FT232BM USB UART ( USB - Serial) I.C.
POWER CONTROL GROUP
Pin#
10
15
Signal
SLEEP#
PWREN#
Type
OUT
OUT
Description
Goes Low during USB Suspend Mode. Typically used to power-down an external
TTL to RS232 level converter i.c. in USB <=> RS232 converter designs.
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.
Bus Powered – Tie Low / Self Powered – Tie High (to VCCIO)
14
PWRCTL
IN
MISCELLANEOUS SIGNAL GROUP
Pin#
4
5
Signal
RESET#
RSTOUT#
Type
IN
OUT
Description
Can be used by an external device to reset the FT232BM. If not required, tie to
VCC.
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.
LED Drive - Pulses Low when Transmitting Data via USB
LED Drive - Pulses Low when Receiving Data via USB
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.
Output from 6MHz Crystal Oscillator Cell. XTOUT stops oscillating during USB
suspend, so take care if using this signal to clock external logic.
Puts device in I.C. test mode – must be tied to GND for normal operation.
12
11
27
TXLED#
RXLED#
XTIN
O.C.
O.C.
IN
28
31
XTOUT
TEST
OUT
IN
POWER AND GND GROUP
Pin#
6
Signal
3V3OUT
Type
OUT
Description
3.3 volt Output from the integrated L.D.O. regulator This pin should be decoupled
to GND using a 33nF ceramic capacitor in close proximity to the device pin. Its
prime purpose is to provide the internal 3.3V supply to the USB transceiver cell
and the RSTOUT# pin. A small amount of current (<= 5mA) can be drawn from
this pin to power external 3.3v logic if required.
+4.35 volt to +5.25 volt VCC to the device core, LDO and non-UART interface
pins.
+3.0 volt to +5.25 volt VCC to the UART interface pins 10..12, 14..16 and 18..25.
When interfacing with 3.3V external logic in a bus powered design connect
VCCIO to a 3.3V supply generated from the USB bus. When interfacing with
3.3V external logic in a self powered design connect VCCIO to the 3.3V supply
of the external logic. Otherwise connect to VCC to drive out at 5V CMOS level.
Device - Ground Supply Pins
Device - Analog Power Supply for the internal x8 clock multiplier
Device - Analog Ground Supply for the internal x8 clock multiplier
3,26
13
VCC
VCCIO
PWR
PWR
9,17
30
29
GND
AVCC
AGND
PWR
PWR
PWR
**Note 1 -
During device reset, these pins are tri-state but pulled up to VCC via internal 200K resistors.
DS232B Version 1.8
© Future Technology Devices Intl. Ltd. 2005
Page 9 of 25
FTDI [ FUTURE TECHNOLOGY DEVICES INTERNATIONAL LTD. ]
