• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 32 subscribers
  • Views 1111 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Using PCA9306 for OMAP3503 application and I notice the PCA9306 is dumping 21- 27ma current into the 1.8V rail

Lance Forman
Prodigy 10 points
Other Parts Discussed in Thread: PCA9306, OMAP3503, TPS65920

We are using two PCA9306 devices for I2C level translation on OMAP3503 application and I notice the PCA9306 is dumping 21- 27ma current into the 1.8V rail.

It is translating from 1.8V logic to 3.3V logic.

I have 1.1K pullup on SDL and SDA lines to 3.3V and 4.7K pulllup on the 1.8V logic side.

I have confirmed that current is flowing apparently from the 3.3V rail to the 1.8V rail this by lifting the Vref1 pin and measuring the current and noticing it is traveling from the chip back to 1.8V. I have disconnected the IC's on the 3.3V side of the SDA and SCL so there is only the resistor pullups. I ahve verified the resistance values of the pullups

 

This causes a problem for the switching power supply when the system is beginning to come up since the power draw on the 3.2MHZ swticher on TPS65920 is much less than 21 ma when first powering up. This causes the power supply to rise to over 2.0V.

Any thoughts why the PCA9306 would be dumping current to the 1.8V rail?

 

  • 0
    Prodigy 30 points

    Have you made sure you haven't connected the Vref2 pin directly to the 3.3V supply?

    It looks unusual in the data sheet but it is correct to connect the reference via a resistor as well as the enable pin.

    If you're still having problems perhaps you need to change the value of the resistor feeding the Vref2 pin?