Datasheet

CM+1/2V
REF
+1/2V
REF
- V
REF
1/2
Single-EndedInputs
t
INP
CMVoltage
CM V-
REF
1/2
CM+1/2V
REF
DifferentialInputs
t
INP
INN
CMVoltage
CM 1/2V
REF
-
+V
REF
-V
REF
Common-ModeVoltage(DifferentialMode)=
(INP)+(INN)
2
,Common-ModeVoltage(Single-EndedMode)= INN.
INN=CMVoltage
InputRange(DifferentialMode)=(AINP AINN)=2V .-
REF
Device
- V to
+1/2 V
1/2
REF
REF
Common
Voltage
Single-Ended Input
Device
V
Peak-to-Peak
REF
V
Peak-to-Peak
REF
Common
Voltage
Differential Input
ADS1291
ADS1292
ADS1292R
SBAS502B –DECEMBER 2011–REVISED SEPTEMBER 2012 www.ti.com
ANALOG INPUT
The ADS1291, ADS1292, and ADS1292R analog input is fully differential. Assuming PGA = 1, the differential
input (INP – INN) can span between –V
REF
to +V
REF
. Note that the absolute range for INP and INN must be
between AVSS – 0.3 V and AVDD + 0.3 V. Refer to Table 10 for an explanation of the correlation between the
analog input and the digital codes. There are two general methods of driving the ADS1291, ADS1292, and
ADS1292R analog input: single-ended or differential, as shown in Figure 21 and Figure 22. Note that INP and
INN are 180°C out-of-phase in the differential input method. When the input is single-ended, the INN input is held
at the common-mode voltage, preferably at mid-supply. The INP input swings around the same common voltage
and the peak-to-peak amplitude is (common-mode + 1/2 V
REF
) and (common-mode – 1/2 V
REF
). When the input
is differential, the common-mode is given by (INP + INN) / 2. Both INP and INN inputs swing from (common-
mode + 1/2 V
REF
to common-mode – 1/2 V
REF
). For optimal performance, it is recommended that the ADS1291,
ADS1292, and ADS1292R be used in a differential configuration.
Figure 21. Methods of Driving the ADS1291, ADS1292, and ADS1292R: Single-Ended or Differential
Figure 22. Using the ADS1291, ADS1292, and ADS1292R in Single-Ended and Differential Input Modes
20 Submit Documentation Feedback Copyright © 2011–2012, Texas Instruments Incorporated
Product Folder Links: ADS1291 ADS1292 ADS1292R