MUX508 Datasheet, PDF (26/37 Pages) Texas Instruments – Low-Capacitance, Low-Charge-Injection, Precision, Analog Multiplexers

MUX508, MUX509
SBAS758A – JANUARY 2016 – REVISED MARCH 2016
10 Applications and Implementation
www.ti.com
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.
Analog Inputs
Bridge Sensor
Thermocouple
Current Sensing
MUX509
OPA192
+
+
OPA192
Gain Network
Gain Network
Gain Network
OPA192
+
REF3140
RC Filter OPA350
Reference Driver
RC Filter
Antialiasing
Filter
VINP
REF
ADS8864
VINM
Photo
LED ^Detector
Optical Sensor
High-Voltage Multiplexed Input
High-Voltage Level Translation
VCM
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
(f_IN) of 10 kHz are applied to each differential input of the mux.
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