ASM690 Datasheet, PDF (1/13 Pages) Alliance Semiconductor Corporation – UP Power Supply Supervisor With Battery Backup Switch

October 2003
ASM690A / 692A
ASM802L / 802M
ASM805L
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:
• 1.6 second watchdog timer to keep microprocessor
responsive
• 4.40V or 4.65V V_CC threshold for microprocessor reset at
power-up and power-down
• SPDT (Single-pole, Double-throw) PMOS switch connects
backup power to RAM if V_CC fails
• 1.25V threshold detector for power loss or general purpose
voltage monitoring
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.
Features
• Two precision supply-voltage monitor options
•4.65V (AS690A / AS802L / AS805L)
•4.40V (AS692A / AS802M )
• 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
• No external components
• Specified over full temperature range
• 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
R₁
0.1 µF
V_CC
RESET
PFI
PFO
R₂
V_BATT
WDI
+_{_}
3.6 V
Lithium
Battery
GND
V_OUT
ASM690A
V_CC
RESET
NMI
I/O LINE
GND
CMOS
V_CC RAM
GND
Block Diagram
8
V_BATT
Battery-Switchover Circuit
1
V_OUT
2
V_CC
6
WDI
4
PFI
+
|+
-
1.25V
3.5V
|+
+
-
Reset
Generator
Watchdog
Timer
-
|+
+
0.8V
1.25V
|+
-
+
ASM690A, ASM692A, ASM802L, ASM802M, (ASM805L)
7
RESET
(RESET)
5
PFO
3 GND
Alliance Semiconductor
2575 Augustine Drive . Santa Clara, CA 95054 . Tel: [phone] . Fax: [phone] . www.alsc.com
Notice: The information in this document is subject to change without notice