TPS254900-Q1: Compliance with BC1.2 Ground Offset High Speed and Full Speed Testing

Hi Becker,

The TPS254900-Q1 been  test the BC1.2 CDP in the USB2.0 high speed and we don't  have  the certification issue in our  mass customer .

I am not very clear the Ground offset test ,is it the new test item in  the CDP test?  Do you know  the detailed test setup ? I assume to add some voltage in  Ground to check the CDP handshake is success or not ,right ?

Hi Michael,

Thanks for the insight! The Ground Offset Test can be found in the BC1.2 Specification. I have placed the Full Speed section below:

Has your team tested the TPS254900-Q1 under this condition?

Thanks,

Jared

Hello Jared,

I am not  sure  we have  test this standard before,  have  you met the test issue  in your project  ?

Michael.tan

Hi Michael,

Yes, there is a possible test issue in my project. Would it be possible for your team to run this test on your bench for full speed and high speed?

Thank you,

Jared

Hello Jared,

I have  discuss with our team member who know more about this  test .

The CDP Ground offset  test is a system test not a silicon device test. 

According to the test  item from 1 to 6 is  to verify the port  whether can complete CDP handshake. The item 7~11 is add offset to ground to verify the system soc response. In the  7~11 step the TPS254900-Q1 only bypass the DP and DM to the Soc , so it should not be the device  issue in these test.

Do you know which step you have fail in your test  ?

Hi Michael,

You are correct about the CDP Ground offset test being a system test. However, I think all the tests in BC1.2 are system level tests, correct? Are there any silicon device level tests in BC1.2?

The failure is at step 9, the reset and enumeration after applying to 0.375V offset. Is there a good way to check to make sure that DP and DM are passing the signal correctly?

Thanks for your help on this Michael!

Jared

Hello Jared,

The TPS254900-Q1 in BC1.2 test is Pass in our most of customer. When the device be set at CDP mode the DP and DM will data switch will keep turn on to by pass the data. You can use the multimeter to test the DP/M_IN and DP/M_OUT to check the data switch whether turn on in your test.

I am assume the ground layout is not good for this case, maybe have noise in your data ground or the data ground trace too small to create an equivalent resistance in high current charge situation..

Hi Michael,

Thank you for following up! I will reach out to you offline to discuss.

Thanks,

Jared