ADS8864

REF

+

+

+

Charge

Kickback

Filter

Gain Network

Gain Network

Gain Network

High-Voltage Level Translation

VCM

High-Voltage Multiplexed Input

Reference Driver

REF3140

RC Filter

OPA350

RC Filter

Analog Inputs

LED

Photo

Detector

Bridge Sensor

Thermocouple

Current Sensing

Optical Sensor

OPA192

OPA192

OPA140

Copyright © 2016, Texas Instruments Incorporated

28

MUX506, MUX507

SBAS803 – NOVEMBER 2016

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Copyright © 2016, Texas Instruments Incorporated

9 Applications and Implementation

9.1 Application Information

The MUX50x family offers outstanding input/output leakage currents and ultra-low charge injection. These

devices operate up to 36 V, and offer true rail-to-rail input and output. The on-capacitance of the MUX50x is very

low. These features makes the MUX50x a family of precision, robust, high-performance analog multiplexer for

high-voltage, industrial applications.

9.2 Typical Application

Figure 42 shows a 16-bit, differential, 8-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 mux. This TI Precision

Design details the process for optimizing the precision, high-voltage, front-end drive circuit using the MUX507,

OPA192 and OPA140 to achieve excellent dynamic performance and linearity with the ADS8864.

Figure 42. 16-Bit Precision Multiplexed Data-Acquisition System for High-Voltage Inputs With Lowest

Distortion

9.2.1 Design Requirements

The primary objective is to design a ±20 V, differential, 8-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 20 V and frequency