MAX691A MAXIM [Maxim Integrated Products], MAX691A Datasheet - Page 11

• Manufacturer Part Number: MAX691A
• Description: Microprocessor Supervisory Circuits
• Manufacturer: MAXIM [Maxim Integrated Products]

Figure 6. CE Propagation Delay Test Circuit
Table 2. Input and Output Status in Battery-Backup
Mode
* V
mode.
PIN
10
11
12
13
14
15
16
CC
1
2
3
4
5
6
7
8
9
IMPEDANCE
OUTPUT
must be below the reset threshold to enter battery-backup
50
2.8V
LOWLINE
BATT ON
OSC SEL
CE OUT
OSC IN
VBATT
RESET
RESET
NAME
CE IN
V
WDO
GND
PFO
V
WDI
PFI
OUT
CC
______________________________________________________________________________________
Supply current is 1µA max.
V
internal PMOS switch.
Battery switchover comparator monitors
V
GND 0V, 0V reference for all signals.
Logic high. The open-circuit output is
equal to V
Logic low*
OSC IN is ignored.
OSC SEL is ignored.
The power-fail comparator remains
active in the battery-backup mode for
V
The power-fail comparator remains
active in the battery-backup mode for
V
age, PFO is forced low.
Watchdog is ignored.
Logic high. The open-circuit voltage is
equal to V
High impedance
Logic high. The open-circuit voltage is
equal to V
Logic low*
High impedance*
OUT
CC
CC
CC
VBATT
CE IN
for active switchover.
≥ VBATT - 1.2V typ.
≥ VBATT - 1.2V typ. Below this volt-
is connected to VBATT through an
MAX800M
MAX691A
MAX693A
MAX800L
GND
V
+5V
Microprocessor Supervisory Circuits
CC
OUT
OUT
OUT
CE OUT
.
.
.
STATUS
C
LOAD
The Power-Fail Output (PFO) goes low when PFI goes
below 1.25V. It typically sinks 3.2mA with a saturation
voltage of 0.1V. With PFI above 1.25V, PFO is actively
pulled to V
Two conditions are required to switch to battery-back-
up mode: 1) V
and 2) V
tus of the inputs and outputs in battery-backup mode.
The Battery On (BATT ON) output indicates the status
of the internal V
which controls the internal V
For V
teresis effect), BATT ON typically sinks 3.2mA at 0.1V
saturation voltage. In battery-backup mode, this termi-
nal sources approximately 10µA from V
ON to indicate battery-switchover status or to supply
base drive to an external pass transistor for higher-cur-
rent applications (see Typical Operating Circuit ).
The Input Supply Voltage (V
5V. V
large PMOS switch. The switch carries the entire cur-
rent load for currents less than 250mA. The parallel
diode carries any current in excess of 250mA. Both the
switch and the diode have impedances less than 1Ω
each. The maximum continuous current is 250mA, but
power-on transients may reach a maximum of 1A.
Figure 7. Low-Battery Indicator
2.0V to 5.5V
CC
CC
CC
greater than VBATT (ignoring the small hys-
connects to V
OUT
must be below VBATT. Table 2 lists the sta-
.
CC
CC
must be below the reset threshold,
/battery-switchover comparator,
VBATT
PFI
OUT
MAX800M
MAX691A
MAX693A
MAX800L
GND
Battery-Backup Mode
V
+5V
Input Supply Voltage
CC
CC
via a parallel diode and a
CC
) should be a regulated
Battery On Output
and VBATT switches.
PFO
Power-Fail Output
OUT
. Use BATT
LOW BATT
11