TMUX1111 datasheet(26/44 Pages) TI2

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OPA2192

TMUX111x

OUT1

SEL3/

SEL4

IN1

IN2

SEL1/

SEL2

DAC9881

OUT2

SW1

SW2

SW3

SW4

Figure 9-2. 2-Channel Sample-and-Hold Circuit with Pedestal Error Compensation

9.2.1 Design Requirements

The purpose of this precision design is to implement an optimized 2-output sample-and-hold circuit using a

4-channel SPST switch. The sample and hold circuit needs to be capable of supporting high accuracy with

minimized pedestal error and fast settling time..

9.2.2 Detailed Design Procedure

9.2.2.1 Detailed Design Procedure

The TMUX1111, TMUX1112, or TMUX1113 switch is used in conjunction with the voltage holding capacitors (CH)

to implement the sample-and-hold circuit. The basic operation is:

1. When the switch (SW2 or SW3) is closed, it samples the input voltage and charges the holding capacitors

(CH) to the input voltages values.

2. When the switch (SW2 or SW3) is open, the holding capacitors (CH) holds its previous value, maintaining

stable voltage at the amplifier output (VOUT).

Due to switch and capacitor leakage current, as well as amplifier bias current, the voltage on the hold capacitors

droops with time. The TMUX1111, TMUX1112, or TMUX1113 minimize the droops due to its ultra-low leakage

performance. At 25°C, the TMUX1111, TMUX1112, andTMUX1113 have extremely low leakage current at 3pA

typical.

A second switch SW1 (or SW4) is also included to operate in parallel with SW2 (or SW3) to reduce pedestal

error during switch toggling. Because both switches are driven at the same potential, they act as common-mode

signal to the op-amp, thereby minimizing the charge injection effects caused by the switch toggling action.

Compensation network consisting of RC and CC is also added to further reduce the pedestal error, whiling

reducing the hold-time glitch and improving the settling time of the circuit. Refer to Sample and Hold Glitch

Reduction for Precision Outputs Reference Design for more information on sample-and-hold circuits.

TMUX1111, TMUX1112, TMUX1113

SCDS408C – FEBRUARY 2019 – REVISED DECEMBER 2023

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