UCC28070: Voltage loop Compensation/Configuration

ld14

Part Number: UCC28070

Hello,

I did find the formula used on the calculation of Zo is different in the Datasheet SLUS794F than in the application report SLUA479B.

1. In the application report, the ripple voltage is calculated using 2*Pin. The ripple voltage formula is then used in the calculation for Zo. While in the datasheet there is a reference to a 0 to Peak ripple voltage, where only Pin is used in the ripple calculation, then this formula is used to calculate Zo. There is a factor 2 missing.

2. In the datasheet is mentioned the amount of k3rd third harmonic content, while in the application report is not mentioned at all.

Could you please help me with some clarification about this?

Thank you

over 3 years ago

0 Yunsheng Qu over 3 years ago

TI__Genius 9790 points

Thanks for your interest in TI here. I've contacted the appropriate product group. You should hear from them soon.

0 David Huang33 over 3 years ago in reply to Yunsheng Qu

TI__Genius 9140 points

Hello,

Please follow the application note SLUA479B , the ripple formula is correct.

So this is a mistake in the datasheet SLUS794F.

For the voltage loop design, I would also suggest customer can follow SLUA479B.

Sorry about the mistake.

0 ld14 over 3 years ago in reply to David Huang33

Prodigy 50 points

Hello,

Thank you for your answer. What about the K3rd coefficient. Could you please clarify how to use this one?

The datasheet does mention how to design the voltage loop based on this coefficient. In the application report this is not mentioned.

Could you please provide some more information about this?

Thank you

0 David Huang33 over 3 years ago in reply to ld14

TI__Genius 9140 points

In the application note, it suppose 1.5% of 3rd- harmonic input distortion allowable.

you can refer to datasheet page 26 about the calculation on Krd.

1% of 3rd-harmonic refers to 3.2V*2%.

1.5% of 3rd-harmonic refers to 3.2V*3%.

hope this is clear.

0 ld14 over 3 years ago in reply to David Huang33

Prodigy 50 points

Hi,

Thank you for your clarification on K3rd coefficient.

Just to complete the section, The Z_OV formula at page 27 of the Datasheet is missing just the factor 2 at the denominator (2*Pin) from the Vripple formula.

Is that correct?

0 David Huang33 over 3 years ago in reply to ld14

TI__Genius 9140 points

yes!

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UCC28070: Voltage loop Compensation/Configuration