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LMH1218 - How should we treat the unused pins ?

Kawai
Guru 19785 points

Hi Team,

Could you please tell us how to treat the following unused pins to have best performance ?

Pin8 IN1+ : Connect to GND through 4.7uF cap ?
Pin9 IN1- : Connect to GND through 4.7uF cap ?

Pin22 OUT1- : Leave floating ?
Pin23 OUT1+ : Leave floating ?

Best Regards,

Kawai

  • 0
    TI__Intellectual 1705 points

    Hi Kawai-san,

    Input (IN1+/-) pin 8 and 9 can be left open (no connect) because when IN0+/- is selected, the unused IN1+/- is ignored.

    Also the unused output (OUT+/-) put can be left open (no connect) and it should be powered down (disabled).

    Regards,

    Michael

  • 0 in reply to Michael Hinh
    Guru 19785 points
    Hello Michael-san,

    Thank you for the answer.

    Would it be OK to connect as below or should we leave open ?

    Pin8 IN1+ : Connect to GND through 4.7uF cap
    Pin9 IN1- : Connect to GND through 4.7uF cap


    To minimize the cross talk inside the device, I thought it may be better to connect to GND or terminate with 50 Ohm, rather than leaving it open. What do you think ?

    Best Regards,
    Kawai
  • 0 in reply to Kawai
    TI__Guru* 93670 points
    Kawai-San,

    You can use 4.7uF Cap on Pin8 and pin9 as you noted. Please note you need to use 49.9 ohm in series with this Caps. This way you are terminating these pins. So you go from Pin8 to 4.7uF and then from 49.9 Ohm to GND. You should do the same thing for pin9 as well.

    Regards,,nasser
  • 0 in reply to Nasser Mohammadi
    Guru 19785 points
    Hello Nasser-san,

    I understand, thank you for your reply. I am thinking that it is better to have termination for the pins.

    Howeve, I would like to double check that if we can connect as following, as the IN1+/- could be left open.

    pin8/9--->4.7uF cap--->GND

    If there is some problem, I would need to inform customer to take 4.7uF and leave the pins open.

    Best Regards,
    Kawai
  • 0 in reply to Kawai
    TI__Guru* 93670 points

    Hi Kawai-San,

    I don't see a problem since IN1+/- are not going to be used. I would have preferred to have 49.9 Ohm resistors but if these are not possible this should be ok. Please make sure 4.7uF caps are very close to pins 8&9. 

    Regards,,nasser

  • 0 in reply to Nasser Mohammadi
    Guru 19785 points
    Nasser-san,

    Thank you very much for your advice.

    Best Regards,
    Kawai