8.2.1.1 Design Requirements

Table 8-1. TMUX121 I3C Compatibility

I3C Requirements

TMUX121 Specification

Voltage

1.0 V, 1.2 V, 1.8 V, 3.3 V

0-3.6 V

Frequency

Up to 12.5 MHz

3 GHz Bandwidth

Capacitance

50 pF maximum bus capacitance

< 2 pF On or Off Capacitance

8.2.1.2 Detailed Design Procedure

The TMUX121 supports I3C standard by maintaining signal integrity through the switch. Table 8-1 details how

the TMUX121 specifications make this device optimal for switching I3C signals. Choosing a multiplexer with

very low capacitance helps reduces the impact to your total capacitance budget. This can enable more design

flexibility keeping the total bus capacitance under 50 pF such as: longer traces, more ICs, multiple buses, and so

forth.

8.2.1.3 Application Curves

Figure 8-2 shows bandwidth of the TMUX121. This can easily support the max data rate of the I3C standard. A

combination of low on-resistance, low capacitance, and low added jitter from the device allows it to be used for

I3C.

Frequency(Hz)

-6

-5

-4

-3

-2

-1

0

1M

10M

100M

1G

Figure 8-2. Typical Differential Bandwidth vs Frequency

8.3 Power Supply Recommendations

The TMUX121 does not require a power supply sequence. However, TI recommends to enable the device after

VDD is stable and in specification. TI also recommends placing a bypass capacitor as close to the supply pin

VDD as possible to help smooth out lower frequency noise to provide better load regulation across the frequency

spectrum.

8.4 Layout

8.4.1 Layout Guidelines

Place supply bypass capacitors as close to VDD pin as possible and avoid placing the bypass capacitors near

the high speed traces.

Route the high-speed signals using a minimum of vias and corners which reduces signal reflections and

impedance changes. When a via must be used, increase the clearance size around it to minimize its

capacitance. Each via introduces discontinuities in the signal’s transmission line and increases the chance of

picking up interference from the other layers of the board. Be careful when designing test points on twisted pair

lines; through-hole pins are not recommended.

www.ti.com

TMUX121

SCDS381 – AUGUST 2023

Copyright © 2023 Texas Instruments Incorporated

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