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TL2844B: VCC waveform and pin 6 output waveform are abnormal

Annie Liu
Genius 10295 points
Part Number: TL2844B


Hi Team,

pin 6 output waveform

VCC waveform

The customer wonders what might be related?

Regards,

Annie

  • 0
    TI__Mastermind 33115 points

    Annie,

    The VCC waveform looks to be hitting the the start threshold voltage you marked with curser H2 (16.6V) but then the VCC is falling below the minimum operating voltage after start-up and you marked this with curser H1 (10.1V). You have until the time the VCC voltage falls from 16V (turn-on) down to 10V (turn-off) to provide a regulated bias voltage to the VCC that is >9V. This is typically done with a bootstrap winding from the transformer to the VCC pin. The pin 6 output voltage tries to start-up but following the VCC voltage in a patter of ON-OFF-ON-OFF-REPEAT.

    Regards,

    Steve