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PCA9306 / Is there any leak path from VREF2 to VREF1?

K.Yaita
Guru 29720 points
Other Parts Discussed in Thread: PCA9306

Hi Team,

My customer designs PCA9306 as the following schematic.
When he supplied VREF1=1.8V and V_DPU=4.4V, then he saw VREF1 increased up to 1.9V although supplied 1.8V.
The issue doesn't occur when he doesn't supply V_DPU.

Is there any leak path from VREF2 to VREF1?




Best Regards,
Yaita / Japan disty

  • 0
    TI__Genius 16510 points

    Yaita-san,

    Yes, there is a leakage path between the two rails. It is not actually leakage, but intended device operation.

    The biggest contributor to such behavior (the VREF1 rail increasing) is 1 of 2 reasons:

    1) There is no 200k pull-up resistor or it's in the wrong location and not connected to the correct rails (see below picture)

    If the value is too low, you will increase the current that flows from VREF2 pin to VREF1. This is why we recommend 200k.

    2) Your VREF1 power supply is unable to sink any current. In this case, you may need to put a bleed-off resistor on the VREF1 rail to ground, enough to bleed the extra current off. A ~300k ohm resistor between VREF1 and ground should be enough to bleed the current without wasting too much.

  • 0 in reply to Jonathan Valdez
    Guru 29720 points

    Hi Jonathan-san,

    I appreciate for your quick support!
    My customer put appropriate 200kΩ, so I think 2) should be considered.
    I will inform the content to him.

    Best Regards,
    Yaita