TPS22919: Soft start (rise time) when ON pin turn on before VIN

Yusuke Mukuno

Expert 7395 points

Part Number: TPS22919
Other Parts Discussed in Thread: TPS22975, TPS22976

HI Expert,

My customer has a question about TPS22919 rise time.

Normal case, supplied VIN before VON turn on.

TPS22919 should work on datasheet description in this case.

When VON turn on before VIN, How does TPS22919 work for start up?

Vin UVLO > T_delay > T_rise (?)

Rising time is not applied, and the switch fully on from Vin UVLO (?)

other (?)

Thanks

Muk

over 3 years ago

0 Andy Robles over 3 years ago

TI__Genius 13470 points

Hi Muk,

Welcome to E2E!

The case condition when VON turns on before VIN is not tested. Under these conditions the device will not get damaged, but the assumption is that there is no timing requirements on the application. We can not guarantee any timing characteristics when the device is used under these conditions.

Best regards,

Andy Robles

0 Yusuke Mukuno over 3 years ago in reply to Andy Robles

TI__Expert 7395 points

Hi Andy-san,

Thank you for your answer.

Customer have some additional questions.

For example, in case of ON pin pulled up to Vin by resistor, ON pin is raised same timing with Vin. How will TPS22919 work?

Does TPS22919 have UVLO for Vin?

Also, Customer is considering TPS22975 and TPS22976.

Do you have power sequence requirement between Vbias, Vin and ON? (Must requirement)

Thanks

Muk

0 Andy Robles over 3 years ago in reply to Yusuke Mukuno

TI__Genius 13470 points

Hi Muk,

To ensure timing characteristics in the datasheet when tying ON-pin to VIN, the customer must add a capacitor from ON-pin to ground to create an RC delay on the ON-pin to keep both signals from having the same timing. If the RC delay is not included the device will still be functional, but the timing of the load switch might not be as described in the datasheet.

The UVLO of the TPS22919 is 1.6V as stated in the min input voltage range spec in the recommended operating conditions section of the datasheet.

For devices with VBIAS, a voltage must be applied to VIN and VBIAS before VON get toggled high to ensure timing described in the datasheet.

Best regards,

Andy Robles

0 Yusuke Mukuno over 3 years ago in reply to Andy Robles

TI__Expert 7395 points

Hi Andy-san,

Thank you for your answer.

I have one more question.

For devices with VBIAS, do you have any sequence requirement between Vbias and Vin?

Vbias > Vin : I think, it is normal case.

Vin > Vbias : is it ok?

Thanks

Muk

0 Andy Robles over 3 years ago in reply to Yusuke Mukuno

TI__Genius 13470 points

Hi Muk,

For VBIAS and VIN there is no required sequence as the switch will be disabled until ON-pin gets toggled high. As long as both VIN and VBIAS get applied before ON-pin gets toggled high the sequence won't matter.

Best regards,

Andy Robles

0 Yusuke Mukuno over 3 years ago in reply to Andy Robles

TI__Expert 7395 points

Hi Andy-san,

Thank you very much for your answer!!

Thanks

Muk

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TPS22919: Soft start (rise time) when ON pin turn on before VIN