THS4532_15 Datasheet, PDF (37/58 Pages) Texas Instruments – THS4532 Ultra Low Power, Rail-to-Rail Output, Fully-Differential Amplifier

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THS4532
SLOS829A – FEBRUARY 2013 – REVISED JULY 2015
9.2 Typical Applications
The following circuits show application information for the THS5432. 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: THS5432 and ADS8321 Combined Performance
No Input V_IN±
Single-Ended
Signal from
Generator and
V_IN+
10 kHz BPF
49.9
2 k
100 pF
0.22 F
2 k
49.9
100 pF
2 k
121
5V
+
V_OCM
±
V_OUT±
THS4532
V_OUT+
2 k
121
220 pF
2.2 nF
220 pF
ADS8321
To Data
Analysis
Figure 87. THS5432 and ADS8321 Test Circuit
9.2.1.1 Design Requirements
To show achievable performance with a high performance SAR ADC, the THS5432 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 87 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 88. 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 THS5432 EVM are modified to implement the schematic in Figure 87 and used
to test the performance of the THS5432 as a drive amplifier. With single supply +5-V supply the output common-
mode of the THS5432 defaults to +2.5 V as required at the input of the ADS8321 so the V_OCM input of the
THS5432 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 THS5432 will make an excellent drive amplifier
for this ADC.
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