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TI_RS232_MAX3222IPWR Questions

Philip
Expert 1510 points

I am using MAX3222IPWR for my customer TV project. It will operate in 9600bps in general.

I have some questions on the application side.

 My question is:

Q1: For unused input pin (13-DIN1, 16-RIN1), should I leave it OPEN or short to GND/Vcc? 

Q2: If unused pin is open, any side effect/issues?

Q3: If it needs to be short to GND/Vcc, do you have any application note I can refer to (I cannot get any application note for this part for the site)?

Looking for your reply soonest as possible.

Thanks and Best Regards,

Philip

  • 0
    TI__Guru**** 165316 points

    Q1: For unused input pin (13-DIN1, 16-RIN1), should I leave it OPEN or short to GND/Vcc? 

    DIN1 should be connected to VCC or GND because digital inputs must be pulled high or low. RIN1 has internal 5k resistor and the pin can be left open. Zero volts is a valid low input.

    Q2: If unused pin is open, any side effect/issues?

    If a digital input is left floating, it is unknown whether it will be interpreted as low or high also ICC may increase.

    Q3: If it needs to be short to GND/Vcc, do you have any application note I can refer to (I cannot get any application note for this part for the site)?

    I do not know a specific app note for this device. The data sheet tables give a lot of direct and inferable information.

     

    Regards,
    Ron M.     

  • 0 in reply to Ron Michallick
    Expert 1510 points

    Hi Ron,

    Thanks a lot for your quick feedback.

    Just question to Q2 answer.

    As my customer has the end product running in the production, they would like to know what would happen if pin 13-DIN1 is just left open/floating without any connection to Vcc or GND? What would happen to the IC performance if ICC/supply current increase? Any reliability issue? or noise performace issue? or anything?

    Thanks and Best Regards,

    Philip 

  • 0 in reply to Philip
    TI__Guru**** 165316 points

    There can be problems with the floating input. See the document below.

    Implications of Slow or Floating CMOS Inputs (Rev. C)
    http://focus.ti.com/general/docs/litabsmultiplefilelist.tsp?literatureNumber=scba004c