PCA9306-Q1: PCA9306TDCURQ1

songlin he

Part Number: PCA9306-Q1
Other Parts Discussed in Thread: PCA9306

How to explain this sentence as follows, if I2C from SOC(1.8V) to IC(3.3V), SOC I2C is open drain, but IC's I2C is LVTTL, not open drain, how to confirm the direction? If use PCA9306 is not fine?

"However, if either output is totem-pole, data must be unidirectional or the outputs must be 3-stateable and be controlled by some direction-control mechanism to prevent high-to-low contentions in either direction."

over 1 year ago

0 Clemens Ladisch over 1 year ago

Guru 243870 points

I²C always is open drain. "LVTTL" probably refers only to the allowed voltage levels.

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

Prodigy 60 points

What's this means?

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

Guru 243870 points

The PCA9306 creates a direct connection between the pins on both sides. If the other two devices drive the line to opposite voltages, then there is short between VCC and GND, and all three devices could be damaged by the current.

This does not apply to I²C, because all I²C signals are open drain.

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

Prodigy 60 points

For this design, I2C from SOC(1.8V) to IC(3.3V), SOC I2C is open drain, but IC's I2C is LVTT, which level shift could be recommended to replace PCA9306？

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

Guru 243870 points

LVTTL does not imply totem pole or push/pull. Please show where we can find the datasheet of that IC.

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

Prodigy 60 points

Sorry, it's a internal datasheet. I'll check with the vendor.

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

TI__Mastermind 49270 points

Songlin,

Technically the PCA9306 device can accept push pull architectures. The device is mainly a pass FET so you could use push pull on it, the downside is the side receiving the signals from the push pull structure may not see the VoH levels, it would likely see Vg-Vth (in a translation set up for the device, it would be Vref1 voltage). If an external pull up is on the line, then it may get pulled up by depending on the frequency and loading of the bus the ViH level could potentially be missed in the worst case where the push pull is on side 1 and vref2 is 5.5V and Vref1 was much lower.

-Bobby

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PCA9306-Q1: PCA9306TDCURQ1