TPS2549-Q1: Phase Margin of DC/DC

tateo yamashiro

Part Number: TPS2549-Q1

Hi,

We got a question from customer about TPS2549-Q1.
Could you help us?

[Question]
How is the way to measure phase margin of DC/DC? I would like to make sure right connection to FRA. There is Loop pin(TP9) on EVM(-729). Is the below figure right?

Best Regards,
tateo

over 7 years ago

0 Eric Wright over 7 years ago

TI__Mastermind 42795 points

We have some material discussing this. I am trying to locate it and will get back with you.

0 Eric Wright over 7 years ago in reply to Eric Wright

TI__Mastermind 42795 points

You can perform the measurement as shown below.

0 tateo yamashiro over 7 years ago in reply to Eric Wright

Guru 10890 points

Thank you for your support.

We measured phase margin the way you kindly told us. We can see there is peak at 100kHz. Can you think of anything that might have caused it?

Best Regards,
tateo

0 Eric Wright over 7 years ago in reply to tateo yamashiro

TI__Mastermind 42795 points

Did you use the TI EVM for this test? If you used another board, please send the schematic.

We have internal test data up to 100kHz but I don't see this effect in those plots.

As an FYI, if you used the TI EVM we recently made a change to replace L2 (ferrite bead) with a zero ohm resistor. It is possible that the EVM you have might still have the ferrite bead installed (depending on when you acquired the EVM). Replace the ferrite bead with a zero ohm resistor if this is the case.

0 tateo yamashiro over 7 years ago in reply to Eric Wright

Guru 10890 points

We found problem with connecting the board and load. We improved connection and measured phase margin again. This result we got better plot.
Thank you for your support!

Iout=2.4A

Best Regards,
tateo

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TPS2549-Q1: Phase Margin of DC/DC