TPS54824: TPS54824RNVR

Bhadresh Patel

Part Number: TPS54824

We are planning to use below part in our design but meanwhile also we are checked simulation in TINA but in AC simulation we are not able to seen correct result so please help to get the resolve this issue.

TPS54824RNVR

Also I want to know why added this marked component and what is the calculation behind this.

over 4 years ago

0 Anthony F over 4 years ago

TI__Mastermind 35165 points

Hello,

Linj is there to break the feedback loop. The value is very large so that only DC is passed and only AC is blocked in the frequency range of interest.

Cinj is there to AC couple VAC. The value is very large so that only AC is passed and DC is blocked in the frequency range of interest.

Could you give some more details on the incorrect result you are seeing?

0 Bhadresh Patel over 4 years ago

Prodigy 90 points

Hi Anthony,

Do we need this both value for AC analysis purpose or in design also need this value please clarify this things.

0 Bhadresh Patel over 4 years ago

Prodigy 90 points

Hi Anthony,

AC Transfer characteristics coming like this but we are confuse in Phase margin bode plot not going to 180 degree so how to calculate Gain margin.

Gain margin - when phase margin passes through -180 degree that time whatever gain is called gain margin.

As per this definition this attached bode plot not meet the requirement.

0 Ruby Li over 4 years ago in reply to Bhadresh Patel

TI__Expert 7520 points

Anthony is looking into this and will feedback to you soon.

Ruby

0 Anthony F over 4 years ago in reply to Bhadresh Patel

TI__Mastermind 35165 points

Rinj and Linj are just needed to simulate the bode plot in TINA. They aren't needed for the real design.

The Bode plot you shared is normal. In this simulation the phase is shifted up by 180 degrees so the gain margin is the point at which the phase reaches 0 degrees, not -180 degrees. I can't tell the exact numbers with the scale on the y axis but in this plot the phase margin looks to be ~80 degrees and the gain margin ~20 dB.

0 Bhadresh Patel over 4 years ago in reply to Bhadresh Patel

Prodigy 90 points

Hi Anthony,

We have tried through Pspice average model but some error coming while simulation run so please find below attached simulation file and image.

0 Bhadresh Patel over 4 years ago in reply to Bhadresh Patel

Prodigy 90 points

Hi Anthony,

I want to know how to set gain margin measurement in pspice

Actually in phase margin there is showing some mathematical coordinates so can you tell me which coordinates use for gain margin??

I have yellow marked area for phase margin coordinates.

0 Gerold Dhanabalan - Online Design Tools over 4 years ago in reply to Bhadresh Patel

TI__Genius 14455 points

Hi Bhadresh

In the image that you shared, there is an expression for GainMargin (1,2) which you can use. Also, if you just put the cursor where the phase crosses zero, that would you be your Gain Margin.

Regards,

Gerold

0 Bhadresh Patel over 4 years ago in reply to Gerold Dhanabalan - Online Design Tools

Prodigy 90 points

Thanks Gerold,

Actully we need to axis information keep in this Gainmargin(1,2) but i don't know what need to mention in this (1,2) coordinates like in phase margin mention Phasemargin(db(v(vout)),P(v(vout)))-180.

same equation we need for gain margin .

0 Lishuang Zhao over 4 years ago in reply to Bhadresh Patel

TI__Expert 7500 points

Hi,

Gerold and Anthony will feedback to you soon.

Thanks,

Lishuang

0 Gerold Dhanabalan - Online Design Tools over 4 years ago in reply to Lishuang Zhao

TI__Genius 14455 points

Hi Bhadresh

Please try Gainmargin(db(v(vout)),P(v(vout))

Regards,

Gerold

0 Bhadresh Patel over 4 years ago in reply to Gerold Dhanabalan - Online Design Tools

Prodigy 90 points

Hi Gerold ,

I have already try it but its not work actually its showing error like evaluation failed.

0 Ruby Li over 4 years ago in reply to Bhadresh Patel

TI__Expert 7520 points

Hi Bhadresh

Gerold is looking into this and will feedback to you soon.

Ruby

0 Anthony F over 4 years ago in reply to Bhadresh Patel

TI__Mastermind 35165 points

Hi Bradresh,

It seems PSPICE measures gain margin using when the phase hits -180°. So, to get the gain margin you need to subtract 180 from the phase. The following measurement should work.

GainMargin(P(V(VOUT))-180, DB(V(VOUT)))

0 Bhadresh Patel over 4 years ago in reply to Anthony F

Prodigy 90 points

Hi Anthony ,

I have try it but this one also not work.

0 Anthony F over 4 years ago in reply to Bhadresh Patel

TI__Mastermind 35165 points

Is the phase in your simulation dropping to 0 degrees? Can you share an image of the resulting graph from your PSPICE simulation?

0 Bhadresh Patel over 4 years ago in reply to Anthony F

Prodigy 90 points

Thanks Anthony,

Please find below attached simulation file and image and let us know if any thing require but provide solution ASAP.

AC.dat

0 Anthony F over 4 years ago in reply to Bhadresh Patel

TI__Mastermind 35165 points

Hi Bradesh,

The measurement I put in my previous e-mail should work as the phase curve is dropping to 0d. If you are still having issues with the automatic measurements, you could just use cursors to get the gain margin. It may be an issue related to your PSPICE setup and I'm not sure I can help solve that.

Pasting the measurement that works for me again below.

GainMargin(P(V(VOUT))-180, DB(V(VOUT)))

+1 Bhadresh Patel over 4 years ago in reply to Anthony F

Prodigy 90 points

Hi Anthony,

Now this equation work for TPS4318 there is some setting in PSPICE Tool which we have done.

Power management

Power management forum

TPS54824: TPS54824RNVR