P82B715 and PCA9306 power consumption figures needed

Hello David,

I have a few questions.  

1)  Why would the customer use the P82B715 if they are only using 2k pull ups???  The P82B715 is designed for stronger pull down strength and overkill for pull-up's of 2k.  Do you have any information about the specifics of the application?  Data rate, cable capacitance, operating voltage range?  

2)  Did you first do a search on the E2E to see if the answer to your question was already answered in some other post?

E2E is a powerful tool for finding answered to commonly asked questions.  In order to make the most efficient use of the forum we ask that users do a search before posting to the forum.  This reduces the number of duplicate posts and helps make a more efficient forum.  

For example, I simply typed into the search bar "PCA power consumption" and you will get an array of posts related to your question.  You may have to open up a few posts to see the post that most closely answers your questions, but generally speaking you will get your answer much faster than waiting for our response.  If you don't find the desired post than by all means please post the question directly.  

When posting directly please try and include as much information as possible.  For this forum many of the typical parameters that help us answer questions efficiently are as follows:

Supply Voltage: Nominal Operating Voltage and Voltage Range

Data Rate / Operating Mode: Standard Mode, Fast Mode, Fast Mode+, or something in-between

Load: Capacitive Load

Application: I/O Expander, Translation/Level Shifting, Buffer, Switch?

Key Requirements:  Low Power (Battery Application), Hot Plug, I/O's needed, Switch Configuration, etc.

I have taken the liberty to do the research for you and here is a post that directly answers your question about PCA9306 power consumption.

https://e2e.ti.com/support/interface/i2c/f/390/p/322334/1166536#1166536

If you need clarification or help, please feel free to post on E2E and we will do our best to answer it in a timely manor.

Sincerely,

-Francis Houde

Thank you for your questions and suggestions.

Regarding item 1, I will ask about his data rate, cable capacitance, etc. The voltage for the P82B715 is 3.3V as noted. You've mentioned that the P82B715 is overkill for 2K pull-ups. What alternative device would you recommend as an I2C bus extender that would not be overkill? The P82B715 product page doesn't show any other parts for comparison. The master selection guide at this link also doesn't list output sink current (pull-down strength) for comparison; only capacitive loading - and almost all devices are shown for 400pF loads:
www.ti.com/.../i2c-hub-buffer-repeater-products.page

Regarding item 2, I should have reviewed the E2E postings. The link you provided for the PCA9306 is very helpful - thanks.

David

Hello David,

I have put a link to the I2C selection guide.  See section 4 - I2C Buffers, page 8.

http://www.ti.com/lit/an/slva787/slva787.pdf

Depending on the voltage rail they need to support, speed of I2C, and amount of capacitance needed to be supported you will be able to select a device.  Based on limited information you gave me I think that the TCA9617A might be a good choice.   

-Francis Houde

Francis,

I just received word that this customer's design is a refresh of a current design, where the P82B715 is re-use of a previous design that works fine, so he is confident in using it.  The interface goes from one card to another across a backplane of ~12 inches.  The rate is 400kHz (standard mode).  The customer will use the 22mA typ / 35mA max for his power estimate.  Thanks again for the link related to the PCA9306 power consumption.  The customer is reviewing that info.

For now, the customer appears to be satified.

Thanks!

David Hildebrand