SP691A_05 Datasheet, PDF (14/24 Pages) Sipex Corporation – Low Power Microprocessor Supervisory with Battery Switch-Over

VBATT ₁
2.8V
CEIN
13
12 ^CEOUT
4
GND
CLOAD
+2.0V
to
+5.5V
+5V
VBATT
R1
PFI
R2
VCC
PFO _{LOW BATT}
GND
Figure 22. Chip Enable Propagation Delay Test Circuit
Figure 23. Low-Battery Indicator Circuit
Chip-Enable Output
In the enabled mode, the impedance of CE
OUT
is equivalent to 65Ω in series with the source
driving CE_IN. In the disabled mode, the 65Ω
transmission gate is off and CE is actively
OUT
pulled to VOUT. This source turns off when the
transmission gate is enabled.
LOWLINE Output
LOWLINE is the buffered output pin of the
reset threshold comparator. Refer to Figure 16.
LOWLINE typically sinks 3.2mA at 0.1V. For
normal operation where V_CC is above the reset
threshold, LOWLINE is pulled to V_OUT.
Power-Fail Comparator
The power-fail comparator is an uncommitted
comparator that has no effect on the other
functions of the SP691A/693A/800L/800M
devices. Common uses include low battery
detection, as found in Figure 23, and early
power-fail detection when the unregulated power
is easily accessible as shown in Figure 17.
Power-Fail Input
The Power-Fail Input (PFI) has a guaranteed
input leakage of +25nA max over temperature.
The typical comparator delay is 25µs from VIL
to VOL (power failing), and 60µs from VIH to
VOH (power being restored). Connect this
input to ground if PFI is not used.
Power-Fail Output
The Power-Fail Output (PFO) goes low when
PFI goes below 1.25V. It sinks 3.2mA with a
saturation voltage of 0.1V. With PFI above
1.25V, PFO is actively pulled to VOUT. PFO
can be used to generate an NMI for the µP, as
shown in Figure 17.
Battery-Backup Mode
The SP691A/693A/800L/800M requires two
conditions to switch to battery-backup mode:
1) VCC must be below the reset threshold; 2)
VCC must be below VBATT. Table 2 lists the
status of the inputs and outputs in battery-
backup mode.
Battery-On Output
The Battery On Output (BATT ON) indicates
the status of the internal VCC/battery-switchover
comparator, which controls the internal VCC and
VBATT switches. For VCC greater that VBATT
(ignoring the small hysteresis effect), BATT ON
is a logic low. For V less than V , BATT
CC
BATT
ON is a logic high. Use BATT ON to indicate
battery-switchover status or to supply base drive
to an external pass transistor for higher-current
applications. Refer to Figure 17.
Date: 4/18/05
SP691A/693A/800L/800M Low Power Microprocessor Supervisor with Battery Switch-Over © Copyright 2005 Sipex Corporation
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