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PMP20058: How to modify the inpurt voltage design?

Johnny Kuo27
Prodigy 20 points

Part Number: PMP20058

Dear TI,

After check with PMP20058 , the VIN is from 8V to 18V for input voltage.

The LM5022 has accepted the max 60V input voltage.

How can we do to change the input voltage from max 18V to 20.9V(19V+-10%)?

Thank you so much.

Johnny

  • 0
    TI__Guru 68725 points
    Basically the ref design can directly support your 20.9V. The design has margin to handle this slight input voltage raise.
  • 0 in reply to Youhao Xi
    Prodigy 20 points

    Dear Ti,

    Thanks for helping. One more question, can we change the output voltage from 54V to 57V?

    How to do it?

    Please refer to your PMP20058's schematic.

    1.If we need to change the transformer(T1), how to define the IPK?

    2. There is 174K(R11) of LM5022's RT,What is the LM5022's switching frequence?

    Thank you.

    Johnny

  • 0 in reply to Johnny Kuo27
    TI__Guru 68725 points
    Hi Johnny,

    First, I do not recommend to directly use the PMP20058 to produce 57V output, unless you remove D1. It is because D1 feeds VCC pin, and its abs max rating is 14V. If you simply raise Vout by reducing R15, the winding voltage for VCC also increases, and it may damage the VCC pin.

    Once D1 is removed, you can reduce R15 to raise the output voltage to 57V. Note that this may increase the power dissipation of the IC because the internal LDO (VCC regulator) supplies VCC. So, pay attention to IC temp rise.

    If you changes the transformer, you can use the same type but add 2 more turn to the secondary winding, making it 14T, and keep the other winding the same. In this way, D1 can stay and the IC internal power dissipation can be reduced.

    Regarding RT, please note that you should carefully read our datasheet. Equation (1) on page 12 determines the frequency setting. For this case, it is 100kHz typical.

    Thanks,
    Youhao