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PCA9306: PCA9306 Design Question :Vref2 Pull-up register

user5827344
Prodigy 110 points
Part Number: PCA9306


Hi, team.

I have any questions about PCA9306 .

＜Question＞

When using under the following conditions, can the pull-up resistor of Vref2 be used at 10kohm?

Vref1 : 1.8V , Vref2 : 3.3V

Best regards,

Yoshiaki.Tsujio

  • 0
    TI__Guru* 75871 points

    Hello Yoshiaki-san,

    Vref2>Vref1 so if you tie the enable pin to the Vref2 pin of the device like it is recommended in the datasheet, you will be using the device in translation mode. This means you will see about ~1.8V+0.7V at the enable pin. 1.8V+0.7V=2.5V Then the IoL into Vref2 to Vref1 will be (3.3V-2.5V)/10kohms. You have 80uA of current from doing this. If you had used a 200k resistor, you would see (3.3V-2.5V)/200kohms. This gives us around 4uA. This is 20 times the additional bias current, if you are okay with this then this is okay and will work. The only trade off is you will have a higher biasing current and a little more power dissipation.

    -Bobby