TMUX7462F datasheet(28/37 Pages) TI

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8.3.3 Overvoltage Fault Flags

The voltages on TMUX7462F's source input pins are continuously monitored, and the status of whether an

overvoltage condition occurs is indicated by an active low general fault flag (FF). The voltage on the FF pin

indicates if any of the source input pins are experiencing an overvoltage condition. If any source pin voltage

exceeds the fault supply voltages by a VT, the FF output is pulled-down to below VOL. The FF pin is an

open-drain output, and external pull-up resistors of 1 kΩ are recommended. The pull-up voltage can be in the

range of 1.8 V to 5.5 V, depending on the controller voltage the device interfaces with.

8.3.4 Bidirectional Operation

The TMUX7462F conducts equally well from source (Sx) to drain (Dx) or from drain (Dx) to source (Sx). Each

signal path has very similar characteristics in both directions; however, it is noted that the overvoltage protection

is implemented only on the source (Sx) side. The voltage on the drain is only allowed to swing between VFP and

VFN and no overvotlage protection is available on the drain side.

The primary supplies (VDD and VSS) define the on-resistance profile of the switch channel, whereas the fault

voltage supplies (VFP and VFN) define the signal range that can be passed through from source to drain of the

device. It is good practice to use voltages on VFP and VFN that are lower than VDD and VSS to take advantage

of the flat on-resistance region of the device for better input-to-output linearity. The flatest on-resistance region

extends from VSS to roughly 3 V below VDD. Once the signal is within 3 V of VDD the on-resistance will

expoentially increase and may impact desired signal transmission.

8.4 Device Functional Modes

The TMUX7462F offers two modes of operation (Normal mode and Fault mode) depending on whether any of

the input pins experience an overvoltage condition.

8.4.1 Normal Mode

In Normal mode operation, signals of up to VFP and VFN can be passed through the switch from source (Sx) to

drain (Dx) or from drain (Dx) to source (Sx). The following conditions must be satisfied for the switch to stay in

the ON condition:

• The difference between the primary supples (VDD – VSS) must be higher or equal to 8 V.

• VFP must be between 3 V and VDD, and VFN must be between VSS and 0 V.

• The input signals on the source (Sx) or the drain (Dx) must be between VFP+ VT and VFN – VT.

8.4.2 Fault Mode

The TMUX7462F enters into the Fault mode when any of the input signals on the source (Sx) pins exceed VFP

or VFN by a threshold voltage VT. The switch input experiencing the fault automatically turns off, and the source

pin becomes high impedance with negligible amount of leakage current flowing through the switch under the

overvoltage condition. Section 8.3.2.4 describes how the drain pin (Dx) behavior under the Fault mode can be

programmed. The general fault flag (FF) is asserted low in the Fault mode.

The overvoltage protection is provided only for the source (Sx) input pins. The drain (Dx) pin, if used as signal

input, must stay in between VFP and VFN at all time since no overvoltage protection is implemented on the drain

pin.

8.4.3 Truth Table

Table 8-1 shows the truth tables for the TMUX7462F. Each switch is independently controlled by its own select

pin.

Table 8-1. TMUX7462F Truth Table

DR PIN STATE

Dx State During Fault

Condition

Pulled up to VFP or VFN

Open (HI-Z)

TMUX7462F

SCDS394A – MARCH 2021 – REVISED OCTOBER 2021

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