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LM25575 inverting design - where to connect exposed pad?

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Replies: 5

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We use LM25575 in an inverting design to generate -11V from 12V input.

The webench design doesn't show where to connect the exposed pad (EP).

Where should EP pin connected to GND or Vout (-11V in our case)?

Or we could connected to either of them because it doesn't matter (is not internally connected to the die)?

We would prefer to be able to connect it to board GND as that is the plane we have a lot of copper on.

Thanks,

Valentin

  • Hi Valentin,

    The EP needs to connnect to GND.

    Regards,

    Howard

  • In reply to Howard Chen-WEBENCH Design Center:

    Thanks Howard for your quick response.
    In this document: www.ti.com/.../snva425a.pdf at page 4 it shows EP connected to -Vout.
    Is LM255575 different than LMZ14203 that is shown in the above document?
    Also in this thread e2e.ti.com/.../347100 in the initial post there is an attached schematic showing LM25575 used to generate a positive and negative output voltage.
    For the negative output voltage EP pin is connected to -Vout.
    Does it matter if EP is connected to GND or -Vout? Just want to make sure will work if we connect it to GND for negative output.
    Valentin
  • In reply to Valentin Popa:

    Hi Valentin,
    Sorry, what I meant was to connect the EP like the A/PGND pins to -Vout.

    Regards,

    Howard

  • In reply to Valentin Popa:

    Valentin,

    Both you and Howard are correct. Let me explain:
    There are two GND to consider. System GND and IC GND. They are different in the inverting application of a Buck.
    Howard was talking about IC GND, and you are talking about system GND.

    For your purposes, please connect Exposed pad, IC GND and Analog GND to -Vout.
    Please connect the inductor output to System GND.

    For more information please refer App note SNVA722B - Inverting Made Simple.

    It explains with formulas, diagrams and schematics how to construct an inverting application.

    Thanks,
    Anston
  • In reply to Anston Lobo:

    Everything is clear now. Thanks Howard and Anston.
    Valentin

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