8.3.3 1.8 V Logic Compatible Inputs

The TMUX1248 has 1.8 V logic compatible control for the logic control input (SEL). The logic input threshold

scales with supply but still provides 1.8 V logic control when operating at 5.5 V supply voltage. 1.8 V logic

level inputs allow the TMUX1248 to interface with processors that have lower logic I/O rails and eliminates the

need for an external translator, which saves both space and BOM cost. For more information on 1.8 V logic

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

8.3.4 Fail-Safe Logic

The TMUX1248 supports Fail-Safe Logic on the control input pin (SEL) allowing for operation up to 5.5 V,

regardless of the state of the supply pin. This feature allows voltages on the control pin to be applied before the

supply pin, or allows higher voltages on the SEL pin up to 5.5 V, protecting the device from potential damage.

Fail-Safe Logic minimizes system complexity by removing the need for power supply sequencing on the logic

control pin. For example, the Fail-Safe Logic feature allows the select pin of the TMUX1248 to be ramped to 5.5

the select pin to interface with a logic level of another device up to 5.5 V.

8.4 Device Functional Modes

The select (SEL) pin of the TMUX1248 controls which switch is connected to the drain of the device. When a

given input is not selected, that source pin is in high impedance mode (HI-Z). The control pins can be as high as

5.5 V.

The TMUX1248 can be operated without any external components except for the supply decoupling capacitors.

additional current as highlighted in Implications of Slow or Floating CMOS Inputs. Unused signal path inputs (Sx

or D) should be connected to GND.

8.5 Truth Tables

Table 8-1. TMUX1248 Truth Table

CONTROL

LOGIC (SEL)

Selected Source (Sx) Connected To Drain (D) Pin

0

S1

1

S2

TMUX1248

SCDS447 – JULY 2021

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