The TMUX1109 can operate without any external components except for the supply decoupling capacitors. If the device desired power-up state is disabled, then the enable pin should have a weak pull-down resistor and be controlled by the MCU through the GPIO. All inputs being muxed to the ADC must fall within the recommend operating conditions of the TMUX1109 including signal range and continuous current. System level design and component selection are made according to True Differential, 4 x 2 MUX, Analog Front End, Simultaneous-Sampling ADC Circuit.

1. The ADS9224R was selected because of the dual simultaneous sampling and high throughput (3-MSPS).
2. The TMUX1109 4:1 (2x) multiplexer was selected to support 4 differential inputs for each ADC.
3. Find ADC full-scale range, resolution and common-mode range specifications.
4. Determine the linear range of the FDA (THS4551) based on common-mode and output swing specification.
5. Select COG capacitors for all filter capacitors at the ADC input to minimize distortion.
6. Select the FDA gain resistors RF1,2 , RG1,2. Use 0.1% 20ppm/°C film resistors or better for good accuracy, low gain drift and to minimize distortion.
7. Introduction to SAR ADC Front-End Component Selection covers the methods for selecting the charge bucket circuit Rfil1, Rfil1 and Cfil. These component values are dependent on the amplifier bandwidth, data converter sampling rare, and data converter design. The values shown here will give good settling and AC performance for the amplifier and data converter in this example. If the design is modified, a different RC filter must be selected.
8. The THS4551 is commonly used in high-speed precision fully differential SAR applications as it has sufficient bandwidth to settle to charge kickback transients from the ADC input sampling, and multiplexer charge injection and provides the common-mode level shifting to the voltage range of the SAR ADC.
9. The TMUX1109 is used in high-speed precision fully differential SAR applications as it has sufficient bandwidth, low charge injection, and low on-resistance and capacitance. Low capacitance supports fast switching between channels and allows the system to settle within required precision in the specified timing.