FT245BL USB FIFO ( USB - Parallel ) I.C.
3.0
Block Diagram ( simplified )
VCC
Send Immediate / WakeUP
PWREN#
3V3OUT
3.3 Volt
LDO
Regulator
FIFO Receive
Buffer
128 Bytes
USBDP
USBDM
USB
Transceiver
Serial Interface
Engine
( SIE )
USB
Protocol Engine
FIFO
Controller
D0
D1
D2
D3
D4
D5
D6
D7
RD#
WR
RXF#
TXE#
USB DPLL
FIFO Transmit
Buffer
384 Bytes
XTOUT
3V3OUT
48MHz
XTIN
GND
TEST
6MHZ
Oscillator
x8 Clock
Multiplier
12MHz
RESET#
RESET
GENERATOR
EEPROM
Interface
EECS
EESK
EEDATA
RSTOUT#
3.1
•
3.3V LDO Regulator
The 3.3V LDO Regulator generates the 3.3 volt
reference voltage for driving the USB transceiver
cell output buffers. It requires an external
decoupling capacitor to be attached to the 3V3OUT
regulator output pin. It also provides 3.3V power to
the RSTOUT# pin. The main function of this block
is to power the USB Transceiver and the Reset
Generator Cells rather than to power external logic.
However, external circuitry requiring 3.3V nominal
at a current of not greater than 5mA could also
draw its power from the 3V3OUT pin if required.
USB Transceiver
The USB Transceiver Cell provides the USB 1.1 /
USB 2.0 full-speed physical interface to the USB
cable. The output drivers provide 3.3 volt level slew
rate control signalling, whilst a differential receiver
and two single ended receivers provide USB data
in, SEO and USB Reset condition detection.
Functional Block Descriptions
•
USB DPLL
The USB DPLL cell locks on to the incoming NRZI
USB data and provides separate recovered clock
and data signals to the SIE block.
6MHz Oscillator
The 6MHz Oscillator cell generates a 6MHz
reference clock input to the x8 Clock multiplier from
an external 6MHz crystal or ceramic resonator.
x8 Clock Multiplier
The x8 Clock Multiplier takes the 6MHz input
from the Oscillator cell and generates a 12MHz
reference clock for the SIE, USB Protocol Engine
and FIFO controller blocks. It also generates a
48MHz reference clock for the USB DPLL.
•
•
•
DS245BL Version 1.7
© Future Technology Devices Intl. Ltd. 2005
Page 5 of 24
FTDI [ FUTURE TECHNOLOGY DEVICES INTERNATIONAL LTD. ]
