MC68HC08JB1 Datasheet, PDF (111/216 Pages) Motorola, Inc – Microcontrollers

9.7 Hardware Description
The USB module as previously shown in Figure 9-2 contains three
functional blocks: the low-speed USB transceiver, the USB control logic,
and the USB registers. The following details the function of the regulator,
transceiver, and control logic. See 9.8 I/O Registers for details of the
register settings.
9.7.1 Voltage Regulator
The USB data lines are required by the USB specification to have an
output voltage between 2.8V and 3.6V. The data lines also are required
to have an external 1.5kΩ pull-up resistor connected between a data line
and a voltage source between 3.0V and 3.6V. Figure 9-10 shows the
worst case electrical connection for the voltage regulator.
4.0V – 5.5V
3.3 V
REGULATOR
LOW-SPEED
D+
TRANSCEIVER
D–
USB DATA LINES
R1
USB CABLE
R1 = 1.5kΩ ±5%
R2 = 15kΩ ±5%
R2 R2
HOST
OR
HUB
Figure 9-10. Regulator Electrical Connections
9.7.2 USB Transceiver
The USB transceiver provides the physical interface to the USB D+ and
D– data lines. The transceiver is composed of two parts: an output drive
circuit and a receiver.
MC68HC08JB1 — Rev. 2.1
Freescale Semiconductor
Technical Data
111