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PCA9306-Q1: PCA9306TDCURQ1

Part Number: PCA9306-Q1

I2C BUS translator PCA9306-Q1, VREF2 pullup 200k, if 5V change to 3.3V level, VREF1=3.3V, VREF=5V, use Equation 6 calculated Rmin = (5-3.3-0.6)/0.128 = 8.6k, but usually 200K is used. How to explain? or 10k is enough.

  • Using a smaller resistor would work, but would not improve anything, it would just wastes power, and the power supply connected to VREF1 must be able to sink that current.

  • So, 200k is an universal using. 1.8V to 3.3V can use 200k, 3.3V to 5V can use 200k too?

    Other question VREF2 need 100pF capacitor, why it's 100pF? 

  • So, 200k is an universal using. 1.8V to 3.3V can use 200k, 3.3V to 5V can use 200k too?

    Other question VREF2 need 100pF capacitor, why it's 100pF? 

  • Yes, 200 kΩ works in all situations.

    The capacitor at VREF2 is optional, and can have any value. A larger value removes more noise, but takes longer to charge at power up (because it is charged through the resistor).

  • The 200k resistor works for all voltages like clemens has pointed out. Adding a capacitor on EN helps to stabilize the voltage since it is used to pass a reference voltage to the pass FET gates. Sometimes fast fall times and close traces can affect the EN voltage so adding cap can help but also influences the power up sequence. Making the 200k resistor lower burns through more power but does provide better bias to the EN though in most cases, it is not needed. (I've only seen one case since supporting this device where using a lower resistor was required....)