WEBENCH® Tools/TPS53315: ripple injection circuit

ADARSHA A N

Prodigy 245 points

Part Number: TPS53315

Tool/software: WEBENCH® Design Tools

hi,

i have shared my WEBENCH design below

https://webench.ti.com/appinfo/webench/scripts/SDP.cgi?ID=8E9069BE200976FA

OUTPUT -5V , INPUT -12V, OUTPUT CURRENT -11A, FSW 500KHz

in my ckt

L1- XAL7070-182MEB (SAME)

Cout ( Ceramic cap) : - 100uF 16V 1210 20 % X5R( qty 4)

47uF 16V 1206 20 % X5R( qty 4)

Total de-rated capacitance :- approximately 287uF

could you please check the ripple injection and feedback network is okay?

In the datasheet less than 50mV target is mentioned for VINJ_SW, but there is no recommendation for VINJ_OUT.

is there any limit consideration for VINJ_OUT.?

And also while Calculating VINJ_OUT should we need to use de-rated Cout value or total Cout?

could please verify Rr, cr, Cac, Rfbt & Rfbb values are okay or need any fine tuning?

thanks and regards

Adarsha A N

over 3 years ago

0 David_Daniels over 3 years ago

TI__Mastermind 20830 points

Use the derated Cout for Vinj_out.

I calculate 10.2kohm for the Vout of 4.99V and 10k for 5.08V.

Equation 14 in datasheet has the N factor. I calculate N as 8.3 using values in the webench schematic and the >4 is the stability criteria for the vout > 3.3V

0 ADARSHA A N over 3 years ago in reply to David_Daniels

Prodigy 245 points

hi David Daniels,

thanks for the reply,

1) I hope " 10.2kohm for the Vout of 4.99V and 10k for 5.08V." is regarding Rfbb resistor?

2) and also is there any limit consideration for VINJ_OUT to ensure the selected Rr, cr, Cac, values are correct?

thanks and regards

Adarsha A N

0 David_Daniels over 3 years ago in reply to ADARSHA A N

TI__Mastermind 20830 points

Yes, the 10k is Rfbb.

Select the Cout based on your load's transient and ripple requirements then

choose the Rr, Cr, and Cac.

A typical design or load will specify the Vout ripple as a percent and can be 0.5% to 1.5%.

Sometimes the ripple requirement for a load is very low and less than 0.5%.

Eq 14 in section 8.2.2.3 has Cout as a variable and gives the N factor for stability criteria.

The datasheet recommends keeping Vinj_sw < 50mV.

0 ADARSHA A N over 3 years ago in reply to David_Daniels

Prodigy 245 points

hi,

Can i get layout guidelines for ripple injection circuit..

thanks and regards

Adarsha A N

0 David_Daniels over 3 years ago in reply to ADARSHA A N

TI__Mastermind 20830 points

Figure 38 on page 26 in the following www.ti.com/.../tps53315.pdf

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WEBENCH® Tools/TPS53315: ripple injection circuit