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Help with MAX3232

Ian Craig
Prodigy 10 points

Other Parts Discussed in Thread: MAX3232

Hi

 

I have a problem with a board with a MAX3232 device. What happens is if the MAX3232 is powered with a device (in this case a standard PC serialport) connected to the RX Input the charge pump doesn't appear to work. If you remove the connection and reconnect everything is fine and if you power the MAX3232 before connecting the PC everything is ok. It is only if there is -12V on the RX input when the MAX3232 is powered up that this happens. I have used these devices in plenty other designs over the years with no issues. On the board the MAX3232 is connected to a NXP LPC1752 Cortex-M3 processor.

 

Has anybody any idea of what could cause this behaviour?

 

Thanks

Ian

  • 0
    TI__Guru**** 171346 points

    Hello Ian,

    This effect has not been reported before. Can you measure the voltages on the device pins when this anomaly occurs? Use an oscilloscope to see if there is any clocking. The pin voltages will be helpful in determining the root cause.

    Does this happen on more than one MAX3232 device? Is it a new design?

    Regards,
    Ron Michallick