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PCA9306-Q1: Supply current

Arie Li
Expert 3390 points

Part Number: PCA9306-Q1
Other Parts Discussed in Thread: PCA9306,

Hi experts,

A question need your help. What's the supply current of PCA9306-Q1? I didn't find this spec in datasheet. For below application, how many current does PCA9306 need from the 3.3V and 5V supply rail respectively? Thanks.

  • 0
    TI__Guru* 79531 points

    Hey Arie,

    The supply current (or quiescent current) of this device can be estimated in the commercial datasheet for this device in section 8.1.8 in which we call it Ibias.

    In your set up, if you have 5V and 3.3V with a 200k ohm resistor then the biasing current is (5V-3.9V)/200k = 5.5uA.

    Be aware that the current is flowing from the 5V rail into the 3.3V rail, so if the 3.3V rail cannot handle this current (like if it were sourced from an LDO) then you could make the LDO unstable and lose regulation. This is described in section 8.1.7 of the commercial datasheet.

    I've tried to push these changes to the automotive version of the datasheet but it looks like it has not made it through yet.

    -Bobby

  • 0 in reply to BOBBY
    TI__Expert 3390 points

    Hi Bobby,

    Thank you very much for your detailed reply. If Vref1 is powered by Buck converter, should I add a pull down resistor at Vref1 pin?

    Arie

  • 0 in reply to Arie Li
    TI__Guru* 79531 points

    I do not know how your Buck Converter is regulating it's output so I can't be 100% sure but my guess is that a switching regulator like a buck should be able to sink some amount of current and regulate itself (to a degree). I would just add a DNP pull down resistor just incase you do see the buck regulator lose regulation.

    -Bobby