TPS7A24: How to calculate the dynamic thermal in short time?

JIAN JIN

Part Number: TPS7A24

Dear Team,

I'm using TPS7A2401DBVR currently.

This device is going to trigger two relays together in worst case in our design.

- The max. load is 215mA at 33ms pulse length in worst case. Then the waiting time for next pulse is very long, it's designed 5.5s min.

- We have the concern about the max. junction temp. and whether the LDO output could be switched off.

Is it possible to calculate the dynamic max. junction temp.? But we don't have its dynamic thermal resistance @33ms, and its RDS_ON (Drain-Source On-State Resistance for the MOSFET inside).

So, it would be very appreciate to give us a hint how to do this kind of calculation or support some more data?

Thanks a lot in advance!

over 2 years ago

0 Stephen Ziel over 2 years ago

TI__Mastermind 37185 points

Hi Jian,

I am reviewing your question and will get back to you within 2 business days.

Thanks,

Stephen

0 Stephen Ziel over 2 years ago in reply to Stephen Ziel

TI__Mastermind 37185 points

Hi Jian,

I have submitted a thermal request for a transient thermal resistance per your specifications. It can take up to 2 weeks to work through the queue and get a response. I'll reply back when I have more information. Thanks for your patience.

Thanks,

Stephen

0 JIAN JIN over 2 years ago in reply to Stephen Ziel

Prodigy 205 points

Thanks a lot for your effort! Waiting for your information!

Have a nice day!

0 Stephen Ziel over 2 years ago in reply to JIAN JIN

TI__Mastermind 37185 points

Hi Jian,

Okay thanks, I'll let you know when I have additional feedback to report.

Thanks,

Stephen

0 Stephen Ziel over 2 years ago in reply to Stephen Ziel

TI__Mastermind 37185 points

Hi Jian,

What is the power dissipation during the transient condition? We are ready to provide the transient thermal resistance but we need to know the pulsed watts to do so. Let me know if you still need this information.

Thanks,

Stephen

0 JIAN JIN over 2 years ago

Prodigy 205 points

Hi Stephen,

Thanks for your reply firstly. But sorry I just noticed your reply, since I mute the reminding in the e-mail unintentionally. But don't know how to un-mute it.

And yes, I'm waiting for your results all the time. :-)

The max. output voltage in our application is 4.78V, so the max. power dissipation is 4.78V*0.215A = ~1W for 33ms duration.

Thanks, have a nice weekend in advance!

0 Stephen Ziel over 2 years ago in reply to JIAN JIN

TI__Mastermind 37185 points

Hi Jian,

I've provided this information to the thermal modeler and I'm waiting to hear back on their results.

Thanks,

Stephen

0 Edgar Acosta1 over 2 years ago in reply to JIAN JIN

TI__Genius 12775 points

Hi Jian,

Here are the results for the RC network.

The result for the 215 mA for 33 ms case is preloaded into the results, but the inputs can also be changed for any power profile needed

5DBV_19409_TPS7A2401_RC_Network.xlsx

Best,

Edgar Acosta

0 JIAN JIN over 2 years ago

Prodigy 205 points

Hi Edgar and Stephen,

You're so professional! I will discuss this topic with my German colleague. Thanks a lot!!

Have a nice day!

JIN JIAN

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TPS7A24: How to calculate the dynamic thermal in short time?