SN74LV4T125 enable input

Julio Noel Hermandez

Other Parts Discussed in Thread: SN74LV4T125

Hi guys

I am currently working on a project which needs UART port multiplexing and voltage translating from external devices (5V) and MCU (3V3). I was looking at the TI solutions and found SN74LV4T125. This voltage translator is able to enable/disable the input required (up to four) just putting the enable input (OE_n) to low; then, input voltage will be driven to the output according to the voltage supply (VCC).

My plan is put two SN74LV4T125, one for Rx pin (from external device to MCU) and one for Tx pin (from MCU to external device) using the xOE_n as selectors for each devices (four). My question is:

For MCU_Tx pin: If SN74LV4T125 VCC= 5V, what is the pull up voltage of the xOE_n? Is it VCC?

over 9 years ago

0 ShreyasRao over 9 years ago

TI__Guru 62050 points

Hi Julio ,

As you have mentioned , the buffer is enabled with the OE at low and once it is high , the output is disabled (Hi-Z) . The pullup voltage for OE to have the outputs in Hi-Z is determined by the Vcc level . For 5Vcc , the Vih is 2V ,so either 3.3V or 5V will be recognized as high for OE .

0 Julio Noel Hermandez over 9 years ago in reply to ShreyasRao

Intellectual 960 points

Thanks Shreyas

I was worried to damage the MCU, it is well to now that it will be fine =)

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SN74LV4T125 enable input