TUSB544: LFPS Vtx-DIFF-PP failure

Antony Lin

Part Number: TUSB544

Hi,

We're using TUSB544 at a type-c port under I2C mode controlled by PD controller. We currently failed USB3.1 compliance test for the item as shown below (other items are passed.)

Currently USB3 gain is configured as below

0x20 register configured as 0x11
0x21 register configured as 0x11
LFPS_EQ bit is set to '0'.

Please suggest what is the next step to debug on this issue. Thanks!

Antony

over 5 years ago

0 Malik Barton57 over 5 years ago

TI__Guru 64326 points

Hi Anthony,

Could you also share the waveform with respect to this failure? I recommend first connecting the USB test fixture and then start the LFPS test. When you start the test before inserting the test fixture there can a large shift in common mode voltage as test fixture is inserted.

0 Brian Zhou over 5 years ago

TI__Guru**** 158705 points

what is your setting of CFG?

0 Antony Lin over 5 years ago in reply to Brian Zhou

TI__Genius 13480 points

Hi Brian,

0x0C register ix configured as 0x58.

Thanks,

Antony

0 Malik Barton57 over 5 years ago in reply to Antony Lin

TI__Guru 64326 points

Hi Anthony,

To lower VOD setting please configure register 0x0C as 0x44.

0 Antony Lin over 5 years ago in reply to Malik Barton57

TI__Genius 13480 points

Hi Malik,

0x44 can fix this issue. Thanks.

Antony

0 Antony Lin over 5 years ago in reply to Antony Lin

TI__Genius 13480 points

Hi Malik,

There's another project facing similar issue, and I try to change register setting as the same way above to modify VOD setting from 1100mVpp to 900mVpp. It improves, but not enough. (Please see corresponding results as below.) What else can we configure to improve this?

1100mVpp:

900mVpp:

Thanks,

Antony

0 Malik Barton57 over 5 years ago in reply to Antony Lin

TI__Guru 64326 points

Hi Anthony,

LFPS swing is controlled mainly by USB Host. TUSB544 can only influence the LFPS Vpp to a certain point. You can try reducing the DC gain as well (0x0C = 0x48) This may help with the test here. Customer should try reducing LFPS swing on the host side as well.

Interface

Interface forum

TUSB544: LFPS Vtx-DIFF-PP failure