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AMC7836: Can AMC7836 reset pin pull down to GND?

Zhizhao Niu
Intellectual 2435 points
Part Number: AMC7836

Hi Team, 

I have one question about the AMC7836 reset pin connection with MCU. I found in all reference design the Reset pin is pull up to IOVDD with ~kohm resistor. I want to know can I pull down the reset pin as below? 

  • The advantages of this connection is that if MCU power up late than AMC7836, the AMC7836 will stay in reset mode. This can meet the requirement that device need to stay in reset state until all supplies reach the power-good threshold.

Is there any risk to pull down reset pin to GND? 

Thanks. 

B.R.

Zhizhao

  • +1
    TI__Prodigy 190 points

    Hey Zhizhao,

    For the application you describe, there should be no risk with using a pull down resistor on the reset pin. However, please do keep the following in mind

    1)  You must select the value of resistance appropriately. Use the datasheet for your MCU to find the maximum low-level  output voltage (Vol) and the minimum high-level output voltage (Voh) for the GPIO connected to the AMC7836 RESET, as well as the minimum and maximum GPIO output current (Imin and Imax respectively). Ensure that the resistance value R is high enough to ensure Vol - (Imin*R) is less than 0.45 (the maximum voltage that can be read as logic low by the AMC7836). Conversely, check that your resistance value is not too high; a very high R value will cause your RESET pin to be stuck at logic low (specifically, if Voh - (Imax*R) is less than 0.7*IO_VDD, where IO_VDD is measured on the AMC7836)

    2) As noted in section 9.1 of the datasheet, the AMC7836 device includes a power-on reset (POR) and following a reset communication with the device is valid only after a 250 µs power-on reset delay. This is likely sufficient to ensure that the device is in a reset state long enough without needing to hold the pin low.