PCA9306: PCA9306 in switch configuration while Vref1 = Vref2

KuanChieh Chen

Part Number: PCA9306
Other Parts Discussed in Thread: SN74LVC2G66

Hi,

We would like to have a design with several devices on the same I2C buses. those devices might be powered by either 3.3V standby power or 3.3V normal power.

To avoid voltage conflict and current leakage, we would like to put PCA9306 as a buffer.

Since both voltage levels are 3.3 volt, we follow Figure 10 in the datasheet. In this figure, the EN pin is controlled by GPIO(we would like to connect it to normal power good)

We notice it claim "GPIO: high logic does not exceed Vref2 + Vth". However, in 9.2.1, the EN is required no less than Vref1 + Vth.

Looks these two statements are in conflict when Vref1 = Vref2. Do you have any suggestions? thanks

Best,

over 4 years ago

+1 Clemens Ladisch over 4 years ago

Guru 316940 points

The Vref1 = Vref2 application is a special case in which the reference transistor is not used and some of the other restrictions do not apply. To understand why, see the explanations referenced by [FAQ] How do the LSF translators work?

The PCA9306 is not a buffer but a passive switch.

If you just want to be able to disconnect bus segments, use a smaller and cheaper switch like the SN74LVC2G66.

0 Eric Hackett over 4 years ago in reply to Clemens Ladisch

TI__Guru 74262 points

Thanks for the help Clemens!

KC,

Please let us know if you have any other questions.

Regards,

Eric Hackett

Interface

Interface forum

PCA9306: PCA9306 in switch configuration while Vref1 = Vref2