OPA4191IPWR datasheet(33/65 Pages) TI2

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9.2.2 16-Bit Precision Multiplexed Data-Acquisition System

Figure 9-4 shows a 16-bit, differential, 4-channel, multiplexed, data-acquisition system. This example is typical

in industrial applications that require low distortion and a high-voltage differential input. The circuit uses the

ADS8864, a 16-bit, 400-kSPS successive-approximation-resistor (SAR), analog-to-digital converter (ADC), along

with a precision, high-voltage, signal-conditioning front-end, and a 4-channel differential multiplexer (mux). This

application example shows the process for optimizing the precision, high-voltage, front-end drive circuit using the

OPA191 and OPA140 to achieve excellent dynamic performance and linearity with the ADS8864. The full design

can be found in TI Precision Design TIPD151, 16-Bit, 400-kSPS, Four-Channel MUX Data Acquisition System

for High-Voltage Inputs.

SAR

ADC

REFP

VINP

VINM

4:2

Mux

Antialiasing

Filter

Gain

Network

Gain

Network

High-Voltage Level Translation

VCM

High-Voltage Multiplexed Input

Reference Driver

Voltage

Reference

RC Filter

Buffer

RC Filter

16 Bits

400 kSPS

Delay

Digital Counter For Multiplexer

CONV

Very Low Output Impedance

Input-Filter Bandwidth

High-Impedance Inputs

No Differential Input Clamps

Fast Settling-Time Requirements

Attenuate High-Voltage Input Signal

Fast-Settling Time Requirements

Stability of the Input Driver

Attenuate ADC Kickback Noise

VREF Output: Value and Accuracy

Low Temp and Long-Term Drift

Fast logic transition

±20-V,

10-kHz

Sine Wave

±20-V,

10-kHz

Sine Wave

Shmidtt

Trigger

Counter

REF3240

Voltage

Divider

OPA350

VCM Generation Circuit

CH0+

CH0-

CH3+

CH3-

OPA191

OPA140

OPA191

Gain

Network

Figure 9-4. OPA191 in 16-Bit, 400-kSPS, 4-Channel, Multiplexed Data Acquisition System for High-Voltage

Inputs With Lowest Distortion

9.2.2.1 Design Requirements

The primary objective is to design a ±20-V, differential, 4-channel, multiplexed, data acquisition system with

lowest distortion using the 16-bit ADS8864 at a throughput of 400 kSPS for a 10-kHz, full-scale, pure sine-wave

input. The design requirements for this block design are:

• System supply voltage: ±15 V

• ADC supply voltage: 3.3 V

• ADC sampling rate: 400 kSPS

• ADC reference voltage (REFP): 4.096 V

• System input signal: A high-voltage differential input signal with a peak amplitude of 10 V and frequency (fIN)

of 10 kHz are applied to each differential input of the mux.

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OPA191, OPA2191, OPA4191

SBOS701D – DECEMBER 2015 – REVISED AUGUST 2021

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