8.3 Feature Description

8.3.1 1.2-V Logic Compatible Inputs

inputs allow the TMUX646 to interface with processors that have lower logic I/O rails and eliminates the need for

an external voltage translator, which saves both space and BOM cost. For more information on 1.2 V and 1.8 V

logic implementations, refer to Simplifying Design with 1.8 V logic Muxes and Switches.

8.3.2 Bidirectional Operation

The TMUX646 conducts equally well from A to COM, B to COM, COM to A, or COM to B. Each channel has very

similar characteristics in both directions and supports analog and digital signals.

8.3.3 Powered-Off Protection

high impedance state. The crosstalk, off-isolation, and leakage will remain within the electrical specifications.

This prevents errant voltages from reaching the rest of the system and maintains isolation when the system is

powering up:

Figure 8-1 shows an example system containing a switch without powered-off protection with the following

system level scenario.

1. Subsystem A powers up and starts sending information to Subsystem B that remains unpowered.

2. The I/O voltage back powers the supply rail in Subsystem B.

3. The digital logic is back powered and turns on the switch. The signal is transmitted to Subsystem B before it

is powered and damages it.

Subsystem A

Subsystem B

Powered

LDO

Switch

SEL

VDD

Unpowered

ESD

1

2

3

Figure 8-1. System Without Powered-Off Protection

With powered-off protection, the switch prevents back powering the supply and the switch remains high-

impedance. Subsystem B remains protected.

Subsystem A

Subsystem B

Powered

LDO

Switch

SEL

VDD

Unpowered

ESD

2

Protection

Hi-Z

Figure 8-2. System With Powered-Off Protection

TMUX646

SCDS432 – JUNE 2021

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