TXB0106: Concequences if VCCA = VCCB+0.7V

Markku Heinonen

Part Number: TXB0106
Other Parts Discussed in Thread: SN74AXC4T774

We have noticed, that in our design the VCCA of the TXB0106 level translator is connected to +2.5V power supply and SPI interface signals and VCCB is connected to +1.8V supply and interface signals (see the attached picture). The interface is functional, but the supplies do not meet the datasheet's specification for VCCA =< VCCB.

My question is, will there be some consequences for the level translator in this case e.g. will the level translator fail in long term or in high/low temperature or is there current flow from VCCA to VCCB or are some other issues possible?

over 5 years ago

0 Clemens Ladisch over 5 years ago

Guru 316940 points

Section 1.1 of Biasing Requirements for TXS, TXB, and LSF Auto-Bidirectional Translators says:

TXS and TXB-type translators require that V_CCA is less than or equal to V_CCAB. This is due to an internal protection diode that can become forward biased when the voltage on V_CCA exceeds the voltage on V_CCAB. When this occurs, large amounts of current flows through V_CCA and into the diode, increasing power consumption and potentially damaging the device.

0 ShreyasRao over 5 years ago

TI__Guru 62160 points

Hi Markku,

You could consider replacing the TXB0106 to SN74AXC4T774 for the SPI interface as there will be 2 unused channels with the TXB0106 device.

The AXC4T774 supports 1.8 <>2.5V translation.

Pls refer to the video below:

Logic

Logic forum

TXB0106: Concequences if VCCA = VCCB+0.7V