MUX36S08 Datasheet, PDF (26/37 Pages) Texas Instruments – Low-Capacitance, Low-Leakage-Current, Precision, Analog Multiplexers

MUX36S08, MUX36D04
SBOS705A – JANUARY 2016 – REVISED JANUARY 2015
www.ti.com
10 Applications and Implementation
10.1 Application Information
The MUX36xxx 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 MUX36xxx is
very low. These features makes the MUX36xxx a precision, robust, high-performance analog multiplexer for high-
voltage, industrial applications.
10.2 Typical Application
Figure 42 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 mux. This TI Precision
Design details the process for optimizing the precision, high-voltage, front-end drive circuit using the MUX36D04,
OPA192 and OPA140 to achieve excellent dynamic performance and linearity with the ADS8864.
Analog Inputs
Bridge Sensor
Thermocouple
Current Sensing
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, 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 20 V and frequency
(f_IN) of 10 kHz are applied to each differential input of the mux.
10.2.2 Detailed Design Procedure
The purpose of this precision design is to design an optimal, high-voltage, multiplexed, data-acquisition system
for highest system linearity and fast settling. The overall system block diagram is illustrated in Figure 42. The
circuit is a multichannel, data-acquisition signal chain consisting of an input low-pass filter, mux, mux output
buffer, attenuating SAR ADC driver, and the reference driver. The architecture allows fast sampling of multiple
channels using a single ADC, providing a low-cost solution. This design systematically approaches each analog
circuit block to achieve a 16-bit settling for a full-scale input stage voltage and linearity for a 10-kHz sinusoidal
input signal at each input channel. Detailed design considerations and component selection procedure can be
found in the TI Precision Design TIPD151, 16-Bit, 400-kSPS, 4-Channel Multiplexed Data-Acquisition System for
High-Voltage Inputs with Lowest Distortion.
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