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Design >> High-Speed I/O Design >> USB 1.1 PHY Speed Control
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Message started by qiushidaren on Jul 6^th, 2010, 7:28pm

Title: USB 1.1 PHY Speed Control
Post by qiushidaren on Jul 6^th, 2010, 7:28pm

Hi all,

I am studying USB 1.1 PHY IC design now, but the speed control confuses me. I am modifying another guy's circuit, in this circuit, the part of speed control doesn't get an op amp to control the rise and fall times, it just uses the speed control pin to open or close an NMOS connecting to an inverter by a res and a PMOS connecting to an inverter by a res. Could anyone give me some suggestions about this?

-Terry

Title: Re: USB 1.1 PHY Speed Control
Post by casual on Jul 7^th, 2010, 1:07am

The res is to meet the termination spec, around 40-45ohm.
Is the control pin controlling the predriver or driver?