TPS61288: Phase compensation design

Kaji@PAN

Part Number: TPS61288

Hello,

I am designing phase compensation for the TPS61288 device.
I calculated Rc, Cc, Cp using equations 12,13,14 in the datasheet.
Attach my calculated Excel sheet.
Rc: 648kΩ, Cc: 440pF, Cp: 218pF (VIN = 4.5V)
The GEA value was obtained from the thread below.

However, when I checked with WEBENCH under the same conditions, there is a big difference between my calculation result and WEBENCH calculation result.
The calculation result of WEBENCH is attached.
Rc: 26.7kΩ, Cc: 33nF, Cp: 82pF

What is the difference between the two?

e2e.ti.com/.../tps61288-calculation-of-rc-in-phase-compensation

Best regards,

TPS61288 calculation.xlsx

WEBENCH TPS61288 5V to12V2A.PDF

over 4 years ago

0 Yichen Xu over 4 years ago

TI__Expert 4760 points

Hi Kaji,

One possible reason is that you use nominal value of output capacitance for calculating. And note that WEBENCH only provide a useable parameter setting and it is not optimized so we suggest do the calculation.

0 Kaji@PAN over 4 years ago in reply to Yichen Xu

Mastermind 7840 points

Thank you for your reply.
I calculated with the specifications in Figure 8.1 of the data sheet.
I will attach an excel sheet of the results.
In this case, Rc has a value of about 1MΩ.
Rc in Figure 8.1 is 36.5kΩ.
What is this difference?
For reference, 36.5kΩ is close to the value I calculated with WEBENCH.

Best regards,

TPS61288 calculation Fig8.1.xlsx

+1 Yichen Xu over 4 years ago in reply to Kaji@PAN

TI__Expert 4760 points

Hi Kaji,

I checked your table and you used nominal value of output capacitance for calculating as I mentioned in last reply. You should use effective capacitance which should be much lower than 132uF.

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TPS61288: Phase compensation design