sp691a Exar Corporation, sp691a Datasheet - Page 14

• Manufacturer Part Number: sp691a
• Description: Low Power Microprocessor Supervisory With Battery Switch-over
• Manufacturer: Exar Corporation

Figure 22. Chip Enable Propagation Delay Test Circuit
Chip-Enable Output
In the enabled mode, the impedance of CE
is equivalent to 65Ω in series with the source
driving CE
transmission gate is off and CE
pulled to V
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
threshold, LOWLINE is pulled to V
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 V
to V
V
input to ground if PFI is not used.
Date: 4/18/05
OH
2.8V
OL
(power being restored). Connect this
(power failing), and 60µs from V
V
OUT
BATT
IN
. In the disabled mode, the 65Ω
SP691A/693A/800L/800M Low Power Microprocessor Supervisor with Battery Switch-Over © Copyright 2005 Sipex Corporation
1
. This source turns off when the
4
GND
13
12
CC
CE
CE
is above the reset
IN
OUT
OUT
OUT
is actively
C
.
LOAD
IH
OUT
IL
to
14
Figure 23. Low-Battery Indicator Circuit
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 V
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) V
V
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 V
comparator, which controls the internal V
V
(ignoring the small hysteresis effect), BATT ON
is a logic low. For V
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.
BATT
+2.0V
+5.5V
CC
to
CC
must be below V
switches. For V
must be below the reset threshold; 2)
R
R
V
1
2
PFI
BATT
+5V
CC
V
GND
BATT
CC
CC
less than V
CC
PFO
greater that V
/battery-switchover
. Table 2 lists the
LOW BATT
BATT
OUT
, BATT
. PFO
CC
BATT
and