PCA9306-Q1: PCA9306TDCURQ1

songlin he

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.

over 1 year ago

0 Clemens Ladisch over 1 year ago

Guru 244360 points

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.

0 songlin he over 1 year ago in reply to Clemens Ladisch

Prodigy 60 points

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?

0 songlin he over 1 year ago in reply to Clemens Ladisch

Prodigy 60 points

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?

+1 Clemens Ladisch over 1 year ago in reply to songlin he

Guru 244360 points

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).

+1 BOBBY over 1 year ago in reply to songlin he

TI__Mastermind 49410 points

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....)

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PCA9306-Q1: PCA9306TDCURQ1