IMP690A, 692A, 802L/M, 805L
P
OWER
M
ANAGEMENT
Key Features
µP Power Supply Supervisor
with Battery Backup Switch
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Design improvement over Maxim
MAX690A/692A/802L/802M/805L
— 70% lower current than Maxim:
100µA maximum
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:
— RESET Operation to 1.1V
Two precision supply-voltage monitor options
— 4.65V (IMP690A/802L/805L)
— 4.40V (IMP692A/802M)
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
◆
◆
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◆
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a) 1.6 second watchdog timer to keep microprocessor responsive
b) 4.40V or 4.65V VCC threshold for microprocessor reset at power-up
and power-down
No external components
Specified over full temperature range
c) SPDT (single-pole, double-throw) PMOS switch connects backup
power to RAM if VCC fails
d) 1.25V threshold detector for power loss or general purpose voltage
monitoring
Applications
While these features are pin–compatible with the industry standard
power–supply 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.
◆ Embedded control systems
◆ Battery–operated systems
◆ Intelligent instruments
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–fail
accuracy to ±2%. The IMP805L is the same as the IMP690A except that
RESET is provided instead of RESET.
◆ Wireless communication systems
◆ PDAs and handheld equipment
◆ µP/µC power supply monitoring
Block Diagrams
Typical Application
8
2
1
7
Battery-Switchover
Circuit
VBATT
VCC
Unregulated DC
Regulated +5V
VOUT
Reset
Generator
RESET
(RESET)
VCC
RESET
NMI
VCC
0.1µF
R1
+
RESET
PFO
PFI
Watchdog
Timer
1.25V
I/O LINE
GND
VBATT WDI
VOUT
GND
R2
3.5V
+
–
3.6V
Lithium
Battery
+
6
4
WDI
PFI
IMP690A
+
1.25V
+
CMOS
RAM
5
0.8V
VCC
PFO
GND
IMP690A, IMP692A, IMP802L, IMP802M,
IMP805L
690A_01.eps
3
690A_03.eps
( ) IMP805L
GND
IMP, Inc.
San Jose, CA
408-432-9100/www.impweb.com
IMP [ IMP, INC ]
