ADS8699IPWR datasheet(57/74 Pages) TI2

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8 Application and Implementation

Note

Information in the following applications sections is not part of the TI component specification, and TI

does not warrant its accuracy or completeness. TI’s customers are responsible for determining

suitability of components for their purposes, as well as validating and testing their design

implementation to confirm system functionality.

8.1 Application Information

The ADS869x is a fully-integrated data acquisition (DAQ) system based on a 18-bit successive approximation

(SAR) analog-to-digital converter (ADC). The device includes an integrated analog front-end (AFE) circuit to

drive the inputs of the ADC and an integrated precision reference with a buffer. As such, this device does not

require any additional external circuits for driving the reference or analog input pins of the ADC.

8.2 Typical Application

SAR ADC

Digital Host

Local Power Supply

System Power Supply

Isolated

DC-DC

Converter

GND

IGND

GND

Digital Isolator

Input Signal

Isolation

Barrier

IGND

VINP

VINM

GND

IGND

The potential difference between IGND and GND can be as high as the barrier breakdown voltage (often thousands of volts).

Figure 8-1. 18-Bit Isolated DAQ System for High Common-Mode Rejection

8.2.1 Design Requirements

Design a 18-bit DAQ system for processing input signals up to ±12 V superimposed on large dc or ac common-

mode offsets relative to the ground potential of the system main power supply. The specific performance

requirements are as follows:

• Input signal: ±12-V amplitude signal of a 1-kHz frequency superimposed on a ±75-V common-mode with

frequency between dc and 15 kHz

• CMRR > 100 dB over stipulated common-mode frequency range

• SNR > 91 dB

• THD < –106 dB

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ADS8691, ADS8695, ADS8699

SBAS777B – DECEMBER 2016 – REVISED MARCH 2021

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ADS8699IPWR Datasheet(PDF) 57 Page - Texas Instruments

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