9.3 Design Requirements

For this design example, use the parameters listed in Table 9-1.

Table 9-1. Design Parameters

PARAMETERS

VALUES

5.0 V

I/O signal range

Control logic thresholds

1.8 V compatible

9.4 Detailed Design Procedure

The TMUX1308 and TMUX1309 can be operated without any external components except for the supply

decoupling capacitors. If the parts desired power-up state is disabled, 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 recommend 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 max continuous

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

10 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.

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

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.

11 Layout

11.1 Layout Guidelines

11.1.1 Layout Information

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 11-1 shows progressively better techniques of rounding corners. Only the last example (BEST)

maintains constant trace width and minimizes reflections.

TMUX1308, TMUX1309

SCDS426C – MARCH 2020 – REVISED AUGUST 2020

www.ti.com

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