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TPS61088: Not Working As per Web-Bench Design

kamlesh patel
Prodigy 120 points
Part Number: TPS61088

we have generated Boost Converter Using web-bench Design.
which has parameters are as per below.
Vin:- 3.2v Min to 3.7V max
Vout:- 5.3V @5A.
please go through below attached schematic and layout.

we have made some changes as per our calculation which is as per below.
We change the Comp pin(Pin-18 of IC) component as per below.
Designator schematic value updated value
C67 - 27pf-25v 150pf-25v,
C68 - 560pf-25v 1nf-25v,Qty=2,
R55 - 36.5k-25v 20k-25v
L4 - 680nH,12.75A 2.2uH,10A(ASPI-0630LR-2R2M-T15)
All component packages are 0603 packages.

Test case:-
Vin:- 3.7V@5.5A Single Cell
Vout:- 5.3V@ No load
Vout:- 3.7V@3.5 Ohm Resistive Load

so it is not working as per web bench design.

So please suggest the solution for it.

thanks to all in advance.

  • 0
    TI__Expert 4760 points

    Hi Kamlesh,

    It seems the device is current limited.

    1)Check the voltage on C63 to verify if it is much lower than 3.7V;

    2)Check if R54 is 105k, if wrong resistance is on the board the device could be current limited;

    3)Recommend R55 as 4.5k, C68 as 5.6nF;

    4)The C60 should be placed next to IC, but this should not cause the behavior. 

  • 0 in reply to Yichen Xu
    Prodigy 120 points

    Dear Vichen Xu

    thanks for reply

    I have changed R55 and C68 values as per your suggestion and they work properly.

    but can you give a brief calculation for it so I can better understand the mistake

    you can share me on my email id:- kamlesh.patel@promptsoftech.in or share your email id so we can discuss.

  • 0 in reply to kamlesh patel
    TI__Expert 4760 points

    Hi Kamlesh,

    I’m glad that your problem is solved.

    I calculated the parameters according to equation 16,18,19,20 in datasheet. There are two points to note. 1) I set crossover frequency less than 1/5 RHPZ, 5kHz; 2) I use effective capacitance to calculate R55, I assume it is 47uF, half of your nominal capacitance in your case.