LMR51450: quick soft-start function

Lillian Liu(SH)

Part Number: LMR51450
Other Parts Discussed in Thread: TPS62903, LMR14050,

Tool/software:

Hi team,

Could you please check if you have recommended DCDC converter that support 36V input voltage and a fixed soft-start time less or equal than 0.5ms? i.e. TPS62903@17V

Or DCDC converter that support 36V input voltage with adjustable soft-start function to achieve 0.5ms ss time?

Thanks

Lillian

3 months ago

0 Frank De Stasi 3 months ago

TI__Guru 65535 points

Hello

We do not have a converter that features a 0.5ms soft-start.

Our converters that have adjustable soft-start can only by adjusted for longer than the built-in time.

Thanks

0 Lillian Liu(SH) 3 months ago in reply to Frank De Stasi

TI__Expert 3880 points

Hi Frank，

if LMR14050 could adjust soft start time to 0.5ms?

if built-in time is the Minimum controllable on time?

And if it work, is any more cost effective recommendation?

Thanks

Lillian

0 Frank De Stasi 3 months ago in reply to Lillian Liu(SH)

TI__Guru 65535 points

Hello

The Ton-min is not related to the soft-start. That

specification corresponds to the minimum time that the HS FET can stay on.

Thanks

0 Lillian Liu(SH) 3 months ago in reply to Frank De Stasi

TI__Expert 3880 points

Hi Frank,

You mean that the built-in time is HS FET can stay on time? Which data I could find it in datasheet?

And so you mean that LMR14050 could not adjust soft start time to 0.5ms, right?

Could you check which device in your product line could support the fastest soft start？

Thanks

Lillian

0 Frank De Stasi 3 months ago in reply to Lillian Liu(SH)

TI__Guru 65535 points

Hello

The Ton-min that you see in the data sheet is related to the HS FET duty cycle time, and is not related to the

soft-start time.

The data sheet for the LMR51450 does not show a soft-start time; it is only mentioned as typical in the text of the data sheet.

For other data sheets, you may be able to find it in the EC table under "soft-start" time.

Thanks

0 Lillian Liu(SH) 3 months ago in reply to Frank De Stasi

TI__Expert 3880 points

Hi Frank,

Thanks for your reply, but I still confused if LMR14050 could adjust soft start time to 0.5ms? And which device in your product line could support the fastest soft start?

Thanks

Lillian

0 Frank De Stasi 3 months ago in reply to Lillian Liu(SH)

TI__Guru 65535 points

Hello

Let me assign your post to the engineer that is working on E2E for October.

Thanks

0 Rahil Ajani 3 months ago in reply to Lillian Liu(SH)

TI__Expert 6560 points

Hi Lilian,

0.5ms soft start is pretty fast for a simple switcher. LMR51450 is a newer device with better efficiency and EMI, we recommend that as a replacement for LMR14050. It has a 5ms internal soft start.

Regards,

Rahil

0 Lillian Liu(SH) 3 months ago in reply to Rahil Ajani

TI__Expert 3880 points

Hi Rahil,

Could you check the fastest soft start time of LMR14050?

Thanks

Lillian

0 Lillian Liu(SH) 3 months ago in reply to Lillian Liu(SH)

TI__Expert 3880 points

Hi Rahil,

Could you help check this case for me?

Thanks

Lillian

0 Rahil Ajani 3 months ago in reply to Lillian Liu(SH)

TI__Expert 6560 points

Hi Lillian,

the fastest soft start time possible is 3.2ms

Regards,

Rahil

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LMR51450: quick soft-start function