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LMH3401: TINA simulation

Kailyn Chen
Genius 9560 points
Part Number: LMH3401

Dear;

 When I use split power supply of LMH3401, and I wonder why the output is not correct. But single power supply has no problem. Please help to check. Thank you very much.

2061.LMH3401 split supply.TSC

Best regards

Kailyn

  • 0
    TI__Genius 14036 points
    Hi Kailyn,

    When you switch to split supply, do you also change the power down pin to VEE?

    Best regards,

    Sean
  • 0
    TI__Genius 13935 points
    Hello Kailyn,

    I confirmed Sean's advice. Connect the PD pin to Vee or let it float and the amplifier will be active. Otherwise the amplifier is in the powered down state. On the actual amplifier there is a ground reference pin that can be used to set the reference level for the PD pin. The ground pin was not included on the TINA model, so on the TINA model the PD pin is referenced to Vee by default.

    Regards,
    Loren
  • 0 in reply to Loren Siebert 1
    TI__Genius 9560 points

    Dear Loren and Sean,

    Thank you very much for your reply, and I changed the PD pin to VEE before and found that it could work normally, but the datasheet

    describes that PD<0.9V would be active, so I need confirm either the model or the datasheet has something wrong. Now I understand.

    Thanks again.

    Best regards

    Kailyn

  • 0 in reply to Kailyn Chen
    TI__Genius 13935 points

    Hello Kailyn,

    You have identified a weakness in the model.  The LMH3401 device has a ground pin.  The PD pin threshold is 0.9V above the voltage you apply to the ground pin.  The model does not have this pin, so the PD pin is referenced to the Vee pin instead. 

    This amplifier is somewhat unique as most FDA amplifiers have no ground pin.  What is also unique is that the ground pin has no function with regard to the signal path, it is a digital reference only, so we did not think it was a big issue to leave it out from the model. 

    I hope this answers your questions.  I will get an email if you post additional questions to this thread so feel free to post any additional questions. 

    Regards,

    Loren