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Original question:

Looking for medium voltage, external FETs, synchronous & capable of sinking current, buck-converter (for TEC / peltier driver...

LM5176: Designing a Compact, Dual TEC Driver with Bi-directional Current

Eric Seger
Prodigy 160 points
Other Parts Discussed in Thread: LM5176, TPS55288, LM51772

Tool/software:

Hello,

I am working on designing a compact, dual TEC driver. The requirements for the TEC driver are as follows:

  • Bi-directional TEC current with 8A continuous
  • TEC Voltage of 15V
  • Input voltage of 24V
  • Controllable switching frequency

I am considering using the LM5176 buck-boost controller as described in application note SNVAA70 (Bidirectional TEC Driver Design for 40-W TEC). Additionally, I am looking at the newer LM51772 buck-boost controller and the more compact TPS55288.

I have a few questions:

  1. Can the LM51772 and TPS55288 controllers sink current and are they suitable as a TEC driver? Are there any limitations when sinking current with these controllers?
  2. More generally, how can I determine if a buck-boost controller can be used to sink current? For example, without SNVAA70, I would not have known that the LM5176 can sink current.

Thank you for your assistance!

  • 0
    TI__Genius 16015 points

    Hi Eric,

    Thanks for reaching out.

    We will look into this and come back with an answer early next week.
    Thanks for your patience.

    Best regards

    Moritz

  • 0 in reply to Moritz
    TI__Guru 58641 points

    Hi Eric,

    sorry for the late reply.

    The LM51772 can also sink current when operating in FPWM mode.

    Basically all 4 switch BuckBoost can sink current when operating in FPWM mode.

    For the TPS55288 I can not give more details as this does not belong to the device we support in our team here.

    In case need just open a new ticket with just that device.

    Best regards,

     Stefan

  • 0 in reply to Stefan Schauer
    Prodigy 160 points

    Hi Stefan,

    Thank you for your response. I appreciate the information about the LM51772's ability to sink current in FPWM mode.

    I have a few more questions regarding the LM51772:

    1. CDC Pin for Monitoring Bidirectional Current: Can the CDC pin be used to monitor bidirectional current?

    2. Limitations When Sinking Current: Are there any inherent limitations or reduced functionality when using the LM51772 to sink current?

    3. General Limitations as a TEC Controller: Are there any other inherent limitations or considerations when using the LM51772 as a TEC controller that I should be aware of?

    Thank you for your assistance!

  • 0 in reply to Eric Seger
    TI__Guru 58641 points

    Hi Eric,

    1.

    yes, you can get positive and negative current in the CDC pin. So also this report:
    Current Monitoring with Positive and Negative Currents on LM5177x Devices (Rev. A)

    The CDC pin of the LM51772 behaves identical.

    For the LM51772 you can also use VCC1 as reference voltage as this provide a very accurate output voltage.

    2. Just consider that your source need to be able to sink the current.

    3. None that I am aware of.

    Best regards,

     Stefan