ADS8864

REF

VINP

VINM

+

+

+

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

MUX509

Copyright © 2016, Texas Instruments Incorporated

27

MUX508, MUX509

www.ti.com

SBAS758C – JANUARY 2016 – REVISED SEPTEMBER 2016

Product Folder Links: MUX508 MUX509

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Copyright © 2016, Texas Instruments Incorporated

10 Applications 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. Customers should

validate and test their design implementation to confirm system functionality.

10.1 Application Information

The MUX50x family offers outstanding input/output leakage currents and ultralow 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 precision, robust, high-performance analog multiplexer for high-voltage,

industrial applications.

10.2 Typical Application

Figure 42 shows a 16-bit, differential, four-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 four-channel differential mux. This application

example details the process for optimizing a precision, high-voltage, front-end drive circuit using the MUX509,

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

10.2.1 Design Requirements

The primary objective is to design a ±20 V, differential, four-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

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