SP703 SIPEX [Sipex Corporation], SP703 Datasheet - Page 9

• Manufacturer Part Number: SP703
• Description: Low Power Microprocessor Supervisory with Battery Switch-Over
• Manufacturer: SIPEX [Sipex Corporation]

FEATURES
The SP703/704 devices provide four key func-
tions:
1. A battery backup switching 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 manual reset has been
pulled below 0.8V for at least 150ns.
4. A 1.25V threshold detector for power-fail
warning, low battery detection, or to monitor a
power supply other than +5V.
The SP703/704 devices differ only in their
supply voltage monitor level. The SP703
generates a reset when V
while the SP704 generates a reset below 4.4V.
The SP703/704 devices are ideally suited for
applications in automotive systems, intelligent
instruments, and battery-powered computers and
controllers. All designs into an environment
where it is critical to monitor the power supply
to the P and its related digital components will
find the SP703/704 ideal.
Figure 8. Typical Operating Circuit
SP703/704DS/07
CMOS
BUS
RAM
P
GND
V
CC
Pushbutton
GND
RESET
NMI
V
Regulated +5V
CC
Switch
RESET
0.1 F
PFO
MR
V
OUT
CC
drops below 4.65V
GND
V
CC
Unregulated
SP703/704 Low Power Microprocessor Supervisory
PFI
V
BATT
DC
Lithium
Battery
3.6V
R
R
1
2
9
THEORY OF OPERATION
Reset Output
The microprocessor's ( P's) reset input starts
the P in a known state. When the P is in an
unknown state, it should be held in reset. The
SP703/704 assert reset during power-up and
prevent code execution errors during power-
down or brownout conditions.
On power-up, once V
guaranteed to be a logic low. As V
RESET remains low. When V
reset threshold, RESET will remain low for
200ms, Figure 9. If a brownout condition
occurs and V
RESET is triggered. Each time RESET is trig-
gered, it stays low for the reset pulse width
interval. If a brownout condition interrupts a
previously initiated reset pulse, the reset pulse
continues for another 200ms. On power-down,
once V
guaranteed to be logic low until V
below 1V. RESET is also triggered by a
manual reset
CC
goes below the threshold, RESET is
CC
dips below the reset threshold,
CC
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reaches 1V, RESET is
CC
exceeds the
CC
CC
drops
rises,