THS4521 datasheet(39/58 Pages) TI2

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−140

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−90

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−50

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−10

10k

20k

30k

40k

50k

Frequency (Hz)

VS = 5 V

G = 1 V/V

RF = 2 k

Ω

VOUT = −0.5 dBFS

G078

2 k

0.22 F

THS4531

VOUT+

121

VOUT–

121

Single-Ended

Signal from

Generator and

10 kHz BPF

VIN+

VIN–

–

VOCM

2 k

2.2 nF

2 k

To Data

Analysis

ADS8321

100 pF

220 pF

No Input

49.9

THS4531

www.ti.com

SLOS358C – SEPTEMBER 2011 – REVISED APRIL 2020

Product Folder Links: THS4531

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SAR ADC Performance (continued)

Figure 89. THS4531 and ADS8321 Test Circuit

Figure 90. THS4531 + ADS8321 1-kHz FFT

Table 7. 10 kHz FFT Analysis Summary

CONFIGURATION

TONE

SIGNAL

SNR

THD

SINAD

SFDR

THS4531 + ADS8321

10 kHz

-0.5 dBFS

87 dBc

-96 dBc

87 dBc

100 dBc

ADS8321 data sheet (typical)

10 kHz

-0.5 dBFS

87 dBc

-86 dBc

84 dBc

86 dBc

9.4.2 THS4531 and ADS7945 Combined Performance

To show achievable performance with a high performance SAR ADC, the THS4531 is tested as the drive

amplifier for the ADS7945. The ADS7945 is a 14-bit, SAR ADC that offers excellent AC and DC performance,

with low power and small size. The circuit shown in Figure 91 is used to test the performance. Data was taken

using the ADS7945 at 2MSPS with input frequency of 10 kHz and signal level 0.5 dB below full scale. The FFT

plot of the spectral performance is in Figure 92. A summary of the FFT analysis results are in Table 8 along with

ADS7945 typical data sheet performance at fS = 2 MSPS. Please refer to its data sheet for more information.

The standard ADS7945 EVM and THS4531 EVM are modified to implement the schematic in Figure 91 and used

to test the performance of the THS4531 as a drive amplifier. With single supply +5 V supply the output common-

mode of the THS4531 defaults to +2.5 V as required at the input of the ADS7945 so the VOCM input of the

THS4531 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 8 show the THS4531 will make an excellent drive amplifier for

this ADC.

THS4521 Datasheet(PDF) 39 Page - Texas Instruments

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