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TPS53355: About maximum value of output current

Part Number: TPS53355
Other Parts Discussed in Thread: TPS543B20, TPS549D22, TPS543C20, TPS548D22

Hi,

Let me talk about the maximum value of TPS53355 output current.
Customer use TPS53355 as the power supply for FPGA.
In evaluating the software of FPGA, the current became larger than assumed.
In that situation, I got two questions from customer.

1.Please tell me the risks of 36A of current and the output.
  Customer understand the risk of package temperature (Tj).
  Could you advise about other risks?

2.Is there a possibility of applying current protection other than Rtirp's current limit?
 I understand that the overcurrent protection function can be set higher than 30A.

Customers are using TPS53355 following conditions.
※They plan to reduce the output current when mass-producing.

・Vin=12V
・Vout=0.95V
・Iout(typ)=36A
(Peak current is 38.8A to 43.2A)
・Inductor:0.36uH

Could tell me about all the risks when outputting current exceeding 30 A including the specifications of internal FET etc.

Best Regards,
Yusuke/Japan Disty

  • I would not recommend exceeding 30 A in normal operation. Yes you can set the current limit above 30 A, but that is intended to protect against fault conditions.

    You could probably design some external current limit function using a sense resistor and an external current sense amplifier. But why not select a converter that is rated for your desired current? Maybe TPS549D22 or a stackable converter such as TPS543B20?
  • John-san,

    Thank you for your response.
    I introduced TPS548D22/TPS549D22 and TPS543C20 to customers.
    However,
    When the software evaluation of the FPGA is completed, the current value becomes small.
    (They plan to reduce the output current when mass-producing)
    Therefore, customers want to keep using TPS53355.

    Could you give me advice on the following questions?

    1.Please tell me the risks of 36A of current and the output.
      Customer understand the risk of package temperature (Tj).
      Could you advise about other risks?

    I appreciate that this may be a difficult request.
    But, I want to tell the risk in the case of Iout=36A to the customer.

    Best Regards,
    Yusuke/Japan Disty

  • There are probably significant risks to long term reliability. If this is prototype only, then they may not care if the IC has to be replaced occasionally. Let me see if I can find out more info. It may be a week or so as I will be out of the office for a few days.
  • John-san,

    Thank you for your kind support.
    I can not find reasons that  "can not use more than 30A" in datasheet.
    I want to inform customers about their points of note.
    I will be waiting for your reply.

    Best Regards,
    Yusuke/Japan Disty

  • As noted above, I will be out of the office until Thursday.  I'll let you know then what I can find out.

  • There are two primary issues. Thermal performance and over voltage. With large current you may have excessive switch node ringing both overshoot above VIN and undershoot below GND. You will have to check it for your individual condition. Both depend greatly on PCB layout.