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TXS0102-Q1: impact when the VCCA ≤ VCCB condition is not met?

Julio Apps
Expert 3665 points
Part Number: TXS0102-Q1

A question has come up regarding the TXS0102-Q1; Specifically regarding the note about “A VCCA value greater than or equal to VCCB (VCCA ≥ VCCB) does not damage the device, but during operation, VCCA must be less than or equal to VCCB (VCCA ≤ VCCB) at all times.”

 

There are some instances in the this design where VCCA and VCCB are both at 3V3 but sourced from 2 separate power domains, with slight variations that can be expected on either rail. Hence there will not likely be a way to guarantee VCCA <= VCCB.

 

My question is what is the impact when the VCCA ≤ VCCB condition is not met? Do you have any recommendations for devices that can be used alternatively for this application?

  • 0
    Guru 316690 points

    VCCA and VCCB Bias Requirements for Bidirectional Translators (SCEA060) says:

    TXS and TXB-type translators require that VCCA is less than or equal to VCCB. This is due to an internal protection diode that can become forward biased when the voltage on VCCA exceeds the voltage on VCCB. […] VCCB fixed at 2.5 V and VCCA swept from 2.5 V to 3.5 V:

    As shown in Figure 4, … when the voltage on VCCA exceeds the voltage on VCCB by roughly 0.6 V, the diode begins to conduct and the ICCA current begins to drastically increase as VCCA increases.

  • 0 in reply to Clemens Ladisch
    TI__Guru 62030 points

    Thanks Clemens.

    In general, If both supplies are at same level, it should be fine;although you may not need the level translator in such cases.