PCA9306: Signal ports(SCL2,SDA2) can be applied by +3.3 Volt when not supplying power(=0 Volt)

user1367489

Part Number: PCA9306

I would like to know that if the signal ports(SCL2,SDA2) can be applied by +3.3 Volt when not supplying power(=0 Volt) on PCA9306.

Thank you.

over 2 years ago

0 Clemens Ladisch over 2 years ago

Guru 317250 points

The PCA9306 does not have power supply pins; the VREF1/2 pins just bias the internal transistors. During normal operation, a current flows between VREF2 and VREF1.

To ensure that the I/O pins are high impedance, the EN pin must be at GND. If you actively drive EN to GND, you must do this with an open-drain driver.

See [FAQ] How do the LSF translators work?

0 BOBBY over 2 years ago

TI__Guru 73591 points

As Clemen's pointed out, the device doesn't need to the power supply pins to be biased. This means as long as the EN pin (generally tied to VREF2) is GND, the device will be high impedance.

user1367489 said:
I would like to know that if the signal ports(SCL2,SDA2) can be applied by +3.3 Volt when not supplying power(=0 Volt) on PCA9306.

Short answer: yes it is okay.

-Bobby

0 user1367489 over 2 years ago in reply to BOBBY

Prodigy 110 points

Thank you for your reply.

Sorry, I mistook power supply for VREF2 pin.

My understanding is below. Is it right?

---

It no damages with PCA9306 device that the signal ports(SCL2,SDA2) can be applied by +3.3 Volt when both VREF2 and EN pin are 0 Volt state.

0 BOBBY over 2 years ago in reply to user1367489

TI__Guru 73591 points

Correct, there is no concern in regards to damage if SDA/SCL pins are biased while Vref2/EN is GND.

-Bobby

0 user1367489 over 2 years ago in reply to BOBBY

Prodigy 110 points

Thank you very much for your reply promptly.

It is clear now.

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PCA9306: Signal ports(SCL2,SDA2) can be applied by +3.3 Volt when not supplying power(=0 Volt)