TPS56520 bode plot measurement when the output voltage is set by register setting

K. Sasaki14

Other Parts Discussed in Thread: TPS56520

Can we measure bode plot of TPS56520 when the output voltage is set by register setting?
Our customer could measure when output voltage is resistor setting. However they could not measure when output voltage is I2C register setting.
Do you have any idea about this cause?
We are understanding this is DCAP2 device. However bode plot result is criteria for stable judgement in our customer.

Best Regards,
Kohei Sasaki

over 8 years ago

0 K. Sasaki14 over 8 years ago

Guru 10200 points

Hi all,

I have not gotten your answer about this post.
Could anyone give me answer?

Best Regards,
Kohei Sasaki

0 JohnTucker over 8 years ago in reply to K. Sasaki14

TI__Guru**** 191445 points

I have not personally tried it, but I cannot think of any reason why it would not work.

0 Eric Guo1 over 8 years ago in reply to JohnTucker

TI__Intellectual 2590 points

You use I2C to adjust the output cap, we have an internal resistor for the feedback, so it should be ok not able for you to test the loop, because your resistor which you connect with the intrument is not in the close loop. this is my view, let me check with the deisgner and then get back to you.

thanks!

0 JohnTucker over 8 years ago in reply to Eric Guo1

TI__Guru**** 191445 points

Actually, the I2C function sets the output of a DAC as the reference and switches the inverting input to the error amplifier from VFB to VOUT. As long as the VOUT pin is included in the loop (50 ohm injection resistor in between the actual output and the VOUT pin) it should work.

0 K. Sasaki14 over 8 years ago in reply to JohnTucker

Guru 10200 points

Thank you for your support.
We confirmed the bode plot measurement is possible with EVM even in I2C control condition.
And I found VOUT pin is connected to actual output in our customer circuit. (top side of injection resistor.) So we judged this cause is due to VOUT pin connection.

Best Regards,
Kohei Sasaki

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TPS56520 bode plot measurement when the output voltage is set by register setting