ASM690A

October 2003 rev 1.0 ASM690A / 692A ASM802L / 802M ASM805L µP Power Supply Supervisor With Battery Backup Switch Applications Embedded control systems Portable/Battery operated systems Intelligent instruments Wireless instruments Wireless communication systems PDAs and hand-held equipments µP / µC power supply monitoring Safety system General Description The AS690A / AS692A / AS802L / AS802M / AS805L offers complete single chip solutions for power supply monitoring and control battery functions in microprocessor systems. Each device implements four functions: Reset control, watchdog monitoring, battery-backup switching and power-failure monitoring. In addition to microprocessor reset under power-up and power-down conditions, these devices provide batterybackup switching to maintain control in power loss and brownout situations. Additional monitoring capabilities can provide an early warning of unregulated power supply loss before the voltage regulator drops out. The important features of these four functions are: Typical Operating Circuit Unregulated DC Regulated +5V VCC RESET PFI R2 VBATT PFO WDI VOUT RESET NMI VCC www.DataSheet4U.com R1 0.1 µF 1.6 second watchdog timer to keep microprocessor responsive 4.40V or 4.65V VCC threshold for microprocessor reset at power-up and power-down SPDT (Single-pole, Double-throw) PMOS switch connects backup power to RAM if VCC fails 1.25V threshold detector for power loss or general purpose voltage monitoring...