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TPS55340EVM-148: obtain negative output

Nitish Agrawal
Expert 1525 points
Part Number: TPS55340EVM-148
Other Parts Discussed in Thread: TPS55340,

Hello,

I am considering using TPS55340 to realize a 24V input to -4.2V / 3A continuous output converter.

TPS55340EVM-148 (isolated flyback) has been tested at 24V input to +5V / 2.5A continuous output.

In order to obtain the negative output, I am considering treating the secondary ground as VOUT and connecting the "original" VOUT to primary ground (required in my application).
Does anyone see any issue with doing this (functionally or layout / isolation / noise related)?

If there are better options (cheaper and more efficient) to realize the 24V input to -4.2V / 3A continuous output converter....I am looking at either transformer or "DC isolated" (Ćuk) designs.

Kind regards,

Nitish

p.s. as soon as I entered TPS55340EVM-148 in the part # field, it forced the forum to Non-isolated DC/DC...

  • 0
    TI__Guru 68595 points
    The webench is not set up to create negative flyback output, but since it is isolated, and positive or negative is just a relative to ground reference, then you can do as you mentioned: Vout connects to GND and the output return becomes the negate output rail. Note that the opto couple is still needed, and references to your "negative" output rail as in the original circuit.