Author Topic: TXS0104ED translator is not generating 5V PWM from 3.3V PWM from MCU ?  (Read 436 times)

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Offline muthukural001

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Hello All,

I have been working on controlling a motor using PWM which is from microcontroller (3.3V logic)...Since the motor driver that I am using is 5V, I used a level translator that converts 3.3V signals of microcontroller to 5V signals that is Motor driver compatible...The problem is that the PWM signal level at the level translator output around 3.2 V instead 5V...Is it due to  the weak current source of that channel and it is reducing the voltage level...Do I need an external pull-up at the output ?...But, I have not checked the PWM level without motor driver yet to confirm the above...Do anyone think this problem is related to others?

Thanks,
 

Offline fchk

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You should not use bidirectional level translators with automatic direction control unless you REALLY need to. The automatic direction control is easy to disturb, and the push capability is usually low.

74LVC1T45/2T45/8T245 are much more reliable and have +-24mA drive capability.
 

Offline SiliconWizard

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Yeah, I usually don't like those much either.

That said, the datasheet (which isn't that great IMO) states: "An external pull down resistor decreases the output V OH and V OL ."

Check that your motor driver doesn't load the outputs of the translator too much. Have you looked at the outputs with the motor driver disconnected?
 

Offline muthukural001

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Hi,

Thanks for the reply...Actually, the purchased motor driver board has 10K pull down resistor at its pwm input...It makes a voltage divider with the 10K pull up resistor inside the translator chip...So, the voltage divides half...After removing the 10K, I can see the PWM at 5V...


Thanks,
Muthu
 


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