SN65LBC184: Genuine RS485 Transceivers?

Greg Reynolds

Part Number: SN65LBC184

Hi,

I am trying to debug an issue for my customer involving the above RS485 transceiver. I'd like to know some expert thoughts on why these voltage levels might be different.

In the scope trace below, the first burst is the modbus master communicating with the device, the second burst is the device replying.

The yellow trace shows the response when the chip fitted is marked "65LBC184". I note that the datasheet only seems to list this as being a marking on the PDIP package, but this is an SOIC.

The red trace shows the reponse when the chip fitted is marked "6LB184".

Please see pictures of the markings attached. Are we dealing with a genuine chip here? I know the one marked 6LB184 is genuine because I purchased directly from TI, but the other one is currently suspect and came from the subcontract manufacturer.

3 months ago

0 Greg Reynolds 3 months ago

Prodigy 50 points

Sorry, I forget to say that the traces show the "A" line of the RS485.

0 BOBBY 3 months ago in reply to Greg Reynolds

TI__Guru* 78301 points

Greg,

From what I can see, there is no lot trace code on that last image (generally the SOIC packages will have it on the top as the 3rd line).

I also went through our internal database to look at top markings for our SOIC packages and all of them have some sort of TI logo. I've never seen a device have a 'UMW' marking.

I don't think the device marked UMW is a TI device.

-Bobby

0 Greg Reynolds 3 months ago in reply to BOBBY

Prodigy 50 points

Hi Bobby,

Thanks for your reply.

It turns out "UMW" are a company that are making a clone of this chip, my customer found it on DigiKey:

https://www.digikey.gr/en/products/detail/umw/SN65LBC184DR/16705889

Clearly though, it is not an exact clone because the output waveforms are observably different.

Best wishes,

Greg

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SN65LBC184: Genuine RS485 Transceivers?