DS245BQ Version 1.7

© Future Technology Devices Intl. Ltd. 2005

Page 9 of 24

FT245BQ USB FIFO ( USB - Parallel ) I.C.

POWER CONTROL GROUP

Pin#

Signal

Type

Description

10

PWREN#

OUT

Goes Low after the device is configured via USB, then high during USB suspend.

Can be used to control power to external logic using a P-Channel Logic Level

MOSFET switch. Enable the Interface Pull-Down Option in EEPROM when using

the PWREN# pin in this way.

11

SI / WU

IN

The Send Immediate / WakeUp signal combines two functions on a single pin. If

USB is in suspend mode (PWREN# = 1) and remote wakeup is enabled in the

EEPROM , strobing this pin low will cause the device to request a resume on the

USB Bus. Normally, this can be used to wake up the Host PC.

During normal operation (PWREN# = 0), if this pin is strobed low any data in the

device TX buffer will be sent out over USB on the next Bulk-IN request from the

drivers regardless of the pending packet size. This can be used to optimise USB

transfer speed for some applications. Tie this pin to VCCIO if not used.

MISCELLANEOUS SIGNAL GROUP

Pin#

Signal

Type

Description

4

RESET#

IN

Can be used by an external device to reset the FT245BQ. If not required, tie to

VCC.

5

RSTOUT#

OUT

Output of the internal Reset Generator. Stays high impedance for ~ 5ms after

VCC > 3.5V and the internal clock starts up, then clamps its output to the 3.3V

output of the internal regulator. Taking RESET# low will also force RSTOUT# to

drive low. RSTOUT# is NOT affected by a USB Bus Reset.

27

XTIN

IN

Input to 6MHz Crystal Oscillator Cell. This pin can also be driven by an external

6MHz clock if required. Note : Switching threshold of this pin is VCC/2, so if

driving from an external source, the source must be driving at 5V CMOS level or

a.c. coupled to centre around VCC/2.

28

XTOUT

OUT

Output from 6MHz Crystal Oscillator Cell. XTOUT stops oscillating during USB

suspend, so take care if using this signal to clock external logic.

31

TEST

IN

Puts device in I.C. test mode – must be tied to GND for normal operation.