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LP8860-Q1: leakage current of EN pin

K.Hamamoto
Guru 12155 points
Part Number: LP8860-Q1

Hi

Our customer are evaluating LP8860-Q1. And they found some leakage current of EN pin when the pull down resistor is connected to EN pin.

(That was about 130uA.)

On their configuration, the VDDIO/EN pin is tied to ground via pull down resistor and also connected to MCU (to GPIO pin for controlling by enable signal). 

Until controlling by MCU which is started up, they would like LP8860 to be disable. That is why they put the pull down resistor(10kohm) to EN pin.

However the voltage of EN pin exceed the threshold voltage by that leakage current and LP8860 operate before controlling by MCU.  

How much we should set the value of pull down resistor? 

Regards,

Koji Hamamoto

  • 0
    TI__Prodigy 60 points

    Koji-san,

    Our engineers are out of office until Tuesday and will reply then, Just to clarify, is the 130 uA flowing through 10k resistor and exceeding the threshold at the EN pin? Do you have a diagram of the connection? Thanks,

    Regards,

    John Parry

  • 0 in reply to John Parry1
    Guru 12155 points

    Hi John-san,

    Thank you for your support.

    This is a diagram of the connection.

    There are same leakage current flawing through the pulldown resistor even if the MCU is removed.

    We need how we can set the pull-down resistor.

    Regards,

    Koji Hamamoto

  • 0
    TI__Expert 4565 points

    Hi Hamamoto-san,

    I believe that FAULT pin of LP8860 is pulled up to VDD, not to EN/VDDIO.

    LP8860 has an internal ESD structure forms body diode between FAULT and EN/VDDIO, so if FAULT pin is pulled up to VDD, EN/VDDIO will be pulled high depending on pull up resistor when VDD goes high. If you can't change pull up of FAULT to EN/VDDIO on PCB, you will need to use smaller value of pull down resistor to lower EN/VDDIO level even with higher leakage. 3.3kohm will cause ~200uA leakage, but it will be low enough to make EN/VDDIO low level.

    Please send me an email, if you have a further question. sungho.yoon@ti.com

    Thanks,