 1.25V threshold detector provides for power-fail warning and low-battery detection, or monitors a Ordering Information power supply other than +5V. PART TEMP RANGE PIN-PACKAGE Two-stage power-fail warning. A separate low-line MAX791CPE 0C to +70C 16 Plastic DIP comparator compares V to a threshold 150mV CC above the reset threshold. MAX791CSE 0C to +70C 16 Narrow SO Backup-battery switchover for CMOS RAM, real-time MAX791C/D 0C to +70C Dice* clocks, Ps, or other low-power logic. MAX791CUE 0C to +70C 16 TSSOP Software monitoring of backup-battery voltage. MAX791EPE -40C to +85C 16 Plastic DIP A watchdog-fault output is asserted if the watchdog MAX791ESE -40C to +85C 16 Narrow SO input has not been toggled within either a preset or MAX791EJE -40C to +85C 16 CERDIP an adjustable timeout period. MAX791EUE -40C to +85C 16 TSSOP Write protection of CMOS RAM or EEPROM. MAX791MJE -55C to +125C 16 CERDIP Pulsed watchdog output to give advance warning of * Dice are specified at T = +25C. impending WDO assertion caused by watchdog timeout. A Devices in PDIP, SO and TSSOP packages are available in both Applications leaded and lead-free packaging. Specify lead free by adding the + symbol at the end of the part number when ordering. Computers Critical P Power Monitoring Lead free not available for CERDIP package. Controllers Intelligent Instruments Portable/Battery- Typical Operating Circuit Powered Equipment +5V Pin Configuration CMOS 0.1F 0.1F RAM TOP VIEW VBATT WDPO V BATT SWT 1 CC 16 0.47F* ON V OUT VBATT V OTHER SYSTEM OUT 2 RESET 15 RESET SOURCES CE OUT V WDO CC 3 14 GND MR 4 MAX791 CE IN 13 ADDRESS CE IN +12V DECODE BATT ON 5 CE OUT 12 A0A15 MAX791 PFI P PFO 6 WDI 11 +12V SUPPLY WDI I/O PFI PFO 7 10 LOWLINE LOWLINE NMI FAILURE GND SWT 8 9 MR RESET RESET INT WDO DIP/SO/TSSOP * MaxCap MaxCap is a registered trademark of Cesiwid Inc. SuperCap is a registered trademark of Baknor Industries. Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct at 1-888-629-4642, or visit Maxims website at www.maxim-ic.com.Microprocessor Supervisory Circuit ABSOLUTE MAXIMUM RATINGS Input Voltage (with respect to GND) Continuous Power Dissipation (T = +70C) A V .......................................................................-0.3V to +6V Plastic DIP (derate 10.53mW/C above +70C) ..........842mW CC VBATT..................................................................-0.3V to + 6V Narrow SO (derate 8.70mW/C above +70C) ............696mW All Other Inputs.....................................-0.3V to (V + 0.3V) CERDIP (derate 10.00mW/C above +70C)...............800mW OUT Input Current TSSOP (derate 6.70mW/C above +70C) ..................533mW V Peak ..........................................................................1.0A Operating Temperature Ranges CC V Continuous ............................................................250mA MAX791C ......................................................OC to +70C CC VBATT Peak ..................................................................250mA MAX791E ....................................................-40C to +85C VBATT Continuous..........................................................25mA MAX791MJE ..................................................-55C to +125C GND, BATT ON.............................................................100mA Storage Temperature Range .............................-65C to +160C All Other Outputs ............................................................25mA Lead Temperature (soldering, 10s) .................................+300C 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 = 4.75V to 5.5V, VBATT = 2.8V, T = T to T , unless otherwise noted.) CC A MIN MAX PARAMETER CONDITIONS MIN TYP MAX UNITS Operating Voltage Range 0 5.5 V V , VBATT (Note 1) CC I = 25mA V - 0.05 V - 0.02 OUT CC CC V = 4.5V MAX791C/E V - 0.3 V - 0.2 V in Normal CC CC CC OUT I = 250mA V OUT Operating Mode MAX791M V - 0.40 CC V = 3V, VBATT = 2.8V, I = 100mA V - 0.2 V - 0.12 CC OUT CC CC MAX791C/E 0.8 1.2 V = 4.5V CC V -to-V On-Resistance MAX791M 0.8 1.6 CC OUT V = 3V 1.2 2.0 CC VBATT = 4.5V, I = 20mA VBATT - 0.3 OUT V in Battery-Backup Mode VBATT = 2.8V, I = 10mA VBATT - 0.25 V OUT OUT VBATT = 2.0V, I = 5mA VBATT - 0.15 OUT VBATT = 4.5V 815 VBATT-to-V On-Resistance VBATT = 2.8V 13 25 OUT VBATT = 2.0V 17 30 Supply Current in Normal V > VBATT - 1V 50 150 A CC Operating Mode (excludes I ) OUT T = +25C 0.04 1 Supply Current in Battery-Backup V < VBATT - 1.2V, A CC A Mode (excludes I ) (Note 2) VBATT = 2.8V OUT T = T to T 5 A MIN MAX T = +25C -0.1 0.02 A VBATT Standby Current VBATT + 0.2V V A CC (Note 3) T = T to T -1.0 0.02 A MIN MAX Power up VBATT + 0.03 Battery-Switchover Threshold V Power down VBATT - 0.03 Battery-Switchover Hysteresis 60 mV Low-Battery Detector Threshold 2 V 2 MAX791