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TXS0108E: output issue of TXS0108

user1748595
Prodigy 70 points
Part Number: TXS0108E

Hi，

the TXS0108 was used to translate the level from 3.3v to 5v on the SPI_CLK signal. The CPU is STM32F427 and the output was set to PUSHPULL.

i found that the input of the TXS0108 is right, but the output was wrong,even i try all of the follow method:

1.change the RP7 from 33R to 0R

2.remove the RP2 so the TXS is isolated with the SPI device

3.remove the RP7 then input another SPI-CLK from a normal development board(the cpu is stm32f401)

  • 0
    Guru 316600 points

    It is impossible to tell what is going on without seeing a schematic of your circuit, but I'd guess that the pull-up resistor is too large.

  • 0
    TI__Guru* 97046 points

    Hi,

    It looks to me like the load of the TXS device is a fairly large capacitance. Doing a quick calculation from the shown waveform and knowing that there is a 10kΩ resistor inside the TXS0108E gives a capacitance of ~50pF.

    Adding an external 1kΩ pull-up resistor could significantly improve the up-translation waveform, assuming I am correct about the issue in your circuit (without actually seeing the schematic...).