CY7C63001C
CY7C63101C
and fall time of the signals on this cable are well controlled to
reduce RFI emissions while limiting delays, signaling skews
and distortions. The CY7C630/101C driver reaches the
specified static signal levels with smooth rise and fall times,
resulting in minimal reflections and ringing when driving the
USB cable. This cable and driver are intended to be used only
on network segments between low-speed devices and the
ports to which they are connected.
6.10
USB Physical Layer Characteristics
The following section describes the CY7C630/101C
compliance to the Chapter 7 Electrical section of the USB
Specification, Revision 1.1. The section contains all signaling,
power distribution, and physical layer specifications necessary
to describe a low- speed USB function.
6.10.1 Low-Speed Driver Characteristics
The CY7C630/101C devices use a differential output driver to
drive the Low-speed USB data signal onto the USB cable, as
shown in Figure 6-22. The output swings between the differ-
ential HIGH and LOW state are well balanced to minimize
signal skew. Slew rate control on the driver minimizes the
radiated noise and cross talk on the USB cable. The driver’s
outputs support three-state operation to achieve bidirectional
half duplex operation. The CY7C630/101C driver tolerates a
voltage on the signal pins of –0.5V to 3.8V with respect to local
ground reference without damage. The driver tolerates this
voltage for 10.0 µs while the driver is active and driving, and
tolerates this condition indefinitely when the driver is in its
high-impedance state.
6.10.2 Receiver Characteristics
The CY7C630/101C has a differential input receiver which is
able to accept the USB data signal. The receiver features an
input sensitivity of at least 200 mV when both differential data
inputs are in the range of at least 0.8V to 2.5V with respect to
its local ground reference. This is the common mode input
voltage range. Proper data reception is also guaranteed when
the differential data lines are outside the common mode range,
as shown in Figure 6-23. The receiver tolerates static input
voltages between –0.5V and 3.8V with respect to its local
ground reference without damage. In addition to the differ-
ential receiver, there is a single-ended receiver for each of the
two data lines. The single-ended receivers have a switching
threshold between 0.8V and 2.0V (TTL inputs).
A low-speed USB connection is made through an unshielded,
untwisted wire cable a maximum of 3 meters in length. The rise
One Bit
Time
(1.5Mb/s)
Signal pins
pass output
spec levels
with minimal
reflections and
ringing
VSE (max)
Driver
Signal Pins
VSE (min)
VSS
Figure 6-22. Low-speed Driver Signal Waveforms
1.0
0.8
0.6
0.4
0.2
0.0
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2
Common Mode Input Voltage (volts)
Figure 6-23. Differential Input Sensitivity Over Entire Common Mode Range
Document #: 38-08026 Rev. *B
Page 17 of 28
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