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LM2737: Why the 20A output current limit liste on the product webpage?

Ken Guru
Prodigy 30 points
Part Number: LM2737

Hi everybody,

In the product  webpage of the LM2737 ( http://www.ti.com/product/LM2737/description#parametrics )  there is a value of I_out(max) = 20A listed. Why is that? I can't find this information in the datasheet and I don't understand why there should be a current limit in the first place: This controller has external switches, so the load current doesn't flow through the device, so no Joule heating should occur.

Thanks in advance for any hints,

Cheers,

Ken

  • 0
    TI__Expert 5900 points
    Ken,

    Historically single phase parts were deemed to be capable of 20A. Hence we had these listings in product web page. It does not mean the part is limited to 20A like you point out. As long as the right fets are used and thermal management practices are followed. With that being said the gate drive strengths also play a part. This part has 3ohms so it obviously would not be as efficient driving a high current fet compared to a part with say 1.5ohms gate driver. Low gate driver resistance means higher current to turn on the FET, meaning faster transition times/meaning lower switching losses.

    Regards,
    Mathew
  • 0 in reply to Mathew Jacob1
    Prodigy 30 points
    Hi Matthew,

    Thank you for your prompt reply, that clarified the 20 A limit on the webpage.

    I have one more question: Would you use this controller for a converter with 120 A output current (assuming that the FETs are well dimensioned and properly thermally managed)? If not, what would you recommend?

    Background to our application: We need to implement a controlled current source delivering up to 120 A to heat an electrode. Input voltage is 24 V DC, the output voltage doesn't matter as long as we can deliver the 120 A.

    Cheers and many thanks in advance.
    Ken
  • 0 in reply to Ken Guru
    TI__Expert 5900 points

    Ken,

    I think a controller is the way to go for 120A. However please look for a multiphase controller for an effective design. A 4 phase controller would be good.

    Regards,

    Mathew

  • 0 in reply to Mathew Jacob1
    Prodigy 30 points
    Thanks Matthew, that was very helpful :)