TUSB544: GPIO mode without connect AUX can't work DP

Bruce Lin_899

Part Number: TUSB544
Other Parts Discussed in Thread: TUSB1044

Hi Expert

After today's test, I ask customer direct connect SBU signal to TUSB544 AUX pin ( in orignial question we let AUX and SBU pin floating because QC SOC have SBU MUX by itself ) then DP can work.

But yesterday, David told me that can let AUX pin pull up or pull down. In this morning we use this suggestion, but it can't work.

So, my customer ask me how to explain why need to connect SBU signal to AUX pin and can't let it floating or pull up/down.

Thanks for reply.

Bruce

over 5 years ago

0 David (ASIC) Liu over 5 years ago

TI__Guru*** 140195 points

Bruce

When you bypass SBU/AUX, and pullup/pulldown on AUX, are you also driving CAD_SNK high?

Thanks
David

0 Bruce Lin_899 over 5 years ago in reply to David (ASIC) Liu

Intellectual 870 points

Hi David

TUSB544 don't have CAD_SNK ! TUSB546 have CAD_SNK!

0 David (ASIC) Liu over 5 years ago in reply to Bruce Lin_899

TI__Guru*** 140195 points

Bruce

Sorry for the typo. It is I2C_EN pin when it is floating. Otherwise if I2C_EN = 0, AUX snoop is enabled, and DP lanes are enabled depending on the DPCD register read.

Thanks
David

0 Bruce Lin_899 over 5 years ago in reply to David (ASIC) Liu

Intellectual 870 points

Hi David

Good news! The DP work at GPIO mode! Your answer let me to check the following spec.

In our schematics, we didn't connect SBU signal to TUSB544 and let I2C_EN be GND.

But TUSB544 seems will detect AUX Snoop( can you help describe what is this?) is present or not. So yesterday if we short SOC AUX signal to TUSB544 AUX pin, the DP works.

So today after your suggestion I ask customer make I2C_EN be floating, and Snoop function disable, the DP works without AUX signal.

Thank you very much for your time to help and suggestion (hint)!

Bruce

0 David (ASIC) Liu over 5 years ago in reply to Bruce Lin_899

TI__Guru*** 140195 points

Bruce

The AUX snoop is enabled when I2C_EN pin is pulled to GND. This is part of TUSB1044 power management feature. TUSB1044 will enable/disable DP lanes depending on the AUX traffic (with its AUX signals connected to the SBU/AUX bus). For example, if the source and sink only support 2 DP lanes, then TUSB1044 will only enable only 2 lanes.

When AUX snoop is disabled while in GPIO mode, then all 4 DP lanes are enabled regardless the AUX traffic between the source and the sink, and you do lose the power management feature.

Thanks
David

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TUSB544: GPIO mode without connect AUX can't work DP