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TPS22968: ON pin leakage when meeting specific condition

April Jiang
Intellectual 830 points
Part Number: TPS22968

  When set below condition including sequence, 

1. VIN & VBIAS  set 3v

2. ON2 set 3V, disconnect ON1 pin

3. VIN2 set 1.8V   ----> Seeing there's 700mv leakage on  ON1 PIN

Please help to check and give comments on " how this 700mv leakage happen" 

  • 0
    TI__Genius 15740 points

    Hi April,

    The datasheet for the TPS22968 specifically mentions the following statement with regards to the ON pin:

    "Active-high switch 1 control input. Do not leave floating"

    The ON pin does not have any pulldown that will keep the voltage at 0V. If not pulled down or pulled up, it may float up to an intermediate voltage, as seen in your scope shot.

    Thanks,

    Alek Kaknevicius

  • 0 in reply to Aleksandras_Kaknevicius
    TI__Intellectual 830 points

    Hi Kaknevicius,

           I have a question need to double confirm with you, now my customer uses an external circuit for ON pin.  I think there's risk in his circuit, and he could not get the result he want. Below are conditions, 

    1. PS-ON : 3V.

    2. VIN1 & VBIAS  set 3V

    3. ON2 set 3V 

    4. VIN2 set 1.8V  

    He wants to let ON1 pin as low level when PS_ON-R circuit is activated ( through resistor divide ). He set the Q2203B MOS close, and R2212 connect to GND. In this condition, he thinks the voltage on ON1 is 0.3V, but the voltage actually is 1.67v.  Could you please help to check if the connection circuit is ok for ON1 pin? Cause it is not in pull up status and not in pull down status too.

    Please comment here, Thanks.

  • 0 in reply to April Jiang
    TI__Genius 15740 points

    Hi April,

    The resistor divider should be putting ~0.27V on the pin, so it does seem odd that the customer is measuring 1.67V. The ON pin does not have any internal pullup or pulldown, so it can be considered high impedance and would not affect the resistor divider circuit. Has the customer confirmed that PS_ON_D is pulled down to GND and not an intermediate value?

    Thanks,

    Alek Kaknevicius

  • 0 in reply to Aleksandras_Kaknevicius
    TI__Intellectual 830 points

    Hi Kaknevicius,

       I have checked the PS_ON_D voltage, it is about 160mv, please see below pic for detail information, please help to check, it is odd that the resistor divider doesn't work. Thanks.

    A:  PS_ON_D : 160mv

    Gate : ~2.7V

    C : 1.66V