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LM3481: Reference design for customer's system

na na78
Guru 16770 points
Part Number: LM3481
Other Parts Discussed in Thread: PMP20183, LM3478, PMP20182


Hi

Our customer is considering LM3481 to make input boost for 200Vout.
We found PMP20183 reference design and it has seemed to be suitable for our considering system.

The required input range of ours is 9V to 27V but the reference's 9V to 15V.

So, we had following question.

Can you offer reference design (schematics) that is coverring our requirement?

Requirement:
INPUT 9V-27V
OUTPUT 200V/10mA

Or, do you have other solution that is coverring our requirement?

We want to refer it and make the custom board.

BestRegards

  • 0
    TI__Guru* 76325 points
    LM3481 cannot support 9Vin to 200Vout. Its duty cycle is limited to 85% and you need 96% to establish the 200Vout. Suggest to consider LM3478, and use TI online tool Webench to help you design.

    Best Regards,
    Youhao Xi, System and Applications Engineering, APP-BMC-BCS, TI
  • 0 in reply to Youhao Xi
    Guru 16770 points
    Hi

    Thank you for your reply.

    Actually, LM3481 is limited by duty cycle capability.
    However, PMP20183 offers Vin=9V and Vout=200V.

    I think the output voltage is multiplied by 3 using charge pump circuit. Is my understanding correct?

    200V/3 ≒ 67V,
    (67V-9V)/67V = 86% (near LM3481 duty cycle limit)

    The switching frequency of PMP20182 would be ~100KHz because Rfa = 215K is selected.

    Reducing switching frequency, I think PMP20183 with LM3481 can support our requirement.
    If you have concern, please tell us.

    I used TI's Webench to make our design but it didn't make 9Vin to 200Vout solution.

    BestRegards
  • 0 in reply to na na78
    TI__Guru* 76325 points
    Yes you are right the PMP20183 can be used for your application. You can reduce the switching frequency slightly, as the datasheet recommends 100kHz min. There is some margin there but please do not use a too low frequency. Please download the schematic from the TI webpage under PMP20183. Thanks.
  • 0 in reply to Youhao Xi
    Guru 16770 points
    Hi Youhao

    Thank you for your reply.

    Then let me back to my first question.

    PMP20183 offers different input range from our request.

    Requirement: INPUT 9V-27V
    PMP20183:9V-15V

    Regarding to PMP20183, what part should we modify to meet input 9V-27V?

    BestRegards
  • 0 in reply to na na78
    TI__Guru* 76325 points

    Thank you!  I checked the PMP20183 schematic and most parts are fine except two:  C2 and L1.  You need to replace C2 with a 50V ceramic capacitor, and L1 with a >1.6A Isat inductor. 

    Best Regards,

    Youhao Xi, System and Applications Engineering, APP-BMC-BCS, TI