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  • TI Thinks Resolved

lsf204 3.3v to 5 v translator

Im using lsf204 for translator for two applications with tssop package footprint and low power.

Vref_A = 3.3V

Vref_B = 5V.

1) case 1:

A-side has 2 open drain input but the board already have 10K pullups on board and 2 push-pull inputs. This is for low speed interrtupt signal.

3.3V -- 5V

od1_pu ->

od2_pu ->

pushpull1 ->

pushpull2 ->

B-side doesn't have any pullup so look like the level doesn't reach 5V.

would I need add pullup or perhaps change to:

txb104: pushpull is ok, but does open drain work since I have external pullups?

txsb0104: This has builtin pullup so it should work for open drain. it mentions itnshould wirk for pushpull as well.

2) case 2:

serial port 3.3V to 5V push-pull rx, tx,cts, rts.

Again look like for output on 5V side, I need pullup.

3.3V -- 5V

tx ->

rx <-

rts <-

clt ->

in this case perharps txb104 or txsb0104 should  work as footprint is the same in tssop package with EN active high.

  • I think I need to stick to LSF204 since the enble pin is tied to VrefB 5V. Other two devices are designed to tie to Vcc_A, which has max limit of 4.5V.

    I'm curious to see if my MCU internal pullup of 20K to 50K ia strong enough.
  • I think I need to stick to LSF204 since the enble pin is tied to VrefB 5V. Other two devices are designed to tie to Vcc_A, which has max limit of 4.5V.

    I'm curious to see if my MCU internal pullup of 20K to 50K is strong enough.
  • Hi Khoi,

    Have you read through the application report, 

    I think this would help you a great deal.


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