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ADT7420 question about pull-up resistors!

jgirgis

Hi 

I am making a board that has the ADT7420 on it.

I want it to be the slave device my master device to be many meters away.

  1. Where do I put the pullup resistors? On the master or slave board?
  2. For the CT and INT pins are the pullups optional?
    1. If not, is it best to put their pull ups on a master or slave board?
  3. For decoupling many meters away should I have a low pass filter?
  4. For the i2C communication pins could I have resistor terminations for the wires that are up to a meter away? Will that interfere with the pullups?

Thanks

  • +1
    •  Analog Employees 
    on Oct 25, 2021 8:44 AM

    Hi,

    See answers below:

    1. It's advisable to put the pullup resistor near the master just in case the cable might be disconnected. 

    2. INT and CT pins are open-drain output, thus they both require a 10kohm pull up resistor to VDD. Make sure that ADT7420 is fully powered up to VDD before reading INT and CT data.

    3. Decoupling cap must be placed as close as possible to minimize the line inductance between the decoupling cap and device.

    Can you share your schematics and the application you are trying to do here??

    Regards,

    Marymae