ADM8693ARN Analog Devices Inc, ADM8693ARN Datasheet - Page 14

• Manufacturer Part Number: ADM8693ARN
• Description: IMPROVED ADM693 I.C.
• Manufacturer: Analog Devices Inc
• Type: Battery Backup Circuitr

Specifications of ADM8693ARN

• Rohs Compliant: NO
• Rohs Status: RoHS non-compliant
• Number Of Voltages Monitored: 1
• Output: Push-Pull, Push-Pull
• Reset: Active High/Active Low
• Reset Timeout: 35 ms Minimum
• Voltage - Threshold: 4.4V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (3.9mm Width)

ADM8690/ADM8691/ADM8692/ADM8693/ADM8694/ADM8695
APPLICATION INFORMATION
INCREASING THE DRIVE CURRENT
If the continuous output current requirements at V
100 mA, or if a lower V
an external PNP pass transistor can be connected in parallel
with the internal transistor. The BATT ON output (ADM8691/
ADM8693/ADM8695) can directly drive the base of the
external transistor.
USING A RECHARGEABLE BATTERY FOR BACKUP
If a capacitor or a rechargeable battery is used for backup then
the charging resistor should be connected to V
eliminates the discharge path that would exist during power-
down if the resistor is connected to V
ADDING HYSTERESIS TO THE POWER-FAIL
COMPARATOR
For increased noise immunity, hysteresis can be added to the
power-fail comparator. Because the comparator circuit is
noninverting, hysteresis can be added simply by connecting a
resistor between the PFO output and the PFI input as shown in
Figure 26. When PFO is low, Resistor R
summing junction at the PFI pin. When PFO is high, the series
combination of R3 and R4 sources current into the PFI
summing junction. This results in differing trip levels for the
comparator.
5V INPUT
5V INPUT
POWER
POWER
RECHARGEABLE
BATTERY
0.1µF
BATTERY
Figure 24. Increasing the Drive Current
0.1µF
Figure 25. Rechargeable Battery
CC
V
– V
BATT
V
V
CC
V
BATT
PNP TRANSISTOR
I =
CC
OUT
ADM8691/
ADM8693/
V
ADM8695
ADM869x
OUT
voltage differential is desired,
BATT
ON
– V
R
R
CC
BATT
.
3
sinks current from the
V
V
OUT
OUT
OUT
because this
OUT
0.1µF
0.1µF
exceed
Rev. A | Page 14 of 20
PFO
MONITORING THE STATUS OF THE BATTERY
The power-fail comparator can be used to monitor the status of
the backup battery instead of the power supply, if desired. This
is shown in Figure 27. The PFI input samples the battery voltage
and generates an active low PFO signal when the battery voltage
drops below a chosen threshold. It can be necessary to apply a
test load to determine the loaded battery voltage. This is done
under processor control using CE
high during the battery backup mode, the test load is not
applied to the battery while it is in use, even if the
microprocessor is not powered.
BATTERY
7V TO 15V
5V
0V
TEST LOAD
POWER
OPTIONAL
INPUT
0V
20kΩ
Figure 26. Adding Hysteresis to the Power-Fail Comparator
R
R
1
2
V
L
R
R
1
2
V
Figure 27. Monitoring the Battery Status
7805
IN
10MΩ
10MΩ
V
H
5V
PFI
ADM869x
V
PFI
CE
BATT
OUT
1.3V
5V INPUT
ADM869x
V
V
ASSUMING R
HYSTERESIS V
POWER
V
H
L
CC
V
= 1.3V
= 1.3V
CC
OUT
R
3
(
(
1+
. Because CE
1+
PFO
R
R
4
R
R
1
2
CE
< < R
1
2
H
PFO
+
–
– V
IN
R
R
R
3
1
3
3
R
L
)
(1.3V (R
THEN
1
= 5V
LOW BATTERY
SIGNAL TO
MICROPROCESSOR
I/O PIN
FROM
MICROPROCESSOR
I/O PIN APPLIES
TEST LOAD
TO BATTERY
R
(5V – 1.3V)
4
(
TO
MICROPROCESSOR
NMI
OUT
R
R
3
1
2
+ R
)
is forced
4
))
)