LM74800EVM-CS: Design of Unsuppressed Load Dump Protection using IC LM74801QDRRRQ1

Tanveer Ahmed

Part Number: LM74800EVM-CS
Other Parts Discussed in Thread: LM74930-Q1

Tool/software:

Hi Team,

I am using TI IC with MPN# LM74801QDRRRQ1 for Unsuppressed Load Dump protection application.

It is frequently observed the Vicor EMI-EMC Filter module (MPN# MFM1714B50M50C5M08) present at the output of this circuit (VCLAMP) is going bad.

I have two queries:

Query 1:

I am suspecting that there might be some design issue from my side.

Can you please verify my Schematics.

Query 2:

Also, as per the datasheet, the TI IC with MPN# LM74801QDRRRQ1 is capable of suppressing 200V @350ms.
Is it possible for me to reduce this time to 40ms (Since the VICOR EMI-EMC filter module has 50ms of Transient time)?

Please go through the attached schematics. If this schematic is not clear, then please let me know, I will share the PDF of the Schematics.

Regards,

Tanveer Ahmed

10 months ago

0 Shiven Dhir 10 months ago

TI__Mastermind 48385 points

Hi Tanveer,

Welcome to E2E. How is the VICOR being damaged? Is it because of some EOS? Is the controller not able to clamp the surge voltage?

The schematic looks fine to me.

Regards,

Shiven Dhir

0 Tanveer Ahmed 10 months ago in reply to Shiven Dhir

Prodigy 40 points

Hi Shiven,

As per the datasheet, the VICOR module has a safe window of 50ms for a 100V transient.

And, as per the datasheet of TI IC with MPN# LM74801QDRRRQ1, it is capable of suppressing 200V @350ms.

Can we have time window of less than 50ms (instead of 350ms)?

Regards,

Tanveer Ahmed

0 Shiven Dhir 10 months ago in reply to Tanveer Ahmed

TI__Mastermind 48385 points

Hi Tanveer,

No, In that case you will have to use LM74930-Q1 which has programmable timer of clamp.

Just out of curiosity, what is the clamp level that you have set?

Regards,

Shiven Dhir

0 Tanveer Ahmed 10 months ago in reply to Shiven Dhir

Prodigy 40 points

The clamp voltage is set to 34V

0 Shiven Dhir 10 months ago in reply to Tanveer Ahmed

TI__Mastermind 48385 points

Hi Tanveer,

If the clamp voltage is set to far lower than the VICOR module ratings, how is it getting damaged?

Regards,

Shiven Dhir

0 Tanveer Ahmed 10 months ago in reply to Shiven Dhir

Prodigy 40 points

The VICOR module has maximum transient ratings of 100V@50ms.

Within how much time does the Surge Protection circuit with IC LM74801QDRRRQ1 clamps the load dump?

0 Shiven Dhir 10 months ago in reply to Tanveer Ahmed

TI__Mastermind 48385 points

Hi Tanveer,

I understand that the rating is 100V@50ms. Since the DC rating of VICOR module is +65V and the output clamp of the controller is set to 34V, how is it getting damaged?

The surge is suppressed by the operation of OV pin of the controller and has a response time of microseconds range. Sharing the behavior.

Regards,

Shiven Dhir

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LM74800EVM-CS: Design of Unsuppressed Load Dump Protection using IC LM74801QDRRRQ1