LMZ31710: Regarding capacitor (C_SS/TR) value for soft start delay of 32 ms

Sahil Singh

Part Number: LMZ31710

Tool/software:

Hello,

I am using LMZ31710 IC for 12V to 3.3V in my design. As per the design requirements, 32 ms soft start delay (T_SS = 32ms) is required. In the datasheet, soft start capactior values for soft start delay upto 9.8 ms is only given. Further, no equation is given in datasheet for C_SS value calculation. Please suggest the soft start capacitor value for T_SS = 32ms with relevant references.

Thanks and Regards,

Sahil

over 1 year ago

0 Calan Elaya over 1 year ago

TI__Genius 11145 points

Hello Sahil,

A response will be posted this week.

Thanks,
Calan

0 Savith Kumar Rayakanti over 1 year ago in reply to Calan Elaya

TI__Expert 5740 points

Hi Sahil

pls see the below e2e post on soft start,

you can calculate the soft start cap as explained in this post

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1325921/lmz31710-about-the-slow-start-design-of-lmz31710/5101934?tisearch=e2e-sitesearch&keymatch=Savith#5101934

Thank you

Savith

0 Sahil Singh over 1 year ago in reply to Savith Kumar Rayakanti

Prodigy 155 points

Thanks Savith for your reply.

Can you please tell is there any provision to ENABLE LMZ31710 instead of using slow start capacitor as there is no EN pin in this IC. As per my design, I want to give an ENABLE signal to LMZ31710 through FPGA. Please repond to the same.

Thanks and regards,

Sahil

0 Calan Elaya over 1 year ago in reply to Sahil Singh

TI__Genius 11145 points

Hi Sahil,

A response will be posted this week.

Thanks,
Calan

0 Savith Kumar Rayakanti over 1 year ago in reply to Sahil Singh

TI__Expert 5740 points

Hi Sahil

Pls see section 7.3.18 of the datasheet, which explain the power sequencing through ext singnal on INH/UVLO pin

-Savith

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LMZ31710: Regarding capacitor (C_SS/TR) value for soft start delay of 32 ms