MC908JB16DWE Datasheet, PDF (178/332 Pages) Freescale Semiconductor, Inc – Microcontrollers

Universal Serial Bus Module (USB)
11.7.2.1 Output Driver Characteristics
The USB transceiver uses a differential output driver to drive the USB
data signal onto the USB cable. The static output swing of the driver in
its low state is below the V_OL of 0.3V with a 1.5kΩ load to 3.6V and in
its high state is above the V_OH of 2.8V with a 15kΩ load to ground. The
output swings between the differential high and low state are well
balanced to minimize signal skew. Slew rate control on the driver is used
to minimize the radiated noise and cross talk. The driver’s outputs
support 3-state operation to achieve bidirectional half duplex operation.
The driver can tolerate a voltage on the signal pins of –1.0V to 5.5V with
respect to local ground reference without damage.
11.7.2.2 Low Speed (1.5 Mbps) Driver Characteristics
The rise and fall time of the signals on this cable are greater than 75ns
and less than 300ns. The edges are matched to within ±20% to minimize
RFI emissions and signal skew.
USB data transmission is done with differential signals. A differential
input receiver is used to accept the USB data signal. A differential 1 on
the bus is represented by D+ being at least 200mV more positive than
D– as seen at the receiver, and a differential 0 is represented by D–
being at least 200mV more positive than D+ as seen at the receiver. The
signal cross over point must be between 1.3V and 2.0V.
ONE BIT
TIME
(1.5 Mb/s)
V_SE (max)
V_SE (min.)
V_SS
SIGNAL PINS
PASS OUTPUT SPEC
LEVELS WITH MINIMAL
REFLECTIONS AND RINGING
Figure 11-11. Receiver Characteristics
Technical Data
178
Universal Serial Bus Module (USB)
MC68HC908JB16 — Rev. 1.1
Freescale Semiconductor