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USB hosts hubs transceivers Forum Discussions

TeMa_2997106
Level 6
Level 6
10 likes received 10 solutions authored 250 replies posted

When powering up HX2VL, a waveform that looks like DP is slightly pulled up is observed.

HX2VL_DP_Pullup.png

Why is this happening? Is there any problem with this behavior according to the USB standard?

Thanks,
Tetsuo

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2 Replies
TakashiO
Moderator
Moderator
Moderator
100 sign-ins 50 replies posted 25 solutions authored

Hi @TeMa_2997106 ,

Thank you for posting into our community.

Could you tell me which pin(D or DD) did you see the positive pulse at start up timing?
Also, could you tell me if you plan to use the device as bus power app no not?

There is internal 1.5k ohm pull-up resistor at DP, upstream line. It is pulled-up to 3.3V rail and ON/OFF by internal switch. 

Regards,

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TeMa_2997106
Level 6
Level 6
10 likes received 10 solutions authored 250 replies posted

This waveform was observed at the DP pin (not DD pin).

Power mode is self-powered mode. Power is supplied from DCDC on the board. HX2VL is always ON when the system is ON.

Thanks,
Tetsuo

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