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Questions about using MAX3485 and MAX3088 together

Category: Hardware
Product Number: MAX3485, MAX3088
Software Version: .

Our company is using it for RS-485 communication.
1) MAX3088 uses existing mass-produced products
2) Scheduled to be changed to MAX3485 for new mass production

For the reasons above, please answer the following three questions.

1. Mixed use of MAX3088 and MAX3485.
 - Existing products use MAX3088 for RS-485 communication.
 - Additional production products use the MAX3485 for RS-485 communication.
 - When using mixed products, check if there are any abnormalities.

2. Whether to remove the terminating resistor.
 - The length of the line using RS-485 Max. Within 100M.
 - Connected products max. Within 7 devices.
 - Termination resistance 110Ω is connected to each product.
 - As a result of the current test, if a product is added to the RS-485 line, the RS-485 communication voltage level is low.

3. Combination of RS-485 A/B line protection circuit.
 - Existing products have 485 A-line pull-down and 485 B-line pull-up applied.
 - 485 -> 4 of 1N4148WS (switch diode) is applied to 485 A/B Line 1st Fix due to poor communication. (VCC/GND line)
 - 2 SM712-02HTG(TVS) 485 A/B Line applied -> 2nd correction due to poor communication of 485 ground line)
 - When using mixed using protect diode, check if there are any abnormalities.

Please reply to confirm whether it is applicable to mass production.

Thank you

  • The two products operate at different supply voltage: MAX3088 at VCC = 5V while MAX3485 at VCC=3.0V. The system performance will be different with mixing 5V bus with 3V bus compared to all 5V in entire RS-485 network. Can you discuss with ADI local FAE about the detail system architecture so that we can better support  you, or send an email to me at  Thanks

    Best Regards,