SP690SEN-L Datasheet, PDF (12/20 Pages) Sipex Corporation – 3.0V/3.3V Low Power Microprocessor Supervisory with Battery Switch-Over

FEATURES
The SP690T/S/R, SP802T/S/R, SP804T/S/R
and SP805T/S/R devices provide four key
functions:
1. A battery backup switch for CMOS RAM,
CMOS microprocessors, or other logic.
2. A reset output during power-up, power-down
and brownout conditions.
3. A reset pulse if the optional watchdog timer
has not been toggled within a specified time.
4. A 1.25V threshold detector for power-fail
warning, low battery detection, or to monitor a
power supply other than 3.3V or 3.0V.
The SP690T/S/R, SP802T/S/R, SP804T/S/R
and SP805T/S/R devices differ in their reset-
voltage threshold levels and are ideally suited
for applications in automotive systems, intelligent
instruments, and battery-powered computers and
controllers. The series is a solid match for
designs where it is critical to monitor the
power supply to the µP and it’s related digital
components.
Regulated +3.3V or +3.0V
Unregulated
VCC
0.1µF
DC
µP ^RESET
NMI
I/O LINE
GND
VCC
pin 7*
PFO
WDI
SP690T/S/R
SP802T/S/R
SP804T/S/R
SP805T/S/R
VOUT
R1
PFI
R2
VBATTERY
BUS
GND
CMOS VCC
RAM
GND
0.1µF
3.6V
Lithium
Battery
*^{RESET for the SP690T/S/R and the SP802T/S/R}
RESET for the SP804T/S/R and the SP805T/S/R
Figure 20. Typical Operating Circuit
THEORY OF OPERATION
The SP690T/S/R, SP802T/S/R, SP804T/S/R
and SP805T/S/R devices are microprocessor
(µP) supervisory circuits that monitor the power
supplied to digital circuits such as microproces-
sors, microcontrollers, or memory. The series is
an ideal solution for portable, battery-powered
equipment that requires power supply monitoring.
Implementing this series will reduce the
number of components and overall complexity.
The watchdog functions of this product family
will continuously oversee the operational status
of a system.
These µP supervisory circuits are not short-
circuit protected. Shorting V_OUT to ground -
excluding power-up transients such as charging
a decoupling capacitor - may potentially damage
these devices. Decouple both V_CC and V_BATTERY
pins to ground by placing 0.1µF capacitors as
close to the device as possible. The operational
features and benefits of the SP690T/S/R,
SP802T/S/R, SP804T/S/R and SP805T/S/R
devices are described in more detail below.
Reset Output
The microprocessor's (µP's) reset input starts
the µP in a known state. When the µP is in an
unknown state, it should be held in reset. The
SP690T/S/R, SP802T/S/R, SP804T/S/R and
SP805T/S/R devices assert reset during
power-up and prevent code execution errors
during power-down or brownout conditions.
RESET is guaranteed to be a logic LOW for 0V
< V_CC < V_RST, provided that V_BATTERY is greater
than 1V. Without a backup battery, RESET is
guaranteed valid for V_CC > 1V. Once V_CC
exceeds the reset threshold, an internal timer
keeps RESET low for the reset timeout period.
After this period, RESET goes HIGH, as seen in
Figure 19.
If a brownout condition occurs and V_CC dips
below the reset threshold, RESET goes LOW.
Each time RESET is triggered, it stays low for
the reset timeout period. Any time V_CC goes
below the reset threshold, the internal timer
restarts.
SP690T/S/R JAN 30-06 SP690T/S/R, 802/T/S/R, 804T/S/R, 805T/S/R Low Power Microprocessor Supervisory
12
© 2006 Sipex Corporation