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Original question:

PCA9306: Questions of PCA9306

PCA9306: EN 200k Resistor

Naizeng Wang
Expert 5380 points
Part Number: PCA9306

Hi team,

Why we choose 200k EN pull-up resistor? Could you please share the consideration? 

  • 0
    Guru 316470 points

    That resistor limits the current that flows into VREF2 and out of VREF1, and is needed to drop the voltage between VCC1+Vgs and VCC2. 200 kΩ is a value that works for all valid combinations of VCC1 and VCC2. You could also use some other value that results in an IREF that is neither too small nor too large. (This is an analog circuit; there is no fixed limit.)

  • 0
    TI__Mastermind 47008 points

    Hi Naizeng,

    200k is a current limiting resistor limiting the current between VREF2 and VREF1 voltage supplies when the FET is ON. 200k resistor also sets the voltage bias of 1.8V + VTH so that level translation is possible. 

    Clemens is correct. 200k is not the only option. I have not personally tested this device in lab with another resistance outside what is listed in the datasheet, but I am sure some deviance from 200k is just fine. If changing the value of the 200k resistor is needed, it is always good to ensure that the VREF2 + EN voltage is still biased at VREF1 + VTH. 

    Regards,

    Tyler