PCA9306: Power on sequence (VREF1 and VREF2)

K.Hamamoto

Part Number: PCA9306

I read some E2E post as the following,

https://e2e.ti.com/support/interface/i2c/f/390/p/420667/1498896#1498896

However I do not understand which one of VREF1 and VREF2 should we startup first.

In our customer case, 3.3V (this should be VREF2) power on first, then after 10ms the 1.8V(this should be VREF1) start up.

Because the 1.8V is provided from 3.3V rail by DCDC.

Should we start up VREF1 first anyway?

Regards,

Koji Hamamoto

over 8 years ago

0 K.Hamamoto over 8 years ago

Guru 12155 points

Hi

Could you support for this post?

Regards,
Koji Hamamoto

0 Daniel R Noel over 8 years ago in reply to K.Hamamoto

TI__Intellectual 840 points

Hi Koji,

It is our recommendation that you start up Vref1 before Vref2, but there is no power sequence requirement for this part. That being said, no damage will occur to the device if you power it up the other way. If you power up Vref2 first you may see the low level on the Vref1 side propagate through to the Vref2 side. If your system can not handle this then you may want to implement the NMos solution in the post you linked.

Here is another post on this topic that may help also:
e2e.ti.com/.../1563337

Regards,
Daniel Noel

0 fhoude over 8 years ago in reply to Daniel R Noel

TI__Mastermind 23246 points

Hello Koji,
Please do NOT implement the NMOS solution in the previous post. That circuit will not work. I will correct the post later.

As long as you don't try to do I2C communications during the startup sequence than you should be fine either way that you power sequence.
-Francis Houde

0 K.Hamamoto over 8 years ago in reply to fhoude

Guru 12155 points

Hi Daniel-san,Francis-san,

Thank you for your support.

I understood there is no any sequence between VREF and VREF2.

Please correct me if my understanding is not correct.

Regards,
Koji Hamamoto

Interface

Interface forum

PCA9306: Power on sequence (VREF1 and VREF2)