ASM690A / 692A
ASM802L / 802M
ASM805L
October 2003
rev 1.0
µP Power Supply Supervisor With Battery Backup Switch
General Description
Applications
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 battery-
backup switching to maintain control in power loss and brown-
out 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:
•
•
•
•
•
•
•
•
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
Typical Operating Circuit
Unregulated DC
Regulated +5V
V
V
CC
CC
0.1 µF
R
1
RESET
PFO
RESET
NMI
•
•
1.6 second watchdog timer to keep microprocessor
responsive
PFI
V
BATT
WDI
I/O LINE
GND
R
2
4.40V or 4.65V VCC threshold for microprocessor reset at
power-up and power-down
+
V
3.6 V
GND
OUT
_
Lithium
Battery
•
•
SPDT (Single-pole, Double-throw) PMOS switch connects
backup power to RAM if VCC fails
ASM690A
1.25V threshold detector for power loss or general purpose
voltage monitoring
CMOS
V
RAM
CC
These features are pin-compatible with the industry standard
power-supply supervisors. Short-circuit and thermal protection
have also been added. The AS690A / AS802L / AS805L
generate a reset pulse when the supply voltage drops below
4.65V and the AS692A / AS802M generate a reset below
4.40V. The ASM802L / ASM802M have power-fail accuracy to
± 2%. The ASM805L is the same as the ASM690A except that
RESET is provided instead of RESET.
GND
Block Diagram
1
8
Battery-Switchover Circuit
V
V
OUT
BATT
2
V
CC
7
Reset
RESET
(RESET)
Generator
+
-
|+
Features
1.25V
Watchdog
Timer
•
Two precision supply-voltage monitor options
•4.65V (AS690A / AS802L / AS805L)
•4.40V (AS692A / AS802M )
3.5V
+
-
|+
6
4
-
WDI
PFI
•
•
•
•
•
•
•
Battery-backup power switch on-chip
Watchdog timer: 1.6 second timeout
Power failure / low battery detection
Short circuit protection and thermal limiting
Small 8-pin SO package
|+
+
1.25V
|+
0.8V
5
-
PFO
+
ASM690A, ASM692A, ASM802L, ASM802M, (ASM805L)
GND
3
No external components
Specified over full temperature range
Alliance Semiconductor
2575 Augustine Drive . Santa Clara, CA 95054 . Tel: 408.855.4900 . Fax: 408.855.4999 . www.alsc.com
Notice: The information in this document is subject to change without notice