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MAX3232E: IC is all unavailable if ROUT2 is connected to GND.

Chase Jeong
Genius 5440 points
Part Number: MAX3232E

Tool/software:

Dear TI experts,

my customer tests MAX3232EIPWR in their own PCB.

And if they connect ROUT2 to GND, all IC is unavailable.

I think that only channel 2 (DIN2-DOUT2, RIN2-ROUT2) is uavailble is right operation, but even channel 1 is also unavailable if ROUT2 is connected to GND.

Could you find the reason? I attach the schematic for yout convenience.

(If they apply GND to ROUT2 using SW8, RIN1-ROUT1 line is unavailable too.)

Best regards,

Chase

  • 0
    Guru 275410 points

    ROUT2 is a push/pull output that, when the bus is idle, drives high. Shorting it to ground exceeds the absolute maximum ratings and shorts the power supply, so it is plausible that the rest of the chip no longer works.

    Unused outputs and bus inputs should be left open. Unused logic inputs (DIN1) must no be left floating.

  • 0
    TI__Guru 57730 points

    Hi Chase,

    Clemens is correct.

    The Rout pin is likely causing the device to short if it's connected directly to GND. When this occurs, you are also likely causing the switching regulator to deregulate since it cannot source the current which would likely affect the other RS232 side outputs (ROUT1). The worst case scenario is the device heats up past its absolute max value and breaks.

    Input pins like DIN1 should not float. (not likely causing the issue you're seeing though).

    -Bobby