enter image description hereI want to use TTL-RS485 Circuit as in the attachment. The circuit is working when I use ADM483 Transceiver for U1. It can provide communication. However the circuit is not working when I use MAX3430 for U1. I observe enable and tx signal is fine and same as in ADM483. but there is no communication. when I remove R3, it try to communicate but it cannot receive because receive enable is disabled. I mean it transmit but not receive. why does not the circuit work with MAX3430? why does it work with ADM483?


1 Answer 1


It is likely that the problem is the VCC1 voltage that you are using. If that voltage is +5V then I would expect the ADM483 to work just fine. It is designed to be used with a 5V supply.

On the other hand the MAX3430 is designed to be used with a 3.3V power supply. In fact the part's absolute maximum VCC is 5V but that is on the edge of being damaged.

You did not link data sheets in your question, which is highly recommended here, so I wonder if you have carefully read the data sheets for these two parts. Doing so would have revealed what I have pointed out above. There may be some other differences between the parts which could only be determined by careful data sheet examination.

  • \$\begingroup\$ Thanks for your reply. Sorry that I forgot to specify VCC1 value. VCC1 is 3.3V. \$\endgroup\$
    – mehmet
    Commented Jun 26, 2018 at 13:48
  • \$\begingroup\$ @mehmet - The ADM483 needs to be operated at a VCC of 5.0V +/-5%. Operation outside that range is not specified and you should not try to operate it at 3.3V. \$\endgroup\$ Commented Jun 28, 2018 at 1:30

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