+

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SEL

Processor

1.8V Logic I/O

0.1µF

Gain / Filter

Network

Digital Processing

ADC

OP

AMP

19

TMUX1101, TMUX1102

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SCDS410 – MARCH 2019

Product Folder Links: TMUX1101 TMUX1102

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Copyright © 2019, Texas Instruments Incorporated

10 Application 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 TMUX11xx family offers ulta-low input/output leakage currents and low charge injection. These devices

operate up to 5.5 V, and offer true rail-to-rail input and output of both analog and digital signals. The TMUX110x

have a low on-capacitance which allows faster settling time when multiplexing inputs in the time domain. These

features make the TMUX11xx devices a family of precision, high-performance switches and multiplexers for low-

voltage applications.

10.2 Typical Application

Switches and multiplexers are commonly used in the feedback path of amplifier circuits to provide configurable

gain control. By using various resistor values on the switch path the TMUX110x allows the system to have

multiple gain settings. An external resistor ensures the amplifier isn't operating in an open loop configuration. A

transimpedance amplifier (TIA) for photodiode inputs is a common circuit that requires gain control using a switch

to convert the output current of the photodiode into a voltage for the MCU or processor. The amount of light

present during a photodiode measurement is dependent on the time of day and available light source, an

external switch such as the TMUX110x can be utilized to increase the gain when a smaller photodiode current is

present.The leakage current, capacitance, and charge injection performance of the TMUX110x are key

specifications to evaluate when selecting a device for gain control.

Figure 10. Configurable Gain Setting of a TIA circuit