Adc Input Signal Driver; Figure 2-1. Ads8354Evm Analog Input Path - Texas Instruments ADS8354EVM-PDK User Manual

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2.2 ADC Input Signal Driver

The SAR ADC inputs terminate in switched-capacitor networks that create large instantaneous current loads
when the switches are closed, which effectively makes the ADC inputs dynamically low impedance. The analog
inputs of the ADC are therefore driven by an THS4561 used with a gain of 1 V/V configuration to maintain ADC
performance with maximum loading at full device throughput of the ADS8354 of 700 kSPS.
2.2.1 Input Signal Path
Figure 2-1 shows the signal path for the analog inputs applied to the ADS8354EVM. Separate THS4561
amplifiers are used with a gain of 1 V/V configuration to drive the individual analog inputs (AINP and AINM)
of each ADC. The OPA320 amplifier circuits help drive the common-mode voltage (VOCM) of the THS4561
amplifiers. An RC filter, with values of R
selected to achieve a SINAD greater than 88 dB and a THD less than –97 dB for a 2-kHz sine-wave input at full
throughput of the ADS8354 of 700 kSPS.
SBAU407 – APRIL 2023
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= 13 Ω, differential C
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Figure 2-1. ADS8354EVM Analog Input Path

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= 820 pF, and common-mode C
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ADS8354EVM-PDK Evaluation Module
Analog Interface
= 10 pF, was
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