SN65HVD76: Suggestion on selecting suitable part for RS485 transceiver

Sachin Kurawatti

Part Number: SN65HVD76
Other Parts Discussed in Thread: SN65HVD73

Hi,

I need to select RS485 transceiver. Below are generic spec required.

Full Duplex
Data rate: upto 5Mbitsps
VCC: 3.3V
Driver/Transmitter Differential VOUT (with load): min 1.5V
common mode range (CMR): Min -7V to +12V
Differential signalling with a very sensitive (±200mV) Rx
A receiver input resistance of approximately 12kΩ
fail safe function
High ESD transceiver

For above features there are a lot of selection devices available. Please can anyone suggest best way to select part number in that lot of devices.

Regards,

SMK

over 6 years ago

0 Lucas Schulte9 over 6 years ago

TI__Expert 6955 points

SMK,

The difference in the devices that meet your specifications will mainly be maximum data rate, maximum ESD voltages in KV, and the presence or lack of Enables. For example, If only 12KV of ESD protection is needed and you also need the Enables then the SN65HVD73 would suffice. How high ESD protection do you need?

-Lucas

0 Sachin Kurawatti over 6 years ago in reply to Lucas Schulte9

Prodigy 130 points

Hi Lacus,

Got you point.
One more input I may request you.
Where can I find Fault Protection (V) voltage details in Datasheet?

Regards,
SMK

0 Lucas Schulte9 over 6 years ago in reply to Sachin Kurawatti

TI__Expert 6955 points

SMK,

The Fault Protection voltages can be found under the Absolute Maximum Ratings section. The Fault Protection voltages is the maximum voltages at the bus pins.

-Lucas

0 Sachin Kurawatti over 6 years ago in reply to Lucas Schulte9

Prodigy 130 points

Thnk you

0 Sachin Kurawatti over 6 years ago in reply to Sachin Kurawatti

Prodigy 130 points

Dear Lucas,

Normally RS485 is differential signal.
When do you suggest need to have opto isolation for RS485 interface in an industrial environment?
What may be regular specification for external ESD diode or other protection ckt that may be required with RS485 transceivers?

Please suggest.

Regards,
SMK

0 Max Robertson over 6 years ago in reply to Sachin Kurawatti

TI__Guru 62910 points

Hello SMK,

Lucas is out of the office today, so I will try to help out instead.

Isolation is typically introduced when there is a concern for safety (e.g., in order to ensure that there are no potential conductive paths between a human interface and a higher-voltage domain) or when needed to ensure reliable communication between systems with potentially large difference in their ground reference voltages. (RS-485 transceivers are generally able to communicate among nodes that do not share a common reference voltage as long a the difference in potential between system grounds is within a few volts. Beyond that, though, it is good to try to share a common ground, and introducing isolation is a good way to make sure that this additional ground wire does not result in ground loops.)

You can read more about RS-485 grounding and the benefits of isolation in Section 11 of this application note:

www.ti.com/.../slla272c.pdf

To understand more about how to review ESD diode specification to make sure they are suitable for a given interface transceiver, please take a look at this blog:

e2e.ti.com/.../how-to-choose-a-tvs-diode-for-rs-232-rs-485-and-can-based-on-voltage-ratings

Please just let us know if you have further questions.

Best regards,
Max

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SN65HVD76: Suggestion on selecting suitable part for RS485 transceiver