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Original question:

LM5022: Isolated DC/DC, audible noise

LM5022: Can multiple output of LM5022 power unit be tied together to increase the output current?

Kazuya Nakai59
Guru 21505 points
Part Number: LM5022
Other Parts Discussed in Thread: LM5170

  Hello guys,

  One of my customers is considering using LM5022 for their new products.

 They have a queston as the follow.

 Q1. Can multiple output of LM5022 power unit be tied together to increase the output current?

 Also they have power supply develop plan for another project.

 Their power supply spec is the follow.

 Vin=16V (DC)

 Vo=125V

 Io=8A (No isolated)

 Q2. Do you have any solution to suit the spec above?

      If you have any solution, could you please tell me it?

 Your would be much appreciated.

 Best regards,

 Kazuya Nakai. 

  • 0
    TI__Guru* 78060 points
    Hi Kazuya-san,

    Thank you for reaching out. The LM5022 is a current model control, naturally it supports multi devices in parallel. However, you need to do the following:
    (1) Use one LM5022 as the Master, and the other as the slave, by tying the slave's FB pin to GND, and it COMP pin to the master's COMP pin;
    (2) Provide an external clock toe each LM5022 to synchronize their switching to avoid beat frequuency.
    (3) If you want to interleave operation, you should provide 180 degree phase shifted clock signals to each LM5022.

    Thanks,
    Youhao Xi, Applications Engineering
  • 0 in reply to Youhao Xi
    Guru 21505 points
    Hi Youhao,

    Thank you very much for your reply.

    I understood what you said. But the power the customer requested is 125V * 8A = 1kW. I think external MOSFET needs to drive over 60A at least because VIN = 16V. If two LM5022 is used, then each MOSFET needs to drive 30A at least.

    Do you think LM5022 can drive the gate of such MOSFET base on your experience?

    Could you please give me your reply?

    Thank you again and best regards,
    Kazuya Nakai.
  • 0 in reply to Kazuya Nakai59
    TI__Guru* 78060 points
    Hi Kazuya-san,

    1 kW is too much the the LM5022, even two in parallel.

    I would recommend you to consider the LM5170, but use it with diode rectifier, namely only drive the low side MOSFETs but do not use high side. The LM5170 has a very strong driver (5A pk) and it is dual phase. It should support 1kW.

    Thanks,
    Youhao