UCD90320: Margin

user6158403

Part Number: UCD90320
Other Parts Discussed in Thread: TPS62090-Q1,

Hi,

When I not enable margin pin, then the voltage is stable.

When I enable margin pin to control the voltage, then I use equipment to measure to waveform, then voltage is unstable(voltage is tingle). Is phenomenon is normal?

If this phenomenon is abnormal, how can I avoid this problem?

First picture is not enable margin.

Second picture is enable margin.

over 4 years ago

0 yihe over 4 years ago

TI__Guru 66230 points

Hello

In order to test margining function, you have to design a related circuit based on https://www.ti.com/lit/pdf/slva845 and https://www.ti.com/lit/zip/slvc676.

Do you have these circuit right?

Regards

Yihe

0 user6158403 over 4 years ago in reply to yihe

Intellectual 280 points

Yes, I use margin to adjust +5% or -5%. The voltage is ok, but voltage is tingle.

I don't understand why this phenomenon occur.

0 yihe over 4 years ago in reply to user6158403

TI__Guru 66230 points

Hello

Have you read the two links shared in the previous post? Is the R3/R4 and C1 calculated based on the design?

I do not think you can set the duty cycle to 100%。 The initial duty must be set to Vref - Vol/(Voh-Vol), section 2.6 of the design guide.

Regards

Yihe

0 user6158403 over 4 years ago in reply to yihe

Intellectual 280 points

Is the R3/R4 and C1 calculated based on the design? yes

The initial duty must be set to(Vref - Vol/)(Voh-Vol), section 2.6 of the design guide.

After I cofigure 100%->25% for (Vref - Vol/)(Voh-Vol), voltage still tingle.

0 yihe over 4 years ago in reply to user6158403

TI__Guru 66230 points

Hello

Could you share your schematics and project file?

Regards

Yihe

0 user6158403 over 4 years ago in reply to yihe

Intellectual 280 points

I give you schematics and project file for P1V15_BMC part.

Please help me for this voltage. Thanks.UCD.rar

0 yihe over 4 years ago in reply to user6158403

TI__Guru 66230 points

Do you see the similar issue on other margining rail other this BMC1V15?

The principal of the margin is to adjust the FB voltage to adjust the output voltage accordingly. Have your checked whether TPS62090-Q1 allow adjust FB voltage externally?

if you do not set the margin mode to active-trim, instead, set it to tri-state, when you turn margin high or low, does the voltage follow accordingly?

Regards

Yihe

0 user6158403 over 4 years ago in reply to yihe

Intellectual 280 points

Do you see the similar issue on other margining rail other this BMC1V15? All margin voltage will tingle.

Have your checked whether TPS62090-Q1 allow adjust FB voltage externally? yes.

if you do not set the margin mode to active-trim, instead, set it to tri-state, when you turn margin high or low, does the voltage follow accordingly?

When I set to tri-state mode, voltage still tingle.

0 yihe over 4 years ago in reply to user6158403

TI__Guru 66230 points

Could you provide zoom in picture? 1s division is too large to see the detail? is this waveform from margin high or margin low? Could you also provide the PMW output signal as well?

One time is to reduce the frequency or increase the C1 cap to 10x to see whether you get a better case?

Regards

Yihe

0 user6158403 over 4 years ago in reply to yihe

Intellectual 280 points

One time is to reduce the frequency or increase the C1 cap to 10x to see whether you get a better case?

Both method do not solve the problem, voltage still tingle.

I think PWM is causing this problem, because only I open margin that caused this problem.

UCD_.rar

0 yihe over 4 years ago in reply to user6158403

TI__Guru 66230 points

Hello

Why the waveform have so many glitches? If the voltage into the UCD90320 have so many glitches, it will impact the margining. via checking your schematics, I do not see any decoupling filter on the MONx pins, we recommend a 10nF-100nF cap on the MON to filter glitches. Could you add the filter? also, please make sure that the V33A does not have glitch as well since the glitches on the V33A will impact the ADC accuracy.

Regards

Yihe

Power management

Power management forum

UCD90320: Margin