ADS7041_15 Datasheet, PDF (26/42 Pages) Texas Instruments – Ultra-Low Power, Ultra-Small Size, 10-Bit, 1-MSPS, SAR ADC

ADS7041
SBAS675C – NOVEMBER 2014 – REVISED DECEMBER 2015
Typical Applications (continued)
9.2.2 DAQ Circuit with the ADS7041 for Maximum SINAD
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+
V_IN+
±
OPA_AVDD
+ ^{OPA835 25}
OPA_AVSS
1.5 nF
AVDD
AINP
AVDD
Device
AINM
GND
Input Driver
Device: 10-Bit, 1-MSPS,
Single-Ended Input
Figure 42. ADS7041 DAQ Circuit: Maximum SINAD for Input Frequencies up to 250 kHz
9.2.2.1 Design Requirements
The goal of this application is to design a data acquisition circuit based on the ADS7041 with SINAD greater than
61 dB for input frequencies up to 250 kHz.
9.2.2.2 Detailed Design Procedure
To achieve a SINAD of 61 dB, the operational amplifier must have high bandwidth in order to settle the input
signal within the acquisition time of the ADC. The operational amplifier must have low noise to keep the total
system noise below 20% of the input-referred noise of the ADC. For the application circuit shown in Figure 42,
the OPA835 is selected for its high bandwidth (56 MHz) and low noise (9.3 nV/√Hz).
For a step-by-step design procedure, circuit schematics, bill of materials, PCB files, simulation
results, and test results, refer to TI Precision Design TIPD168, Three 12-Bit Data Acquisition
Reference Designs Optimized for Low Power and Ultra-Small Form Factor (TIDU390).
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