Datasheet

V
IN
SCL
GND
V
A
ADC121C021
REF
[LP2980-2.8]
R
120 nF
20 kÖ
-+
SDA
ALERT
Low
Battery
Indicator
V
BATT
To Controller...
20 kÖ
V
IN
SCL
SDA
ADDR
V
A
ADC121C027
0.1 PF
GND
4.7 PF
R
1
INPUT
Unregulated
Supply
+
-
LMP7731
R
2
LM4132
4.7 PF
R
S
C
S
ADC121C021, ADC121C021Q, ADC121C027
SNAS415F –JANUARY 2008–REVISED MARCH 2013 www.ti.com
BUFFERED INPUT
A buffered input application circuit is shown in Figure 37. The analog input is buffered by a Texas Instruments
LMP7731. The non-inverting amplifier configuration provides a buffered gain stage for a single ended source.
This application circuit is good for single-ended sensor interface. The input must have a DC bias level that keeps
the ADC input signal from swinging below GND or above the supply (+5V in this case).
The LM4132, with its 0.05% accuracy over temperature, is an excellent choice as a reference source for the
ADC121C021.
Figure 37. Buffered Input Circuit
INTELLIGENT BATTERY MONITOR
The ADC121C021 is easily used as an intelligent battery monitor. The simple circuit shown in Figure 38, uses
the ADC121C021, 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
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Product Folder Links: ADC121C021 ADC121C021Q ADC121C027