THS4531A_16 Datasheet, PDF (35/59 Pages) Texas Instruments – Ultra Low-Power, Rail-to-Rail Output, Fully Differential Amplifier

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THS4531A
SLOS823C – DECEMBER 2012 – REVISED JANUARY 2016
9.2 Typical Applications
The following circuits show application information for the THS4531A. For simplicity, power-supply decoupling
capacitors are not shown in these diagrams; see the Layout Guidelines section for suggested guidelines. For
more details on the use and operation of fully differential amplifiers, refer to the Application Report Fully-
Differential Amplifiers (SLOA054), available for download from the TI website at www.ti.com.
9.2.1 SAR ADC Performance: THS4531A and ADS8321 Combined Performance
No Input V_IN±
Single-Ended
Signal from
Generator and
V_IN+
10 kHz BPF
2k
100 pF
49.9
0.22 F
2k
100 pF
49.9
2k
121
5V
+
V_OCM
±
V_OUT±
THS4531A
V_OUT+
2k
121
220 pF
2.2 nF
220 pF
ADS8321
To Data
Analysis
Figure 85. THS4531A and ADS8321 Test Circuit
9.2.1.1 Design Requirements
To show achievable performance with a high performance SAR ADC, the THS4531A is tested as the drive
amplifier for the ADS8321. The ADS8321 is a 16-bit, SAR ADC that offers excellent AC and DC performance,
with ultra-low power and small size. The circuit shown in Figure 85 is used to test the performance. Data was
taken using the ADS8321 at 100 kSPS with input frequency of 10 kHz and signal levels 0.5 dB below full scale.
The FFT plot of the spectral performance is in Figure 86. A summary of the FFT analysis results are in Table 6
along with ADS8321 typical data sheet performance at f_S = 100 kSPS. Refer to its data sheet for more
information.
9.2.1.2 Detailed Design Procedure
The standard ADS8321 EVM and THS4531A EVM are modified to implement the schematic in Figure 85 and
used to test the performance of the THS4531A as a drive amplifier. With single supply +5-V supply the output
common-mode of the THS4531A defaults to +2.5 V as required at the input of the ADS8321 so the V_OCM input of
the THS4531A simply bypassed to GND with 0.22-µF capacitor. The summary of results of the FFT analysis
versus typical data sheet performance shown in Table 6 show that the THS4531A will make an excellent drive
amplifier for this ADC.
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