[SI-LIST] usb eye pattern tuning
- From: Li Hui <lihuizju@xxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Wed, 16 Jan 2013 14:11:54 +0800
Hi Experts:
we are making a device which has an USB 2.0 port. This port is consisted of
two part of traces, one is on the main board(about 100mm), the other one is a
FPC(about 120mm) who has an micro usb receptacle on it. We are using a pair of
connectors to connected them togother. Unfortunately during the USB compliance
test, we find the rising and falling edges of the signal are too long which
violated the test. We checked our layout, the differential trace impedance on
main board is 87 ohms, and they are protected well which means they are
surrounded by gound stearoly. FPC's impedance seems good too, little larger
than 90 ohms. We changed the settings in processor such as slew rate, setup and
hold time, and terminated impedance. But can't find a set of paraneters which
could pass the test.
So can any one help to give us some advices which can improve the signal
quality? We know the shorter the length of trace can help, but the ID has been
decided, it can't change now.
Besr
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