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About ADP2138/39

Hi there,

I have questions about ADP2138/ADP2129.

Regarding, ENpin and Modepin, these pins have either internal pull up  or pull down?

If so, please let me know whether it is pull-up or pull-down ? 

Best regards,


  • Hi Hong,

    I checked the datasheet again, EN pin and MOtDE pin on Table5 say they should be connected to either Hi level or Low level. Please double check if they have internal pull down.

    If they have these pin are used as floating, right? 

    Best regards,


  • Hi Tarzan,

    Previously what I see in lab is that both EN and Mode pins are Low when they are left floating. 

    During the following  transient:

    EN HIGH --> EN floating,  EN pin voltage goes to low. Part was then disabled.

    Mode HIGH -->Mode Floating,  Mode pin voltage goes to low. Operates in PSM.

    I confirmed with the IC designer and there is no dedicated pull down resistor on the EN and Mode pins. If pins go low when floating then it is very likely the result of the leakage pull-down from the ESD device on the pins.

    If the customer is happy not being in control of the function of those pins then there is no harm in floating them. If there is high frequency noise coupling onto the pin traces then they could see the pins toggle high and low which may not be desireable. Really it’s up to the customer what they can live with.

    Could they place an external pulldown resistor on the pins?

    Best regards,


  • Hi Hong,

    Thank you for your answer! I understand what you mean.

    I will let our customer know that they should treat the pins as datasheet rec commended just in case.

    Best regards,