10.3 Design Requirements

For this design example, use the parameters listed in Table 10-1.

Table 10-1. Design Parameters

PARAMETERS

VALUES

Supply (VDD)

5.0 V

I/O signal range

0 V to VDD (Rail to Rail)

Control logic thresholds

1.8 V compatible

10.4 Detailed Design Procedure

The TMUX1308 and TMUX1309 can operate without any external components except for the supply decoupling

capacitors. If the parts desired power-up state is disabled, then the enable pin should have a weak pull-up

resistor and be controlled by the MCU through the GPIO. All inputs being muxed to the ADC of the MCU must

fall within the recommended operating conditions of the TMUX1308 and TMUX1309, including signal range and

continuous current. For this design with a supply of 5 V, the signal range can be 0 V to 5 V; the maximum

continuous current can be 100 mA at an ambient temperature of 85°C or 25 mA at 125°C.

11 Power Supply Recommendations

The TMUX1308 and TMUX1309 devices operate across a wide supply range of 1.62 V to 5.5 V. Note: do not

exceed the absolute maximum ratings because stresses beyond the listed ratings can cause permanent damage

to the devices.

Power-supply bypassing improves noise margin and prevents switching noise propagation from the VDD

supply to other components. Good power-supply decoupling is important to achieve optimum performance.

For improved supply noise immunity, use a supply decoupling capacitor ranging from 0.1 μF to 10 μF from

VDD to ground. Place the bypass capacitors as close to the power supply pins of the device as possible using

low-impedance connections. TI recommends using multi-layer ceramic chip capacitors (MLCCs) that offer low

equivalent series resistance (ESR) and inductance (ESL) characteristics for power-supply decoupling purposes.

For very sensitive systems, or for systems in harsh noise environments, avoiding the use of vias for connecting

the capacitors to the device pins may offer superior noise immunity. The use of multiple vias in parallel lowers

the overall inductance and is beneficial for connections to ground planes.

12 Layout

12.1 Layout Guidelines

When a PCB trace turns a corner at a 90° angle, a reflection can occur. A reflection occurs primarily because of

the change of width of the trace. At the apex of the turn, the trace width increases to 1.414 times the width. This

increase upsets the transmission-line characteristics, especially the distributed capacitance and self-inductance

of the trace which results in the reflection. Not all PCB traces can be straight; therefore, some traces must turn

corners. Figure 12-1 shows progressively better techniques of rounding corners. Only the last example (BEST)

maintains constant trace width and minimizes reflections.

WORST

BETTER

BEST

1W min.

W

Figure 12-1. Trace Example

www.ti.com

TMUX1308, TMUX1309

SCDS426E – MARCH 2020 – REVISED OCTOBER 2022

Copyright © 2022 Texas Instruments Incorporated

Submit Document Feedback

29

Product Folder Links: TMUX1308 TMUX1309