IMP690A Datasheet, PDF (1/10 Pages) IMP, Inc – μP POWER SUPPLY SUPERVISOR WITH BATTERY BACKUP SWITCH

IMP690A, 692A, 802L/M, 805L
POWER MANAGEMENT
µP 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) 4.40V or 4.65V V_CC threshold for microprocessor reset at power-up
and power-down
c) SPDT (single-pole, double-throw) PMOS switch connects backup
power to RAM if V_CC fails
d) 1.25V threshold detector for power loss or general purpose voltage
monitoring
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.
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RESET.
Block Diagrams
Key Features
x Design improvement over Maxim
MAX690A/692A/802L/802M/805L
— 70% lower current than Maxim:
100µA maximum
— RESET Operation to 1.1V
x Two precision supply-voltage monitor options
— 4.65V (IMP690A/802L/805L)
— 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
Applications
x Embedded control systems
x Battery–operated systems
x Intelligent instruments
x Wireless communication systems
x PDAs and handheld equipment
x µP/µC power supply monitoring
Typical Application
8
V_BATT
2
V_CC
Battery-Switchover
Circuit
Reset
Generator
+
1
V_OUT
7 _RESET
(RESET)
1.25V
3.5V
+
Watchdog
Timer
6
WDI
+ _1.25V
0.8V
5
4
+
PFI
IMP690A, IMP692A, IMP802L, IMP802M,
PFO
IMP805L
( ) IMP805L
3 _GND
690A_03.eps
IMP, Inc.
San Jose, CA
Unregulated DC
Regulated +5V
R₁
R_{2 +}
–
0.1µF
V_CC
RESET
PFI PFO
3.6V
Lithium
Battery
V_BATT
GND
WDI
V_OUT
IMP690A
V_CC
RESET
NMI
I/O LINE
GND
CMOS
V_CC ^RAM
GND
690A_01.eps
408-432-9100/www.impweb.com