Datasheet
ADC1213X
V
A
+
LM4040-4.1
(LM4040-2.5)
1k
+5.0V
(+3.3V)
V
D
+
V
REF
+
V
REF
-
+4.1V
(+2.5V)
DGNDAGND
ANALOG INPUT VOLTAGE
GROUND REFERENCE
CH0
CH2
CH4
or
CH6
CH1
CH3
CH4
or
CH7
ANALOG INPUT VOLTAGE RANGE
0.45V to 4.55V
(0.4V to 2.9V)
ASSIGNED
(+) INPUT
ANALOG INPUT VOLTAGE RANGE
0.45V to 4.55V
(0.4V to 2.9V)
ASSIGNED
(-) INPUT
FULLY DIFFERENTIAL
12-BIT PLUS SIGN
0.01 uF 0.1 uF 10 uF
0.01 uF 0.1 uF 10 uF
0.01 uF 0.1 uF 10 uF
ADC12130, ADC12132, ADC12138
www.ti.com
SNAS098G –MARCH 2000–REVISED MARCH 2013
Figure 73. Fully Differential Biasing
3.0 REFERENCE VOLTAGE
The difference in the voltages applied to the V
REF
+
and V
REF
−
defines the analog input span (the difference
between the voltage applied between two multiplexer inputs or the voltage applied to one of the multiplexer
inputs and analog ground) over which 4095 positive and 4096 negative codes exist. The voltage sources driving
V
REF
+
and V
REF
−
must have very low output impedance and noise. The circuit in Figure 74 is an example of a
very stable reference appropriate for use with the device.
*Tantalum
Figure 74. Low Drift Extremely
Stable Reference Circuit
The ADC12130/2/8 can be used in either ratiometric or absolute reference applications. In ratiometric systems,
the analog input voltage is proportional to the voltage used for the ADC's reference voltage. When this voltage is
the system power supply, the V
REF
+
pin is connected to V
A
+
and V
REF
−
is connected to ground. This technique
relaxes the system reference stability requirements because the analog input voltage and the ADC reference
voltage move together. This maintains the same output code for given input conditions. For absolute accuracy,
where the analog input voltage varies between very specific voltage limits, a time and temperature stable voltage
source can be connected to the reference inputs. Typically, the reference voltage magnitude will require an initial
adjustment to null reference voltage induced full-scale errors.
Below are recommended references along with some key specifications.
Copyright © 2000–2013, Texas Instruments Incorporated Submit Documentation Feedback 37
Product Folder Links: ADC12130 ADC12132 ADC12138