SN65HVD72: SN65HVD72

Charles Corris

Part Number: SN65HVD72

Due to the recent shortage of semiconductors, we purchased a quantity of sn65hvd72 parts offshore, and when used in conjunction of earlier production parts, we see an offset of the data (see pictures).

Although the data decodes correctly we are concerned about this phenomenon possibly causing an issue when used in large volume. I do not see anything in the datasheet about data offset specification.

James Corris CDI Electronics

Waveform with early production

Waveform with latest devices

over 3 years ago

0 Clemens Ladisch over 3 years ago

Guru 317260 points

Apparently, there are two transmitters, with different drive strengths.

The drive strength is implied by the RS-485 specification, so this should not happen. I would guess that you have a counterfeit device that was designed for a 5 V supply.

0 Charles Corris over 3 years ago in reply to Clemens Ladisch

Prodigy 20 points

Clemens,

Are you a TI representative?

0 Tyler Townsend over 3 years ago

TI__Mastermind 47998 points

Hi James,

It looks like these two waveforms show two different devices / drivers. The SN65HVD7x RS-485 transceivers do not have a built in offset as shown in the second scope capture. Like Clemens stated, it could be possible these are counterfeit devices labelled as TI parts. Although these devices will work and decode data correctly, you do reduce your VOD which creates a smaller noise margin, thus a less robust RS-485 communication system.

Please let me know if you have any more questions.

Regards,

Tyler

0 Charles Corris over 3 years ago in reply to Tyler Townsend

Prodigy 20 points

Tyler,

They are two different devices, one with a chip from an earlier production lot, and one (with the higher signal amplitude) from the lot in question.

0 Tyler Townsend over 3 years ago in reply to Charles Corris

TI__Mastermind 47998 points

Hi James,

I see that these two devices are the same part number, but different chips from different production lots. Does your question of concern rest with a quality issue, or are you asking if the device will still work given this output voltage difference?

Can you confirm that the devices were bought from an approved TI source?

Regards,

Tyler

0 Eric Hackett over 3 years ago in reply to Charles Corris

TI__Guru 74282 points

Charles,

Can you share the topside markings of the ICs you have? Clemens may be right here, and I can check with one of our internal systems if the lot trace code of the ICs exists in our system.

Regards,

Eric Hackett

0 Charles Corris over 3 years ago in reply to Eric Hackett

Prodigy 20 points

Eric,

Did you get the photos of ICs?

If not, here they are again.

0 Eric Hackett over 3 years ago in reply to Charles Corris

TI__Guru 74282 points

Charles,

I did not, where were they sent? And the link in your last message doesn't go anywhere for me.

Regards,

Eric Hackett

Interface

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SN65HVD72: SN65HVD72