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Circuit Description
NEC-FA150ATUA
11. USB circuit
11.1 USB description
The USB IC AT43301 (I201), port 0 (pin 14, 15) is a full speed port. A 1.5K ohm (R201) pull-up resistor to the
3.3V regulator output CEXT (I201, pin 3) is required for proper operation. the downstream ports support both
full-speed as well as low-speed devices, 15K ohm (ex. R217) pull down resistors are required at their input (I201
pin 16 ~ pin 23). Full speed signal requirments demand controlled rise/fall times and impedance matching of the
USB ports to meet these requirements 22 ohm (ex: R209) resistor must be inserted in series between the USB
data pins (I201 pin 14 - pin 23) and the USB connectors.
Note:OVC. The overcurrent signal control circuit (D201, Q201, Q205) is read through the I201 pin 9. A logic
low at OVC is interperted as an overcurrent condition. This could be caused by an circuit overload, or a short
states.
11.2 USB hub control circuit
I203 is a reset IC, and I201 is a USB hub control IC made by ATMEL.
NOTE: When the monitor power circuit is turned on, a 5V power is fed to I203. Upon the detection of about 4.
5V, I203 begins to generate a reset signal of 450msec. Than control Q204 to turn on Q203 input Vcc to I201when
I201 enables communication with a higher port when UD+ and UD- from the USB connector are applied to pin
14 and pin 15, respectively. Pin 16, 17, 18, 19, 20, 21, 22 and 23 are connected to the USB connector of the lower
port. They function as a communication interface between lower and higher ports. If an overcurrent is generated
in the lower port, it is transferred to the higher port.
X201 is a crystal oscillator that supplies a 6MHz clock signal to the USB hub control IC (I201).
11.3 Lower port circuit
J203, J204, J205 and J206 are the USB lower-port connector.
The 5V output from the power supply passes through the poly-switches of R202, R205, R206 and R225, and is
led to the power supply pins (pin 1 of each connector) of the USB lower-port connector.
An overcurrent signal is given from the poly-switch - USB lower-port connector line to I201 overcurrent has
been generated in the lower port.