MAX791

Precision 4.65V Voltage Monitoring
200ms Power-OK/Reset Time Delay
Independent Watchdog Timer-Preset or Adjustable
1A Standby Current
Power Switching 250mA Output in VCC Mode 25mA Output in Battery-Backup Mode
On-Board Gating of Chip-Enable Signals Memory Write-Cycle Completion 6ns CE Gate Propagation Delay
MaxCap^TMor SuperCap^TM Compatible
Voltage Monitor for Power-Fail or Low-Battery Warning
Backup-Battery Monitor
Guaranteed RESET  Valid to V_CC = 1V

Computers                                    Critical P Power Monitoring
Controllers                                            Intelligent Instruments
Portable/Battery-Powered Equipment

Input Voltage (with respect to GND)
VCC.............................................................................................-0.3V to +6V
VBATT.........................................................................................-0.3V to + 6V
All Other Inputs...........................................................-0.3V to (VOUT + 0.3V)
Input Current
VCC Peak ................................................................................................1.0A
VCC Continuous ..................................................................................250mA
VBATT Peak ..........................................................................................250mA
VBATT Continuous...................................................................................25mA
GND, BATT ON.......................................................................................100mA
All Other Outputs ...................................................................................25mA
Continuous Power Dissipation (TA = +70°C)
Plastic DIP (derate 10.53mW/°C above +70°C) ...............................842mW
Narrow SO (derate 8.70mW/°C above +70°C) .................................696mW
CERDIP (derate 10.00mW/°C above +70°C).....................................800mW
Operating Temperature Ranges
MAX791C_ _ ............................................................................O°C to +70°C
MAX791E_ _ ..........................................................................-40°C to +85°C
MAX791MJE .........................................................................-55°C to +125°C
Storage Temperature Range ...............................................-65°C to +160°C
Lead Temperature (soldering, 10sec) .................................................+300°C

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.

The MAX791 microprocessor (P) supervisory circuit reduces the complexity and number of components needed to monitor power-supply and battery-control functions in P systems. The 50A supply current makes the MAX791 ideal for use in portable equipment, while the 6ns chip-enable propagation delay and 250mA output capability (25mA in battery-backup mode) make it suitable for larger, higher-performance equipment. The MAX791 comes in 16-pin DIP and narrow SO packages and provides the following functions:

1) P reset-RESET  output is asserted during power-up, power-down, and brownout conditions, and is guaranteed to be in the correct state for VCC down to 1V, even with no battery in the circuit.

2)Manual-reset input.

3) A 1.25V threshold detector provides for power-fail warning and low-battery detection, or monitors a power supply other than +5V.

4)Two-stage power-fail warning-a separate low-line comparator compares VCC to a threshold 150mV above the reset threshold.

5) Backup-battery switchover for CMOS RAM, real-time clocks, Ps, or other low-power logic.

6)Software monitoring of backup-battery voltage.

7)A watchdog-fault output is asserted if the watchdog input has not been toggled within either a preset or an adjustable timeout period.

8)Write protection of CMOS RAM or EEPROM.

9)Pulsed watchdog output, to give advance warning of impending WDO assertion caused by watchdog timeout.