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PCA9306-Q1: Leakage from VREF2 region to VREF1 region when VREF1 is turned off

NOBUO FUJIHARA
Expert 8265 points
Part Number: PCA9306-Q1

Hi team,

My customer asks question below, could you support this?

There are intermediate voltage on signal node in VREF1 region, under below condition.

- VREF2 is supplied and EN=ON, 

- VREF1 is OFF

With above supply condition, is there current flow from VRFE2 region to VREF1 region which can generate intermediate voltage?

Best regards,

  • 0
    TI__Guru 62910 points

    Hello Fujihara-san,

    Yes, there will be a small current flow from VREF2 to VREF1.  The voltages at pins 7 (VREF2) and 8 (EN) will typically be about 0.6 V above the voltage at VREF1, and you could compute the current flowing in your case as (3.3 V - VREF2) / 200 kOhm.  If nothing on the VREF1 rail is able to sink this current, a voltage increase on VREF1 could be observed.  If this is not desired, a pull-down resistance could be placed on VREF1 in order to sink the current.

    Alternatively, the EN pin could be pulled up to VREF1 instead.  This would change the switching behavior of the device to lower the turn-on voltage (i.e., the switch channels would not conduct until a voltage of ~1.2 V is present at either side).  This could result in some increases in signal transition times, but I would expect I2C communication to remain functional in most cases.

    Regards,
    Max

  • 0 in reply to Max Robertson
    TI__Expert 8265 points

    Hi Max-san,

    Thanks a lot for prompt support.

    I shared the information and re-visit when customer has further question.

    Best regards,