TUSB1064: SBU and AUX common voltage level change when switching

Kairin

Part Number: TUSB1064

I am currently debugging some SOC design bugs which cause AUX communication error only when using with TUSB1064 together.

Now I found the SBU/AUX line common voltage is the key to reproduce the failure.

I want to understand what happens when TUSB1064 is switching and find a way to reproduce the failure without TUSB1064.

I captured the waveform when TUSB1064 is switching :

Could you tell me why SBU1 and SBU2 ascend to about 1.6V at first?

If I can get a block diagram describing SBU - AUX switching it helps a lot!

Thanks

over 2 years ago

0 Brian Zhou over 2 years ago

TI__Guru** 104105 points

Yu:

What waveform looks iike without TUSB1064?

Regards,

brian

0 Brian Zhou over 2 years ago in reply to Brian Zhou

TI__Guru** 104105 points

Yu:

Still need support?

Regards,

Brian

0 Kairin over 2 years ago in reply to Brian Zhou

Prodigy 110 points

Hi Brian

Sorry for the late reply.

With your advice I did some experiments and found after CTL1&FLIP inputted before the internal SBU⇒AUX mux is opened, the SBU1 and SBU2 seemed to be shorted together for a while, is that right?

Regards,

0 Brian Zhou over 2 years ago in reply to Kairin

TI__Guru** 104105 points

Kairin:

first SBU1/SBU2 are not shorted when SBU/AUX is opened.

for display port AUX channel, source side is weak pullup/pulldowm and sink side is strong pullup/pulldown. When SBU/AUX is opened, AUX+ suddenly get pulldown and AUX- got strong pullup and then change slowly due to capacitor.