TXS0108E:level shifter 5v to 3.3V

francesc riera vidal

Part Number: TXS0108E

Hello everyone.

I am trying to run the bldc motors of an old cnc using step and direction pulses.
Everything works fine, but I have a loss of step signal.

I use an arduino uno with Estlcam to generate the pulses
, I have mounted a 5v to 3.3v converter (txs0108E) on this one to send the pulses to the stm32f446 and IHM07M1 driver assembly.

Capturing the signal I have realized that the High Voltage level (3V) output of the converter is just over 2V (2.09v). If I don’t connect the output to the stm board it is 3V.
I don’t know if putting a pull up resistor at the output would be a good idea.
What do you recommend?

Thanks

5 months ago

0 Clemens Ladisch 5 months ago

Guru 272490 points

The TXS has open-drain outputs.

Use a level shifter with push/pull outputs like the TXU104.

0 Jack Guan 5 months ago

TI__Mastermind 23651 points

Hey Francesc,

It seems like you may have pulldowns internal to the stm32f446/ IHM07M1. In any case, any external pullups/ pulldown on the I/Os of the TXS0108E can result in a voltage divider network as seen in this app note: Effects of External Pullup and Pulldown Resistors on TXS and TXB Devices.

Please suggest Clemens' recommendation instead.

Regards,

Jack

0 francesc riera vidal 5 months ago in reply to Jack Guan

Prodigy 10 points

Thanks you so much

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TXS0108E:level shifter 5v to 3.3V