Date: 11/29/04

SP690A/692A Low Power Microprocessor Supervisory with Battery Switch-Over

© Copyright 2004 Sipex Corporation

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Using a High Capacity Capacitor

as a Backup Power Source

allowing use of a capacitor and a simple charging

circuit as a backup source (see Figure 16).

Leakage current through the capacitor charging

diode and the SP690A/SP802L/SP805L internal

power diode eventually discharges the capacitor

above the reset threshold and power is lost at

SP690A/SP802L/SP805L then switches to

battery-backup mode.

Figure 15. Allowable BACKUP-BATTERY Voltages

Figure 14. Input and Output Status in Battery-Backup Mode.

To enter the Battery-Backup mode, V

Reset threshold and less than V

Figure 16. Backup Power Source Using High Capacity

Capacitor with SP690A/802L/805L and a +5V

±5% Supply

Figure 17. Backup Power Source Using High Capacity

Capacitor with SP692A/802M/805M and a +5V

±10% Supply

+5V

GND

RESET

CONNECT TO

STATIC RAM

TO µP

0.1F

CONNECT

(RESET)*

*( ) SP805L only

+5V

GND

RESET

CONNECT TO

STATIC RAM

TO µP

100KΩ

0.1F

CONNECT

(RESET)*

*( ) SP805M only

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