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Top 10 RS-485 design tips
At TI, we often get questions about whether there are any quick tips or tricks to keep in mind when designing with RS-485. So, we've put together a comprehensive list of the top commandments to remember when working with RS-485. If you have any further questions on this topic, our team is always hanging out on our E2E forum, and we would be happy to help. So, without further ado...
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How to apply them...
1) Determine maximum cable length with Chart A
2) Use twisted pair cable with Zo = 120Ω or 100Ω
3) Connect bus nodes via daisy chain
4) Terminate one cable end with RT1 = Z0
Apply failsafe biasing to the other end
Terminate this end
5) You can operate 3V and 5V devices on the same bus
6) Make stub length no longer than
7) For ± 7V GPDs use standard transceivers
For ± 20V GPDs use SN65HVD17xx
For higher GPDs use isolated transceivers
8) Terminate unused conductors with RT = Z0 to their local grounds
9) For ESD, EFT, and surge protection use SM712
10) Limit clamping current into the transceiver with 10-Ω pulse-proof or MELF resistors
Do you have your own tips? Share them with our readers below.
Learn more about TI's RS-485 transceivers, drivers, receivers and other ICs.
Learn more about TI's robust 5V-supply RS-485 transceiver with IEC ESD protection.
Check out TI's bus-polarity correcting RS-485 transceiver with IEC-ESD protection.
Have more questions? Ask them on TI's E2E Industrial Interface Forum.
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Is this graphic available with e.g. white background?
From the PDF, i can't read the light-blue texts
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