TMUX1113 datasheet(25/44 Pages) TI2

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9 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, as well as validating and testing their design

implementation to confirm system functionality.

9.1 Application Information

The TMUX11xx family offers ultra-low input/output leakage currents and low charge injection. These devices

operate up to 5.5V, and offer true rail-to-rail input and output of both analog and digital signals. The TMUX111x

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.

9.2 Typical Application - Sample-and-Hold Circuit

One useful application to take advantage of the TMUX1111, TMUX1112, and TMUX1113 performance is the

sample-and-hold circuit. A sample-and-hold circuit can be useful for an analog to digital converter (ADC) to

sample a varying input voltage with improved reliability and stability. It can also be used to store the output

samples from a single digital-to-analog converter (DAC) in a multi-output application. A simple sample-and-hold

circuit can be realized using an analog switch such as the TMUX1111, TMUX1112, and TMUX1113 analog

switches. Figure 9-1 shows a single channel sample-and hold circuit using only 1 of 4 channels in the TMUX111x

devices.

OP AMP

TMUX111x

OUT

SEL1

DAC

(1.8V Capable Control Logic)

SEL4

4 Channels

Figure 9-1. Single Channel Sample-and-Hold Circuit Example

An optional op amp is used before the switch since buffered DACs typically have limitations in driving capacitive

loads. The additional buffer stage is included following the DAC to prevent potential stability problems from

driving a large capacitive load.

Ideally, the switch delivers only the input signals to the holding capacitors. However, when the switch gets

toggled, some amount of charge also gets transferred to the switch output in the form of charge injection,

resulting in a pedestal sampling error. The TMUX1111, TMUX1112, and TMUX1113 switches have excellent

charge injection performance of only -1.5pC, making them excellent choices for this implementation to minimize

sampling error. The pedestal error voltage is indirectly related to the size of the capacitance on the output, for

better precision a larger capacitor is required due to charge injection. Larger capacitance limits the system

settling time which may not be acceptable in some applications. Figure 9-2 shows a TMUX111x device

configured for a 2-channel sample-and-hold circuit with pedestal error compensation.

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TMUX1111, TMUX1112, TMUX1113

SCDS408C – FEBRUARY 2019 – REVISED DECEMBER 2023

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