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LMH3401 PD pin functionality

Alex Chenski
Prodigy 100 points
Other Parts Discussed in Thread: LMH3401

Hello TI community,

I am looking into an application for LMH3401. I have downloaded Tina9 model and test schematics for the device, but I am having trouble with PD pin.

The original schematics (SBOS695) uses a complicated auto-centering two-rail power supply arrangement, but with negative rail set to zero, and positive to +5V.

When I simplified the power rails to plain +-2.5V, the question was how to connect the PD pin to enable amplification.

The datasheet for LMH3401 says that if the PD is "High (> GND + 1.2 V) = low-power (sleep) mode. Low (< GND + 0.9 V) = active."

However connecting PD to GND results in attenuated signal and apparently inactive circuit.

I noticed that  the PD is referenced to VEE (= Vs-) in the reference schematics. If I connect the PD to VS-, the circuit works.

The question: is this an error in the LMH3401 model, or is it a misprint in documentation?

Thanks.

  • 0
    TI__Genius 13935 points
    Hello Alex,

    The TINA model is designed for basic circuit validation and does not have the GND pin, so in the TINA model the PD pin is referenced to VEE.

    In the actual amplifier, the PD pin does not reference to the VEE(Vs-) pin. The PD pin is referenced to the GND pin on the chip (not the ground in your circuit). The PD must be below 1V with respect to the GND pin on the LMH3401.

    If you want the amplifier to mimic the TINA model then tie the GND pin to the most negative power supply. At this time it is not possible to duplicate the amplifier behavior using the TINA model.

    Regards,
    Loren
  • 0 in reply to Loren Siebert 1
    Prodigy 100 points

    Thanks for the clarification, much appreciated.

    -Alex