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UCC27528 Enable Pin Voltage Threshold

Other Parts Discussed in Thread: UCC27528

Hi TI Team I need your help!

I am currently using the UCC27528 within an IGBT gate drive application however I have identified some issues regarding the device enable pin voltage threshold.

The design arrangment is such that both input pins INA and INB are pulled up to VDD and the enable pins ENA and ENB are tied together and connected to an input PWM waveform (Low Level TTL 3.3V). As expected the device outputs the PWM trace given a 3.3V input waveform however when the input waveform voltage is taken to 3.1V the output drops off to 0V. The datasheet states that VEN_H should be 2.1V however it seems to be much higher. Is anybody able to shed any light on why the device exhibits the described operational characteristics?

Thanks in advance …

Luke Ashton

  • Hi Luke,

    To get PWM output, it is recommended to use input pins.

    Generally, EN pin is used to enable or disable the output when there is an abnormal condition detected such as fault.

    May I know what is the frequency, pulse width, rise time, and fall time of PWM signal applied to EN pin?

    The EN input is a Schmitt trigger type. If the overdrive to the input of Schmitt trigger is not large enough or not for sufficient time (if it is too fast), it might not toggle the output. This might be the case you are observing. Would you please confirm the voltage by taking waveform at the driver EN pin at 1V/div or lower?

    I will be able to help you more, if you could share more information and waveforms, if possible.

    I sincerely appreciate you taking time to discuss the issue with us and hope that this description helps you solve your design problem.

    Thanks and regards,