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pwm from TL1451A

Gerre Strait
Prodigy 20 points
Other Parts Discussed in Thread: TL1451A

Hello,

 

I'm hoping to use the TL1451A as a simple PWM output, with just a Duty Cycle control.

I wired it up as shown in the Test Circuit from the datasheet, but the output simply remains at 5V (Vcc)

What combination of inputs do I need at Feedback and DTC to vary the Duty Cycle?

Do I also need to change the error-amp inputs?

 

Thanks!

  • 0
    Prodigy 20 points

    So far I have tried grounding FEEDBACK and varying DTC between 1.45V and 2V.

    No change through the pullup.

     

    Then I tried grounding DTC and varying FEEDBACK. 

    Still no change.

     

    I then varied both FEEDBACK and DTC between 1.45V and 2V.

    Again, OUTPUT remained at VCC (5V).

     

    The op-amp is wired + to Vref and - to GND.

     

    Do I need to change those inputs?

    Is the pullup too strong? (4.7k, as prescribed in the datasheet.)