USB Signal integrity

[usb2spy]

I am trying to do SI simulation for a high speed usb bus.
I have an MCU - SAM9G25 with high speed usb port and I need a receiver on the other side. I am not sure what to connect.

Can you guys help me with a host chip that has ibis model available.
For the time being I have connected a 90 ohm resistor across the D+/D- pins and 5pf cap to ground from both pins.

For high speed USB, do I need any pull up or pull down resistors?

[Jan Axelson]

See Chapter 7 in the USB 2.0 spec for electrical characteristics.

Actual devices need pullups and pulldowns because they connect at full speed before switching to high speed. Your simulation might be able to get by without them.

[usb2spy]

See Chapter 7 in the USB 2.0 spec for electrical characteristics.

Actual devices need pullups and pulldowns because they connect at full speed before switching to high speed. Your simulation might be able to get by without them.

Jan,

Initially even the high speed devices connect as Full speed, after that no pull ups are required on the D+/D- lines.
In fig.7-1 in the chapter 7, there are pull down resistors. The spec says they are required in downstream facing transceivers.
Downstream facing meaning a receiver?

[Jan Axelson]

Downstream means away from the host.

Downstream-facing transceivers are on host ports and on hub ports that connect to downstream devices. In other words, ports with A-series receptacles. The B-series receptacle on a hub is the upstream-facing port.

[usb2spy]

One more question about usb signal integrity. According to the usb 2 electrical specs(page135) -

the eye threshold levels for receiver without cable is +/-150mV (template4)
But with cable they are +/-275mV(template 3)?
Shouldn't the levels be less when a cable is being used, because of some cable attenuation?