LM74700-Q1: Selecting TVS in 60V input application

Fraser Lawson1

Part Number: LM74700-Q1
Other Parts Discussed in Thread: LM5050-1, LM5050-2

Hello.

I would like to use the LM74700-Q1 as a reverse polarity protection device in an application where the input DC voltage can be up to 60V.

However, my problem is finding a suitable TVS to protect the device (max i/p voltage of LM74700-Q1 = +/-65V). Obviously, we need the TVS breakdown voltage Vbr to be >= 60V but then this gives a clamping voltage of approx. 98V.

This clamping voltage is beyond the 65V absolute maximum rating for the LM74700-Q1.

My question is - Can the LM74700-Q1 survive "transients" up to 98V of defined duration e.g IEC610004-5 8/20us?

over 5 years ago

0 Karikalan Selvaraj over 5 years ago

TI__Genius 16305 points

Hello Fraser,

For 60V DC operation and surge test requirements as per IEC61004-6 8/20us, we recommend to use LM5050-1 or LM5050-2 due to 100V absolute maximum ratings.

LM74700-Q1 may not be suitable here due its 75V absolute maximum ratings.

Regards,
Kari.

0 Fraser Lawson1 over 5 years ago in reply to Karikalan Selvaraj

Prodigy 240 points

Thanks for your prompt reply, Kari.

So if we use the LM5050-1 for Reverse Polarity protection - we need some extra components e.g diode D3 in Figure 31 of data sheet?

Otherwise it will only work as an OR-ing controller - am I correct?

Regards,

Fraser

0 Karikalan Selvaraj over 5 years ago in reply to Fraser Lawson1

TI__Genius 16305 points

Hi Fraser,

I would need more time to look into your follow up question and will get back by before end of the week.

Hope this timing is fine, if not let me know.

Regards,

Kari.

0 Karikalan Selvaraj over 5 years ago in reply to Karikalan Selvaraj

TI__Genius 16305 points

Hello Fraser,

Yes D3 is required for reverse input polarity protection.

But to function as ORing (without reverse input polarity protection), D3 is not required.

Regards,
Kari.

0 Fraser Lawson1 over 5 years ago in reply to Karikalan Selvaraj

Prodigy 240 points

Thank you, Kari.

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LM74700-Q1: Selecting TVS in 60V input application