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MAX3243E: MAX3243E RX pin pull high resister

Thomas Chang15933
Expert 4770 points
Part Number: MAX3243E

Dear Team:

 Customer used Max3243E, and place pull high resister 47k ohm to 3.3V on RX (pin6).

For loopback test the Low voltage measured -4.8V , not meet spec. (-5V), if placed the pull high resister.

For some reason,  RX pin recommand not floating, so place pull high resister for getting a bias DC.

So, could we place the pull high resister? Or do we have any document about this pull high design?

  • 0
    TI__Mastermind 25705 points
    Thomas,

    RIN pin has internal 5kOhm (between 3~7kOhm) pull down to ground per RS-232 standard. I don't recommend to change it, because RS-232 driver is designed to drive this 5kOhm. Where do you see -4.8V in loopback test? Can you give a little more of detail?

    Regards,
    Hao