TPSM83100: Soft-start ramp time

Shunsuke Yamamoto

Part Number: TPSM83100

Tool/software:

Hi team,

My customer has been evaluating TPSM83100 by TPSM83100EVM, and found out soft-start ramp time is not in the typical value in some cases.

1. When the output load is 0 ohm which means no load, Td(RAMP)=0.16ms.

2. When the output load is electric load and output current is 0.49A, Td(RAMP)=7.15ms.

3. When the output load is 10 ohm, Td(RAMP)=0.4ms.

I also found that IL(lim_SS) decides soft-start ramp time is fast or not. May I know the value of IL(lim_SS)? My customer cannot define the soft-start ramp time in customer's use case based on the datasheet.

Best regards,

Shunsuke Yamamoto

over 1 year ago

0 Tao Zhang over 1 year ago

TI__Mastermind 32350 points

Hi Shunsuke-san,

This current limit is 500mA typically. it is a peak current value.

Yes, you understanding is correct, when load is low in start-up phase. Actual Tss will be decided by Ilim_ss， but not internal ramp time.

Regards

Tao

0 Shunsuke Yamamoto over 1 year ago in reply to Tao Zhang

TI__Expert 7671 points

Hi Tao,

Thank you for the reply. How about the relationship between IL(lim_SS) and td(EN) and td(ramp)?

How do we determine the exact SS time based on the output current?

Best regards,

Shunsuke Yamamoto

0 Tao Zhang over 1 year ago in reply to Shunsuke Yamamoto

TI__Mastermind 32350 points

Hi Shunsuke-san,

There is no relationship beteween IL(lim) and Td internal, they are just two logic blocks.

I think there is no good way to calculate the exact SS time once current limit is take over during start-up. Simulation or bench test should be a good choice.

Regards

Tao

0 Shunsuke Yamamoto over 1 year ago in reply to Tao Zhang

TI__Expert 7671 points

Hi Tao,

Do you mean customers should estimate soft start time based on the output current in all situations? I think it wastes of time for customers. Could you please also double check if it is really no good ways to estimate soft start time?

Best regards,

Shunsuke Yamamoto

+1 Tao Zhang over 1 year ago in reply to Shunsuke Yamamoto

TI__Mastermind 32350 points

Hi Shunsuke-san,

Since customer has some test data already, i think they can just use 7.55ms as soft-start time when load is higher than 0.49A.

But when Iout is lower, i do not down how to evalute except simulation or bench test.

Regards

Tao

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TPSM83100: Soft-start ramp time