TPS7A30: Can you confirm the part number for L19 and tell me how the circuit is supposed to work?

Viraj Adam

Part Number: TPS7A30
Other Parts Discussed in Thread: DAC7760, TIPD167, TPS54060

My task is to get +10V and -10V for DAC7760. I came across above similar circuit from one of TI documents.

Can you confirm the part number for L19=744870471. The datasheet for it shows that its a common mode choke only. But it is supposed to be fly buck transformer.(Primary and secondary inverse).

When I implemented above circuit using common mode choke, it's not generating the negative power supply across C199.

Attached herewith is schematic I am trying to implement.DUAL POWER SUPPLY GENERATION.pdf

Let me know if you have any other simple circuitry or suggestions.

Thank you!

over 6 years ago

0 Ryan Eslinger over 6 years ago

TI__Guru 55940 points

Hi Viraj,

It looks like you are basing your design on TIPD167. When Comparing your schematic to this TI Design, I noticed that you do not appear to have a source or net tie on your negative rail. Please note that in the TI Design, the GND pin of TPS54060 is tied to the negative rail rather than GND.

Also in your schematic I believe that the polarity for C199 should be flipped.

Very Respectfully,

Ryan

0 Viraj Adam over 6 years ago in reply to Ryan Eslinger

Prodigy 85 points

Hi Ryan,

Thank you very much for the quick response and sharing relative documents.
I have rectified the mistake.

I will be implementing above similar design given by you.
Can you please tell me if its okay to use the above circuit for Analog section?

0 Viraj Adam over 6 years ago in reply to Viraj Adam

Prodigy 85 points

If possible, can you elaborate the working of the circuit?

0 JohnTucker over 6 years ago in reply to Viraj Adam

TI__Guru**** 191445 points

Viraj,

That design is not a fly buck design. Rather it uses a coupled inductor to generate a positive rail along with a negative rail in an inverting buck-boost topology. Here is a reference document that explains the circuit:
www.ti.com/.../slva369a.pdf

0 Viraj Adam over 6 years ago in reply to JohnTucker

Prodigy 85 points

Hi John,

Thank you very much for sharing the docuement.
It really helped me.

Thanks.

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TPS7A30: Can you confirm the part number for L19 and tell me how the circuit is supposed to work?