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LM27403: Powering Arria10 10AS066

Peter Jancso
Intellectual 310 points
Part Number: LM27403
Other Parts Discussed in Thread: TPS53119

I am looking for a candidate for switching regulator, that I can power core voltage (0.9V) of Arria 10 FPGA with. 

After added necessary parameters (ext sync, etc), Webench recommended LM27403. Although it meets most of 

the requirements Altera/Intel specified, seems like load regulation is out of limit. 

According to PDN tool of Intel load regulation of 5% is accepted (45mV), however Webench simulation indicates almost 

60 mV overshoot during. Due to other design constraints, i need to use 625 kHz switching frequency. 

Is it possible to tweak on the load regulation or it would be preferable to use other regulator?

Thank you for your answer in advance. 

Best regards, 

Peter Jancso

  • 0
    TI__Expert 5910 points

    Peter,

    Load regulation and Transients are 2 different spec conditions. Typically load regulation is inherent to the part and cannot be changed and the LM27403 will meet the load regulation specs. Remote sense feature helps to improve load regulation and is dependent on your board layout. Transients on the other hand can be tailored by the compensation components, output capacitors etc. Choosing a higher crossover frequency and having sufficient capacitors helps to meet the 45mV spec you have. What is the input voltage range you have to design to?

    Regards,

    Mathew

  • 0 in reply to Mathew Jacob1
    Intellectual 310 points

    Matthew, 

    Thank you for the prompt answer. 

    Yes, I realized I mixed things up a bit. Altera specifies line regulation < 0.4 % and load regulation < 1.2 %, but I see, that LM27403 fulfills both.

    Regarding to transient response, 5% is specified in case of 50% load change. I estimate approximately maximum 22 A current consumption.

    The input voltage is 10 V.

    Best regards, 

    Peter

  • 0 in reply to Peter Jancso
    TI__Expert 5910 points

    Peter,

    That translates to 45mV for transient budget. It is not much so careful design considerations can be followed. You can see an example in Fig 16 of the datasheet.

    Another part that is also well suited to good load transient response is the DCAP architecture, see example TPS53119 again Fig 16 in datasheet shows the transient performance and you can see how the transient u/s or o/s is lower.

    Regards,

    Mathew

  • 0 in reply to Mathew Jacob1
    Intellectual 310 points

    Thank you, Matthew. 

    TPS53119 does not suit to my requirements, I need frequency synchronization. I am going to stick with LM27403.

    Regards, 

    Peter