Question about RS-485 Tranceiver

Hi Kazu,

Mixing transceivers with Vcc = 3.3V and Vcc = 5.0V is acceptable on the same common bus, provided that you terminate the bus with two termination resistors. The termination resistor value should equal the characteristic impedance of the bus cable.

Condition 2 is acceptable: Vcc = 5V and logic voltage = 3.3V.

The ADM3065E (just released) does not have a logic voltage (Vio) pin. However, we will be releasing a model with a Vio pin in the next month (by the end of May '17).

I am checking if condition 1 is acceptable. Is this a likely condition for your application? I would think that 'Condition 2' is a much more likely condition.

Best regards,

Richard

tnelson654 san,

Thank you for supporting this case. The number of transceivers is maximum 64 pcs on the bus.

ADM3085E is a little expensive to me, so I have a question about ADM3065E to you.

Using ADM3065E under the following conditions are acceptable?

1): Vcc=3.3V, Logic voltage=5V,   2): Vcc=5V, Logic voltage=3.3V

**Logic voltage is not decided yet but it will be 3.3V or 5V.

**Data rate needs 10M~20Mbps

Regards,

Kazu

Hi Kazu,

For the new 'ADM3065E' models that will have Vio pin, condition 1 where Vio > Vcc will not cause damage or reliability issues for the part.

Best regards,

Richard

Kazu san, we need to clarify your requirements.

Do you mean "at least 64 transceivers" on the bus? (A part that allows 128 or 256 transceivers will work properly with 64 transceivers on the bus.)

By "5V and 3.3V" do you mean either one or the other, as compared to anything in between? Or do you mean 3.3V logic levels with a 5V analog supply? Based on your attachment, it is perfectly acceptable to mix 3.3V transceivers and 5V transceivers on the same bus as long as they are RS-485-compliant on that supply voltage. This is true for the Analog Devices' transceivers as well as Linear Technology's (which are now part of ADI).

What data rate do you require?

Have you considered these:

ADM3095E with a separate logic supply, ADM3065E with standard pinout, LTC2862-65 similar, but with slightly higher voltage fault protection

One of these parts should meet your requirements.

Hi Richard,

Thank you for supporting this case.

For logic voltage=3.3V case, I can use ADM3065E. For logic voltage=5V case, I can use the new ADM3065E.

I have another question. Some products have the following feature.

"Interoperable with 5V logic"  Does it mean that it accepts Vcc=3.3V and logic voltage=5V?

Best Regards,

Kazu

Hi Kazu,

Yes, this can be interpreted as accepting larger logic voltages than Vcc on inputs.

Best regards,

Richard

Hi Richard,

When will the new ADM3065E be released?

Bet Regards,

Kazu

Hi Kazu,

The ADM3065E is released, please see these webpages:

http://www.analog.com/en/products/interface-isolation/rs-232-rs-422-rs-485/interface-rs-485-rs-422/adm3065e.html

http://www.analog.com/media/en/technical-documentation/data-sheets/ADM3065E.pdf

http://www.analog.com/media/en/technical-documentation/application-notes/AN-1397.pdf

http://www.analog.com/media/en/technical-documentation/user-guides/EVAL-ADM3065EEBZ-3065EEB1Z-UG-1000.pdf

Best regards,

Richard

Yes, that's correct.

Best regards,

Richard

Hi Richard,

Sorry, I'd like to know about the models that will have Vio pin accepts Vio > Vcc condition.

From your mail, it seems I can have samples in the end of May '17.  Am I correct?

Best Regards,

Kazu