TPS92602-Q1: Calculating Loop Compensation

Andreas Lindner

Part Number: TPS92602-Q1

Hello,

I'm having difficulties to calculate the loop compensation for my application and also the provided example from the equations given in the datasheet.

Could you please provide a detailed calculation for Rcomp, Ccomp and C6 (equations (39) to (45) in datasheet), showing the values used and explained where do they come from?

Further, I don't see in equation (30) from where the 9mV for Vvout-ripple is taken. Could you please explain this?

More generally spoken, it would be really helpful, if there would be an Excel sheet for calculating an application circuit...

Thanks for any help in advance!

over 7 years ago

0 Shirley He over 7 years ago

TI__Expert 5475 points

Hi,

The equations in the datasheet are just general equations to calculate the boost regulator. In fact, sometimes it is not easy to get a good compensation value from these equations due to some nonideal factors. And I'm sorry we do not have any excel sheet for the calculation. But based on our experience, we can always get a good loop stability result by using the compensation values in our datasheet and EVM. You can start by using these values and make small modifications according to the test if needed.

0 Andreas Lindner over 7 years ago in reply to Shirley He

Intellectual 420 points

Hi,
thanks for your answer, but my issue is that I'm getting totally wrong values. Most likely because I misunderstood something, probably there is a typo in the formulas. It would help me a lot if the datasheets example calculations would show the used values.

Best Regards,
Andreas

0 Shirley He over 7 years ago in reply to Andreas Lindner

TI__Expert 5475 points

Hi,

Sorry we do not have the spreadsheet for the example calculation at present. Which specific parameter in the equations is not clear to you? Could you please use the recommended values first to see if it works? Thanks.

0 Andreas Lindner over 7 years ago in reply to Shirley He

Intellectual 420 points

Hi,

in this case I can't run a try and error strategy, I really need to calculate values first.

I'm just working on a simple spreadsheet, please find it attached. Please have a look at line 62 in the document, this is the calculation of equation (43). The result is not plausible to me.

Best Regards,

Andreas

https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/196/TPS9260x.7z

0 Andreas Lindner over 7 years ago in reply to Andreas Lindner

Intellectual 420 points

Can somebody please look into this?

0 Shirley He over 7 years ago in reply to Andreas Lindner

TI__Expert 5475 points

Hi Andreas,

Could you please send me the excel file that contains the equations that you use? I'm not able to see the equations when I open the file.

0 Andreas Lindner over 7 years ago in reply to Shirley He

Intellectual 420 points

Hi Shirley,

the file I attached before was in Open Document format, however I attach it here again as Excel file.

Best Regards,

Andreas

TPS9260x.xlsx

0 Shirley He over 7 years ago in reply to Andreas Lindner

TI__Expert 5475 points

Hi Andreas,

Thanks for sharing the file. Please allow me some time to look at the equations. I'll get back to you soon.

0 Andreas Lindner over 7 years ago in reply to Shirley He

Intellectual 420 points

Hi Shirley,

any news here?

Best Regards,

Andreas

0 Shirley He over 7 years ago in reply to Andreas Lindner

TI__Expert 5475 points

Hi Andreas,

Sorry for the late reply. I checked your file and corrected the mistakes as attached. One mistake is the conversion ratio from uF to F and from uH to H should be 0.000001, not 0.00001. Another is the Gm in Equation 43 should be 0.001, not 1000. Sorry for the typo in the datasheet. We will update the datasheet later.

After the modification, according to the calculation, Rcomp is 19.6 ohm. It is still a little bit small due to the small dynamic resistance Rled in the file, which is 0.2ohm. The dynamic resistance of an LED is usually higher than that. You can check and update accordingly.

5873.TPS9260x.xlsx

Please help to click "Resolved" if you think this solved your question. Thanks a lot.

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TPS92602-Q1: Calculating Loop Compensation