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PMP10733: Using the positive Voltage as Feedback reference?

Lukas Jani
Prodigy 190 points

Part Number: PMP10733
Other Parts Discussed in Thread: TPA3251, , PMP22343, TPS54560

Hello all,

i'm designing a supply structure to supply both the TPA3251 VDD as well as the preamplifiers OP-Amps.

Therefore the output requirements of the supply converter structure are: +12V with ~100mA Current, Tolerance Band is 11 - 13V, and an opposing negative voltage at -12V with <50mA current (only OpAmp Supply and Drive, Tolerance only affects opamp output capability, so lets assume -10 .... -15V is OK)

Input Voltage is 10 - 36V, hence using a flybuck is off the table. It seems a stacked buckboost might be a good choice. Similar to the PMP10733 i plan to use a 1:1 coupled inductor (1:1 not 1:1:1!), yet i'm concerend the negtive output voltage is regulated well, but the positive output voltage will not be.

--> The idea overall is to regulate the positive output even with an inverting buckboost. Is there any good idea on how to do that? i do not want to use a post-reg for the +12V due to size and cost constraints.

If there is any other better idea for supply structure, i'm open for it ;)

Thanks,

best regards,

Lukas

  • 0
    TI__Expert 6670 points

    Hi Lukas, sorry for the delay here, the original designer for this supply has left TI. I am asking another engineer to take a look.

  • 0
    TI__Intellectual 1570 points

    Hi Lukas,

    PMP22343 shows another option for regulation. In this design the differential voltage is regulated, then a Zener diode is added to ensure the negative output does not fly down too far. With that wide of an input you will most likely need some form of zener to protect one of the outputs.

    It also helps to use a non-synch buck device so that you can match the diodes. PMP22343 uses TPS54560, which would also make sense for +36 Vin to -12 Vout.

    Let me know if you have any questions on this.

    Thanks,

    John