Datasheet

TIME
VOLTAGE
Measured
Battery
Voltage
V
LOW
Limit
ALERT pin
(Active Low)
DISCHARGE CYCLE
V
IN
SCL
GND
V
A
ADC081C021
REF
[LP2980-2.8]
R
120 nF
20 kÖ
-+
SDA
ALERT
Low
Battery
Indicator
V
BATT
To Controller...
20 kÖ
TIME
VOLTAGE
Measured
Battery
Voltage
V
High
Limit
ALERT pin
(Active Low)
RECHARGE CYCLE
V
IN
SCL
SDA
ADDR
V
A
ADC081C027
0.1 PF
GND
4.7 PF
R
1
INPUT
Unregulated
Supply
+
-
LMP7731
R
2
LM4132
4.7 PF
R
S
C
S
ADC081C021, ADC081C027
www.ti.com SNAS447C –FEBRUARY 2008–REVISED MARCH 2013
Figure 37. Buffered Input Circuit
INTELLIGENT BATTERY MONITOR
The ADC081C021 is easily used as an intelligent battery monitor. The simple circuit shown in Figure 38, uses
the ADC081C021, the LP2980 fixed reference, and a resistor divider to implement an intelligent battery monitor
with a window supervisory feature. The window supervisory feature is implemented by the "out of range" alert
function. When the battery is recharging, the Over Range Alert will indicate that the charging cycle is complete
(see Figure 39). When the battery is nearing depletion, the Under Range Alert will indicate that the battery is low
(see Figure 40).
Figure 38. Intelligent Battery Monitor Circuit Figure 39. Recharge Cycle
Figure 40. Discharge Cycle
In addition to the window supervisory feature, the ADC081C021 will allow the controller to read the battery
voltage at any time during operation.
Copyright © 2008–2013, Texas Instruments Incorporated Submit Documentation Feedback 31
Product Folder Links: ADC081C021 ADC081C027