IMP690A , 692A , 802L/M, 805L
P
OWER
M
ANAGEMENT
碌P Power Supply Supervisor
with Battery Backup Switch
The IMP690A/IMP692A/IMP802L/IMP802M/IMP805L simplify power
supply monitoring and control in microprocessor systems. Each circuit
implements four functions: Reset control, watchdog monitoring, battery-
backup switching and power-failure monitoring. In addition to
microprocessor reset under powerup 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:
a) 1.6 second watchdog timer to keep microprocessor responsive
b)
c)
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
Key Features
x
Design improvement over Maxim
MAX690A/692A/802L/802M/805L
鈥?70% lower current than Maxim:
100碌A(chǔ) maximum
鈥?RESET Operation to 1.1V
x
Two precision supply-voltage monitor options
鈥?4.65V (IMP690A/802L/805L)
鈥?4.40V (IMP692A/802M)
x
Battery-backup power switch on-chip
x
Watchdog timer: 1.6 second timeout
x
Power failure/low battery detection
x
Short-circuit protection and thermal limiting
x
Small 8-pin SO package
x
No external components
x
Specified over full temperature range
d) 1.25V threshold detector for power loss or general purpose voltage
monitoring
While these features are pin鈥揷ompatible with the industry standard
power鈥搒upply supervisors offered by Maxim, the IMP devices are supe-
rior replacements and can reduce power requirements by 70 percent
when compared to Maxim MAX690/MAX692A/MAX802L/MAX802M/
MAX805L devices. Short-circuit and thermal protection have also
been added.
The IMP690A/IMP802L/IMP805L generate a reset pulse when the
supply voltage drops below 4.65V, and the IMP692A/IMP802M
generate a reset below 4.40V. The IMP802L/IMP802M have power鈥揻ail
accuracy to 鹵2%. The IMP805L is the same as the IMP690A except that
RESET is provided instead of錚?/div>
錚ワ％錚ワ％錚?/div>
錚?/div>
RESET.
Applications
x
Embedded control systems
x
Battery鈥搊perated systems
x
Intelligent instruments
x
Wireless communication systems
x
PDAs and handheld equipment
x
碌P/碌C
power supply monitoring
Block Diagrams
V
BATT
V
CC
+
Typical Application
1
7
V
OUT
RESET
(RESET)
Unregulated DC
Regulated +5V
V
CC
RESET
PFI
R
2
PFO
WDI
V
OUT
NMI
I/O LINE
GND
BUS
CMOS
V
CC
RAM
GND
690A_01.eps
8
2
Battery-Switchover
Circuit
Reset
Generator
+
R
1
0.1碌F
V
CC
RESET
1.25V
3.5V
6
WDI
+
+
+
+
Watchdog
Timer
+
鈥?/div>
3.6V
Lithium
Battery
V
BATT
GND
0.8V
4
PFI
1.25V
+
+
IMP690A
5
PFO
IMP690A, IMP692A, IMP802L, IMP802M,
IMP805L
( ) IMP805L
3
GND
690A_03.eps
IMP, Inc.
San Jose, CA
408-432-9100/www.impweb.com
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