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ds245b version 1.6 ? future technology devices intl. ltd. 2005 page 1 of 24 FT245BM usb fifo ( usb - parallel ) i.c. the FT245BM is the 2 nd generation of ftdis popular usb fifo i.c. this device not only adds extra functionality to its ft8u245am predecessor and reduces external component count, but also maintains a high degree of pin compatibility with the original, making it easy to upgrade or cost reduce existing designs as well as increasing the potential for using the device in new application areas. 1.0 features hardware features ? single chip usb ? parallel fifo bi-directional data transfer ? transfer data rate to 1m byte / sec - d2xx drivers ? transfer data rate to 300 kilobyte / sec - vcp drivers ? simple to interface to mcu / pld/ fpga logic with a 4 wire handshake interface ? entire usb protocol handled on-chip no usb- speci?c ?rmware programming required ? ftdis royalty-free vcp and d2xx drivers eliminate the requirement for usb driver development in most cases. ? 384 byte fifo tx buffer / 128 byte fifo rx buffer for high data throughput. ? new send immediate support via si pin for optimised data throughput. ? support for usb suspend / resume through pwren# and wakeup pins. ? support for high power usb bus powered devices through pwren# pin ? adjustable rx buffer timeout ? in-built support for event characters ? integrated level converter on fifo and control signals for interfacing to 5v and 3.3v logic ? integrated 3.3v regulator for usb io ? integrated power-on-reset circuit ? integrated 6mhz C 48mhz clock multiplier pll ? usb bulk or isochronous data transfer modes ? new bit-bang mode allows the data bus to be used as an 8 bit general purpose io port without the need for mcu or other support logic. ? 4.35v to 5.25v single supply operation ? uhci / ohci / ehci host controller compatible ? usb 1.1 and usb 2.0 compatible ? usb vid, pid , serial number and product description strings in external eeprom ? eeprom programmable on-board via usb ? compact 32ld lqfp package virtual com port (vcp) drivers for - windows 98 and windows 98 se - windows 2000 / me / xp - windows ce 4.2 - mac os-8 and os-9 - mac os-x - linux 2.40 and greater d2xx (usb direct drivers + dll s/w interface) - windows 98 and windows 98 se - windows 2000 / me / xp - windows ce 4.2 - linux 2.4 and greater application areas - easy mcu / pld / fpga interface to usb - upgrading legacy peripheral designs to usb - usb instrumentation - usb industrial control - usb audio and low bandwidth video data transfer - pda ? usb data transfer - usb mp3 player interface - usb flash card reader / writers - set top box (s.t.b.) pc - usb interface - usb digital camera interface - usb hardware modems - usb wireless modems
ds245b version 1.6 ? future technology devices intl. ltd. 2005 page 2 of 24 FT245BM usb fifo ( usb - parallel ) i.c. 2.0 enhancements this section summarises the enhancements of the 2 nd generation device compared to its ft8u245am predecessor. for further details, consult the device pin- out description and functional descriptions. ? integrated power-on-reset (por) circuit the device now incorporates an internal por function. the existing reset# pin is maintained in order to allow external logic to reset the device where required, however for many applications this pin can now be either left n/c or hard wired to vcc. in addition, a new reset output pin (rstout#) is provided in order to allow the new por circuit to provide a stable reset to external mcu and other devices. rstout# was the test pin on the previous generation of devices. ? integrated rcclk circuit in the previous devices, an external rc circuit was required to ensure that the oscillator and clock multiplier pll frequency was stable prior to enabling the clock internal to the device. this circuit is now embedded on-chip C the pin assigned to this function is now designated as the test pin and should be tied to gnd for normal operation. ? integrated level converter on fifo interface and control signals the previous devices would drive the fifo and control signals at 5v cmos logic levels. the new device has a separate vccio pin allowing the device to directly interface to 3.3v and other logic families without the need for external level converter i.c.s ? power management control for usb bus powered, high current devices 1.1 general description the FT245BM provides an easy cost-effective method of transferring data to / from a peripheral and a host p.c. at up to 8 million bits (1 megabyte) per second. its simple, fifo-like design makes it easy to interface to any microcontroller or microprocessor via io ports. to send data from the peripheral to the host computer, simply write the byte-wide data into the module when txe# is low. if the (384-byte) transmit buffer ?lls up or is busy storing the previously written byte, the device keeps txe# high in order to stop further data from being written until some of the fifo data has been transferred over usb to the host. txe# goes high after every byte written. when the host sends data to the peripheral over usb, the device will take rxf# low to let the peripheral know that at least one byte of data is available. the peripheral can read a data byte every time rxf# goes low. rxf# goes high after every byte read. by using ftdis virtual com port drivers, the peripheral looks like a standard com port to the application software. commands to set the baud rate are ignored - the device always transfers data at its fastest rate regardless of the applications baud-rate setting. alternatively, ftdis d2xx drivers allow application software to access the device directly through a published dll based api. details of the current vcp and d2xx driver can be found on ftdis web site ( http://www.ftdichip.co m )
ds245b version 1.6 ? future technology devices intl. ltd. 2005 page 3 of 24 FT245BM usb fifo ( usb - parallel ) i.c. a new pwren# signal is provided which can be used to directly drive a transistor or p-channel mosfet in applications where power switching of external circuitry is required. a new eeprom based option makes the device pull gently down its fifo interface lines when the power is shut off (pwren# is high). in this mode, any residual voltage on external circuitry is bled to gnd when power is removed thus ensuring that external circuitry controlled by pwren# resets reliably when power is restored. pwren# can also be used by external circuitry to determine when usb is in suspend mode (pwren# goes high). ? send immediate / wakeup (si / wu) signal the new send immediate / wakeup signal combines two functions on a single pin. if usb is in suspend mode (and remote wakeup is enabled in the eeprom), strobing this pin low will cause the device to request a resume from suspend (wakeup) on the usb bus. normally, this can be used to wake up the host pc. during normal operation, if this pin is strobed low any data in the device rx buffer will be sent out over usb on the next bulk-in request from the drivers regardless of the packet size. this can be used to optimise usb transfer speed for some applications. ? lower suspend current integration of rcclk within the device and internal design improvements reduce the suspend current of the FT245BM to under 100ua typical (excluding the 1.5k pull-up on usbdp) in usb suspend mode. this allows greater margin for peripherals to meet the usb suspend current limit of 500ua. ? support for usb isochronous transfers whilst usb bulk transfer is usually the best choice for data transfer, the scheduling time of the data is not guaranteed. for applications where scheduling latency takes priority over data integrity such as transferring audio and low bandwidth video data, the new device now offers an option of usb isochronous transfer via an option bit in the eeprom. ? programmable fifo tx buffer timeout in the previous device, the tx buffer timeout used to ?ush remaining data from the tx buffer was ?xed at 16ms timeout. this timeout is now programmable over usb in 1ms increments from 1ms to 255ms, thus allowing the device to be better optimised for protocols requiring faster response times from short data packets. ? relaxed vcc decoupling the 2 nd generation devices now incorporate a level of on-chip vcc decoupling. though this does not eliminate the need for external decoupling capacitors, it signi?cantly improves the ease of pcb design requirements to meet fcc, ce and other emi related speci?cations. ? bit bang mode the 2 nd generation device has a new option referred to as bit bang mode. in bit bang mode, the eight fifo data lines can be switched between fifo interface mode and an 8-bit parallel io port. data packets can be sent to the device and they will be sequentially sent to the interface at a rate controlled by an internal timer (equivalent to the prescaler of the ft232bm device). as well as allowing the device to be used stand-alone as a general purpose io controller for example controlling lights, relays and switches, some other interesting possibilities exist. for instance, it may be possible to connect the device to an sram con?gurable fpga as supplied by vendors such as altera and xilinx. the fpga device would normally be un-con?gured (i.e. have no de?ned function) at power-up. application software on the pc could use bit bang mode to download con?guration data to the fpga which would de?ne its hardware
ds245b version 1.6 ? future technology devices intl. ltd. 2005 page 4 of 24 FT245BM usb fifo ( usb - parallel ) i.c. function, then after the fpga device is con?gured the FT245BM can switch back into fifo interface mode to allow the programmed fpga device to communicate with the pc over usb. this approach allows a customer to create a generic usb peripheral whos hardware function can be de?ned under control of the application software. the fpga based hardware can be easily upgraded or totally changed simply by changing the fpga con?guration data ?le. application notes, software and development modules for this application area will be available from ftdi and other 3 rd party developers. ? less external support components as well as eliminating the rcclk rc network, and for most applications the need for an external reset circuit, we have also eliminated the requirement for a 100k pull-up on eecs to select 6mhz operation. when the FT245BM is being used without the con?guration eeprom, eecs, eesk and eedata can now be left n/c. for circuits requiring a long reset time (where the device is reset externally using a reset generator i.c., or reset is controlled by the io port of a mcu, fpga or asic device) an external transistor circuit is no longer required as the 1.5k pull-up resistor on usbdp can be wired to the rstout# pin instead of to 3.3v. note : rstout# drives out at 3.3v level, not at 5v vcc level. this is the preferred con?guration for new designs. ? extended eeprom support the previous generation of devices only supported eeprom of type 93c46 (64 x 16 bit). the new devices will also work with eeprom type 93c56 (128 x 16 bit) and 93c66 (256 x 16 bit). the extra space is not used by the device, however it is available for use by other external mcu / logic whilst the FT245BM is being held in reset. ? usb 2.0 ( full speed option ) a new eeprom based option allows the FT245BM to return a usb 2.0 device descriptor as opposed to usb 1.1. note : the device would be a usb 2.0 full speed device (12mb/s) as opposed to a usb 2.0 high speed device (480mb/s). ? multiple device support without eeprom when no eeprom (or a blank or invalid eeprom) is attached to the device, the FT245BM no longer gives a serial number as part of its usb descriptor. this allows multiple devices to be simultaneously connected to the same pc. however, we still highly recommend that eeprom is used, as without serial numbers a device can only be identi?ed by which hub port in the usb tree it is connected to which can change if the end user re-plugs the device into a different usb port. ? eereq# / eegnt# these (ft8u245am) pins are no longer supported on the FT245BM device. they have been replaced with the new si / wu and pwren# signals respectively.
ds245b version 1.6 ? future technology devices intl. ltd. 2005 page 5 of 24 FT245BM usb fifo ( usb - parallel ) i.c. 3.0 block diagram ( simpli?ed ) x8 clock multiplier serial interface engine ( sie ) usb protocol engine fifo transmit buffer 384 bytes fifo receive buffer 128 bytes 3.3 volt ldo regulator usb transceiver usb dpll 6mhz oscillator 48mhz 12mhz xtin xtout usbdp usbdm 3v3out vcc reset# test gnd fifo controller d0 d1 d2 d3 d4 d5 d6 d7 eeprom interface rd# wr eecs eesk eedata rxf# txe# pwren# reset generator rstout# 3v3out send immediate / wakeup 3.1 functional block descriptions ? 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. ? 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.
ds245b version 1.6 ? future technology devices intl. ltd. 2005 page 6 of 24 FT245BM usb fifo ( usb - parallel ) i.c. ? serial interface engine (sie) the serial interface engine (sie) block performs the parallel to serial and serial to parallel conversion of the usb data. in accordance to the usb 2.0 speci?cation, it performs bit stuf?ng / un- stuf?ng and crc5 / crc16 generation / checking on the usb data stream. ? usb protocol engine the usb protocol engine manages the data stream from the device usb control endpoint. it handles the low level usb protocol (chapter 9) requests generated by the usb host controller and the commands for controlling the functional parameters of the fifo. ? fifo receive buffer (128 bytes) data sent from the usb host to the fifo via the usb data out endpoint is stored in the fifo receive buffer and is removed from the buffer by reading the fifo contents using rd#. ? fifo transmit buffer (384 bytes) data written into the fifo using wr# is stored in the fifo transmit buffer. the host removes data from the fifo transmit data by sending a usb request for data from the device data in endpoint. ? fifo controller the fifo controller handles the transfer of data between the external fifo interface pins and the fifo transmit and receive buffers. ? reset generator the reset generator cell provides a reliable power-on reset to the device internal circuitry on power up. an additional reset# input and rstout# output are provided to allow other devices to reset the FT245BM, or the FT245BM to reset other devices respectively. during reset, rstout# is driven low, otherwise it drives out at the 3.3v provided by the onboard regulator. rstout# can be used to control the 1.5k pull-up on usbdp directly where delayed usb enumeration is required. rstout# will be low for approximately 5ms after vcc has risen above 3.5v and the device oscillator is running and reset# is high. reset# should be tied to vcc unless it is a requirement to reset the device from external logic or an external reset generator i.c. ? eeprom interface though the FT245BM will work without the optional eeprom, an external 93c46 (93c56 or 93c66) eeprom can be used to customise the usb vid, pid, serial number, product description strings and power descriptor value of the FT245BM for oem applications. other parameters controlled by the eeprom include remote wake up, isochronous transfer mode, soft pull down on power-off and usb 2.0 descriptor modes. the eeprom should be a 16 bit wide con?guration such as a microchip 93lc46b or equivalent capable of a 1mb/s clock rate at vcc = 4.35v to 5.25v. the eeprom is programmable- on board over usb using a utility available from ftdis web site ( http://www.ftdichip.co m ). this allows a blank part to be soldered onto the pcb and programmed as part of the manufacturing and test process. if no eeprom is connected (or the eeprom is blank), the FT245BM will use its built-in default vid, pid product description and power descriptor value. in this case, the device will not have a serial number as part of the usb descriptor.
ds245b version 1.6 ? future technology devices intl. ltd. 2005 page 7 of 24 FT245BM usb fifo ( usb - parallel ) i.c. 4.0 device pin-out figure 1 pin-out (lqfp-32 package ) figure 2 pin-out (schematic symbol ) eesk eedata vcc reset# rsto# 3v3out usbdp usbdm gnd pwren# si / wu rxf# txe# wr rd# vccio gnd d7 d6 d5 d4 d3 d2 d1 d0 vcc xtout xtin agnd avcc test eecs 1 8 9 16 17 24 25 32 FT245BM xxyy ftd i 25 24 23 22 21 20 19 18 15 16 14 12 11 10 6 8 7 5 27 28 4 32 1 31 2 30 3 26 13 29 17 9 3v3out usbdp usbdm rstout# xtin xtout reset# eecs eesk eedata test d0 d1 d2 d3 d4 d5 d6 d7 rd# si / wu rxf# wr txe# pwren# g n d g n d a g n d a v v c v c c v c c v c c i o
ds245b version 1.6 ? future technology devices intl. ltd. 2005 page 8 of 24 FT245BM usb fifo ( usb - parallel ) i.c. 4.1 signal descriptions table 1 - FT245BM - pinout description fifo data bus group (*** note 1) pin# signal type description 25 do i/o fifo data bus bit 0 24 d1 i/o fifo data bus bit 1 23 d2 i/o fifo data bus bit 2 22 d3 i/o fifo data bus bit 3 21 d4 i/o fifo data bus bit 4 20 d5 i/o fifo data bus bit 5 19 d6 i/o fifo data bus bit 6 18 d7 i/o fifo data bus bit 7 fifo control interface group pin# signal type description 16 rd# in enables current fifo data byte on d0..d7 when low. fetches the next fifo data byte (if available) from the receive fifo buffer when rd# goes from low to high. *** note 1 15 wr in writes the data byte on the d0..d7 into the transmit fifo buffer when wr goes from high to low. *** note 1 14 txe# out when high, do not write data into the fifo. when low, data can be written into the fifo by strobing wr high then low. *** note 2 12 rxf# out when high, do not read data from the fifo. when low, there is data available in the fifo which can be read by strobing rd# low then high again *** note 2 usb interface group pin# signal type description 7 usbdp i/o usb data signal plus (requires 1.5k pull-up to 3v3out or rstout#) 8 usbdm i/o usb data signal minus eeprom interface group pin# signal type description 32 eecs i/o eeprom C chip select. for 48mhz operation pull eecs to gnd using a 10k resistor. for 6mhz operation no resistor is required. *** note 3 1 eesk out clock signal to eeprom. adding a 10k pull down resistor onto eesk will cause the FT245BM to use usb product id 6005 (hex) instead of 6001 (hex). all of the other usb device descriptors are unchanged. *** note 3 2 eedata i/o eeprom C data i/o connect directly to data-in of the eeprom and to data- out of the eeprom via a 2.2k resistor. also pull data-out of the eeprom to vcc via a 10k resistor for correct operation. *** note 3
ds245b version 1.6 ? future technology devices intl. ltd. 2005 page 9 of 24 FT245BM usb fifo ( usb - parallel ) i.c. power control group pin# signal type description 10 pwren# out goes low after the device is con?gured 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 FT245BM. 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 C must be tied to gnd for normal operation.
ds245b version 1.6 ? future technology devices intl. ltd. 2005 page 10 of 24 FT245BM usb fifo ( usb - parallel ) i.c. power and gnd group pin# signal type description 6 3v3out out 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. 3,26 vcc pwr +4.35 volt to +5.25 volt vcc to the device core, ldo and none-fifo interface pins. 13 vccio pwr +3.0 volt to +5.25 volt vcc to the fifo 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. 9,17 gnd pwr device - ground supply pins 30 avcc pwr device - analog power supply for the internal x8 clock multiplier 29 agnd pwr device - analog ground supply for the internal x8 clock multiplier note 1 : in input mode, these pins are pulled to vccio via internal 200k resistors. these can be programmed to gently pull low during usb suspend ( pwren# = 1 ) by setting this option in the eeprom. note 2: during device reset, these pins are tri-state but pulled up to vccio via internal 200k resistors. note 3: during device reset, these pins are tri-state but pulled up to vcc via internal 200k resistors.
ds245b version 1.6 ? future technology devices intl. ltd. 2005 page 11 of 24 FT245BM usb fifo ( usb - parallel ) i.c. FT245BM timing diagram C fifo read cycle time description min max unit t1 rd active pulse width 50 ns t2 rd to rd pre-charge time 50 + t6 ns t3 rd active to valid data *** note 4 20 50 ns t4 valid data hold time from rd inactive *** note 4 0 ns t5 rd inactive to rxf# 0 25 ns t6 rxf inactive after rd cycle 80 ns *** note 4 - load 30 pf FT245BM timing diagram C fifo write cycle time description min max unit t7 wr active pulse width 50 ns t8 wr to wr pre-charge time 50 ns t9 data setup time before wr inactive 20 ns t10 data hold time from wr inactive 0 ns t11 wr inactive to txe# 5 25 ns t12 txe inactive after wr cycle 80 ns valid data txe# t7 t8 t12 t9 t10 t11 wr d0..d7 d0..d7 rd# rxf# valid data t1 t2 t6 t3 t4 t5
ds245b version 1.6 ? future technology devices intl. ltd. 2005 page 12 of 24 FT245BM usb fifo ( usb - parallel ) i.c. figure 3 C 32 ld lqfp package dimensions 5.0 package outline the FT245BM is supplied in a 32 pin lqfp package as standard. this package has a 7mm x 7mm body ( 9mm x 9mm including leads ) with leads on a 0.8mm pitch. the above drawing shows the lqfp-32 package C all dimensions are in millimetres. note that there are two date code formats used - xxyy = date code where xx = 1 or 2 digit year number, yy = 2 digit week number); or xyy-1 where x = 1 digit year number, yy = 2 digit week number. a lead free version of the lqfp-32 is available, part number ft245bl an alternative 5mm x 5mm leadless qfn is also available for projects where package area is critical. part number for this version is ft245bq. the ft245bq is also a lead free package. see the seperate datasheet for package dimensions. pin # 1 0.25 1.60 max 12 o +/- 1 o 1.4 +/- 0.05 0.2 min 1 0.05 min 0.37 +/- 0.07 0.35 +/- 0.05 0.09 min 0.2 max 0.09 min 0.16 max 7 9 7 9 32 0.8 FT245BM ftdi xxyy
ds245b version 1.6 ? future technology devices intl. ltd. 2005 page 13 of 24 FT245BM usb fifo ( usb - parallel ) i.c. 6.0 absolute maximum ratings these are the absolute maximum ratings for the FT245BM device i n accordance with the absolute maximum rating system (iec 60134). exceeding these may cause permanent damage to the device. parameter value units storage temperature C65 o c to + 150 o c degrees c floor life (out of bag) at factory ambient (30 o c/60% relative humidity) 192 hours (level 3 compliant) **note 5 ambient temperature (power applied) 0 o c to + 70 o c degrees c m.t.b.f. (at 35 o c) 247484 hours 28 years vcc supply voltage -0.5 to +6.00 v dc input voltage - inputs -0.5 to +(vcc + 0.5) v dc input voltage - high impedance bidirectionals -0.5 to +(vcc + 0.5) v dc output current C outputs 24 ma dc output current C low impedance bidirectionals 24 ma power dissipation (vcc = 5.25v) 500 mw electrostatic discharge voltage (human body model) (i < 1ua) +/- 3000 v latch up current (vi = +/- 10v maximum, for 10 ms) +/-200 ma *** note 5 - if devices are stored out of the packaging beyond this time limit the devices should be baked before use. the devices should be ramped up to a temperature of 110 o c and baked for 8 to 10 hours. 6.1 d.c. characteristics dc characteristics ( ambient temperature = 0 to 70 o c ) operating voltage and current parameter description min typ max units conditions vcc1 vcc operating supply voltage 4.35 5.0 5.25 v vcc2 vccio operating supply voltage 3.0 - 5.25 v icc1 operating supply current - 25 - ma normal operation icc2 operating supply current - 100 200 ua usb suspend *** note 6 ***note 6 C supply current excludes the 200ua nominal drawn by the external pull-up resistor on usbdp. fifo data / control bus io pin characteristics ( vccio = 5.0v ) parameter description min typ max units conditions voh output voltage high 3.2 4.1 4.9 v i source = 2ma vol output voltage low 0.3 0.4 0.6 v i sink = 2 ma vin input switching threshold 1.3 1.6 1.9 v *** note 7 vhys input switching hysteresis 50 55 60 mv
ds245b version 1.6 ? future technology devices intl. ltd. 2005 page 14 of 24 FT245BM usb fifo ( usb - parallel ) i.c. fifo data / control bus io pin characteristics ( vccio = 3v to 3.6v ) parameter description min typ max units conditions voh output voltage high 2.2 2.7 3.2 v i source = 2ma vol output voltage low 0.3 0.4 0.5 v i sink = 4 ma vin input switching threshold 1.0 1.2 1.5 v *** note 7 vhys input switching hysteresis 20 25 30 mv ***note 7 C inputs or io pins in input mode have an internal 200k pull-up resistor to vccio. xtin / xtout pin characteristics parameter description min typ max units conditions voh output voltage high 4.0 - 5.0 v fosc = 6mhz vol output voltage low 0.1 - 1.0 v fosc = 6mhz vin input switching threshold 1.8 2.5 3.2 v reset#, test, eecs, eesk, eedata, io pin characteristics parameter description min typ max units conditions voh output voltage high 3.2 4.1 4.9 v i source = 2ma vol output voltage low 0.3 0.4 0.6 v i sink = 2 ma vin input switching threshold 1.3 1.6 1.9 v *** note 8 vhys input switching hysteresis 50 55 60 mv ***note 8 C eecs, eesk and eedata pins have an internal 200k pull-up resistor to vcc rstout pin characteristics parameter description min typ max units conditions voh output voltage high 3.0 - 3.6 v i source = 2ma vol output voltage low 0.3 - 0.6 v i sink = 2 ma usb io pin characteristics parameter description min typ max units conditions uvoh io pins static output ( high) 2.8 3.6 v ri = 1.5k to 3v3out ( d+ ) ri = 15k to gnd ( d- ) uvol io pins static output ( low ) 0 0.3 v ri = 1.5k to 3v3out ( d+ ) ri = 15k to gnd ( d- ) uvse single ended rx threshold 0.8 2.0 v ucom differential common mode 0.8 2.5 v uvdif differential input sensitivity 0.2 v udrvz driver output impedance 29 44 ohm *** note 9
ds245b version 1.6 ? future technology devices intl. ltd. 2005 page 15 of 24 FT245BM usb fifo ( usb - parallel ) i.c. 7.0 device con?guration examples 7.1 oscillator con?gurations figure 4 3 pin ceramic resonator con?guration figure 5 crystal or 2-pin ceramic resonator con?guration figure 4 illustrates how to use the FT245BM with a 3-pin ceramic resonator . a suitable part would be a ceramic resonator from muratas ceralock range. (murata part number cstcr6m00g15), or equivalent. 3-pin ceramic resonators have the load capacitors built into the resonator so no external loading capacitors are required. this makes for an economical con?guration. the accuracy of this murata ceramic resonator is +/- 0.1% and it is speci?cally designed for usb full speed applications. a 1 mohm loading resistor across xtin and xtout is recommended in order to guarantee this level of accuracy. other ceramic resonators with a lesser degree of accuracy ( typically +/- 0.5% ) are technically outwith the usb speci?cation, but it has been calculated that using such a device will work satisfactorily in practice with a FT245BM design. figure 5 illustrates how to use the FT245BM with a 6mhz crystal or 2-pin ceramic resonator . in this case, these devices do not have in-built loading capacitors so these have to be added between xtin, xt out and gnd as shown. a value of 27pf is shown as the capacitor in the example C this will be good for many crystals and some resonators but do select the value based on the manufacturers recommendations wherever possible. if using a crystal, use a parallel cut type. if using a resonator, see the previous note on frequency accuracy. xtin xtout 27 28 FT245BM 3-pin resonator 6mhz 1m xtin xtout 27 28 FT245BM 2 - pin resonator or crystal 6mhz 27pf 27pf
ds245b version 1.6 ? future technology devices intl. ltd. 2005 page 16 of 24 FT245BM usb fifo ( usb - parallel ) i.c. 7.2 eeprom con?guration figure 6 eeprom con?guration figure 6 illustrates how to connect the FT245BM to the 93c46 (93c56 or 93c66) eeprom. eecs (pin 32) is directly connected to the chip select (cs) pin of the eeprom. eesk (pin 1) is directly connected to the clock (sk) pin of the eeprom. eedata (pin 2) is directly connected to the data in (din) pin of the eeprom. there is a potential condition whereby both the data output (dout) of the eeprom can drive out at the same time as the eedata pin of the FT245BM. to prevent potential data clash in this situation, the dout of the eeprom is connected to eedata of the FT245BM via a 2.2 k resistor. following a power-on reset or a usb reset, the FT245BM will scan the eeprom to ?nd out a) if an eeprom is attached to the device and b) if the data in the device is valid. if both of these are the case, then the FT245BM will use the data in the eeprom, otherwise it will use its built-in default values. when a valid command is issued to the eeprom from the FT245BM, the eeprom will acknowledge the command by pulling its dout pin low. in order to check for this condition, it is necessary to pull dout high using a 10k resistor. if the command acknowledge doesnt happen then eedata will be pulled high by the 10k resistor during this part of the cycle and the device will detect an invalid command or no eeprom present. there are two varieties of these eeproms on the market C one is con?gured as being 16 bits wide, the other is con?gured as being 8 bits wide. these are available from many sources such as microchip, st micro, issi etc. the FT245BM requires eeproms with a 16-bit wide con?guration such as the microchip 93lc46b device. the eeprom must be capable of reading data at a 1mb clock rate at a supply voltage of 4.35v to 5.25v . most available parts are capable of this. check the manufacturers data sheet to ?nd out how to connect pins 6 and 7 of the eeprom. some devices specify these as no-connect, others use them for selecting 8 / 16 bit mode or for test functions. some other parts have their pinout rotated by 90 o so please select the required part and its options carefully. it is possible to share the eeprom between the FT245BM and another external device such as an mcu. however , this can only be done when the FT245BM is in its reset condition as it tri-states its eeprom interface at that time. a typical con?guration would use four bits of an mcu io port. one bit would be used to hold the FT245BM reset (using reset#) on power-up, the other three would connect to the eecs, eesk and eeda ta pins of the FT245BM in order to read / write data to the eeprom at this time. once the mcu has read / written the eeprom, it would take reset# high to allow the FT245BM to con?gure itself and enumerate over usb. eecs eedata 32 FT245BM eesk 1 2 2 cs sk din dout gnd nc nc vcc eeprom - 93c46 / 56 / 66 1 3 4 5 6 7 8 vcc 10k 2k2 vcc
ds245b version 1.6 ? future technology devices intl. ltd. 2005 page 17 of 24 FT245BM usb fifo ( usb - parallel ) i.c. vcc 27r usb "b" connector 27r usb dm rstout# 8 FT245BM usb dp 7 5 v c c v c c v c c i o 3 26 13 1 2 3 4 ferrite bead 1k5 33nf 3v3out 6 470r a v c c 30 0.1uf g n d g n d a g n d 9 17 29 10nf vcc reset# 4 decoupling capacitors 10uf vcc 0.1uf 0.1uf + 7.3 usb bus powered and self powered con?guration figure 7 usb bus powered con?guration figure 7 illustrates a typical usb bus powered con?guration. a usb bus powered device gets its power from the usb bus. basic rules for usb bus power devices are as follows C a) on plug-in, the device must draw no more than 100ma b) on usb suspend the device must draw no more than 500ua. c) a bus powered high power device (one that draws more than 100ma) should use the pwren# pin to keep the current below 100ma on plug-in and 500ua on usb suspend. d) a device that consumes more than 100ma can not be plugged into a usb bus powered hub e) no device can draw more that 500ma from the usb bus. the power descriptor in the eeprom should be programmed to match the current draw of the device. a ferrite bead is connected in series with usb power to prevent noise from the device and associated circuitry (emi) being radiated down the usb cable to the host. the value of the ferrite bead depends on the total current required by the circuit C a suitable range of ferrite beads is available from steward ( www.steward.co m ) for example steward part # mi0805k400r-00 also available as digikey part # 240-1035-1.
ds245b version 1.6 ? future technology devices intl. ltd. 2005 page 18 of 24 FT245BM usb fifo ( usb - parallel ) i.c. figure 8 usb self powered con?guration figure 8 illustrates a typical usb self powered con?guration. a usb self powered device gets its power from its own power supply and does not draw current from the usb bus. the basic rules for usb self power devices are as follows C a) a self-powered device should not force current down the usb bus when the usb host or hub controller is powered down. b) a self powered device can take as much current as it likes during normal operation and usb suspend as it has its own power supply. c) a self powered device can be used with any usb host and both bus and self powered usb hubs the usb power descriptor option in the eeprom should be programmed to a value of zero (self powered). to meet requirement a) the 1.5k pull-up resistor on usbdp is connected to rstout# as per the bus-power circuit. however, the usb bus power is used to control the reset# pin of the FT245BM device. when the usb host or hub is powered up rstout# will pull the 1.5k resistor on usb dp to 3.3v, thus identifying the device as a full speed device to usb. when the usb host or hub power is off, reset# will go low and the device will be held in reset. as reset# is low, rstout# will also be low, so no current will be forced down usbdp via the 1.5k pull-up resistor when the host or hub is powered down. failure to do this may cause some usb host or hub controllers to power up erratically. note : when the FT245BM is in reset, the fifo interface pins all go tri-state. these pins have internal 200k pull-up resistors to vccio so they will gently pull high unless driven by some external logic. vcc 27r usb "b" connector 27r usb dm rstout# 8 FT245BM usb dp 7 5 v c c v c c v c c i o 3 26 13 1 2 3 4 1k5 33nf 3v3out 6 470r a v c c 30 0.1uf g n d g n d a g n d 9 17 29 reset# 4 10k 4k7 decoupling capacitors 10uf vcc 0.1uf 0.1uf +
ds245b version 1.6 ? future technology devices intl. ltd. 2005 page 19 of 24 FT245BM usb fifo ( usb - parallel ) i.c. figure 9 bus powered circuit with 3.3v logic drive / supply voltage ferrite bead 470r 0.1uf vcc 27r usb "b" connector 27r usb dm 8 FT245BM usb dp 7 v c c v c c v c c i o 3 26 13 1 2 3 4 33nf 3v3out 6 a v c c 30 10nf 0.1uf in out gnd 3.3v ldo regulator 3.3v power to external logic figure 9 shows how to con?gure the FT245BM to interface with a 3.3v logic device. in this example, a discrete 3.3v regulator is used to supply the 3.3v logic from the usb supply . vccio is connected to the output of the 3.3v regulator, which in turn will cause the fifo interface io pins to drive out at 3.3v level. for usb bus powered circuits some considerations have to be taken into account when selecting the regulator C a) the regulator must be capable of sustaining its output voltage with an input voltage of 4.35 volts. a low drop out (ldo) regulator must be selected. b) the quiescent current of the regulator must be low in order to meet the usb suspend total current requirement of <= 500ua during usb suspend. an example of a regulator family that meets these requirements is the microchip (t elcom) tc55 series. these devices can supply up to 250ma current and have a quiescent current of under 1ua. in some cases, where only a small amount of current is required (< 5ma) , it may be possible to use the in-built regulator of the FT245BM to supply the 3.3v without any other components being required. in this case, connect vccio to the 3v3out pin of the FT245BM. note : it should be emphasised that the 3.3v supply for vccio in a bus powered design with a 3.3v logic interface should come from an ldo which is supplied by usb bus, or from the 3v3out pin of the FT245BM, and not from any other source.
ds245b version 1.6 ? future technology devices intl. ltd. 2005 page 20 of 24 FT245BM usb fifo ( usb - parallel ) i.c. figure 10 self powered circuit with 3.3 v logic drive / supply voltage figure 10 is an example of a usb self powered design with 3.3v interface. in this case vccio is supplied by an external 3.3v supply in order to make the device io pins drive out at 3.3v logic level, thus allowing it to be connected to a 3.3v mcu or other external logic. a usb self powered design uses its own power supplies, and does not draw any of its power from the usb bus. in such cases, no special care need be taken to meet the usb suspend current (0.5 ma) as the device does not get its power from the usb port. as with bus powered 3.3v interface designs, in some cases, where only a small amount of current is required (<5ma), it may be possible to use the in-built regulator of the FT245BM to supply the 3.3v without any other components being required. in this case, connect vccio to the 3v3out pin of the FT245BM. note that if si/wu is not being used it should be pulled up to vccio. vcc5v 27r usb "b" connector 27r usb dm rstout# 8 FT245BM usb dp 7 5 v c c i o 13 1 2 3 4 1k5 33nf 3v3out 6 0.1uf g n d g n d a g n d 9 17 29 reset# 4 10k 4k7 decoupling capacitors 10uf vcc5v 0.1uf 0.1uf + vcc3v vcc3v si/wu v c c v c c 3 26 470r a v c c 30 11
ds245b version 1.6 ? future technology devices intl. ltd. 2005 page 21 of 24 FT245BM usb fifo ( usb - parallel ) i.c. figure 11 bus powered circuit with power control usb bus powered circuits need to be able to power down in usb suspend mode in order to meet the <= 500ua total suspend current requirement (including external logic). some external logic can power itself down into a low current state by monitoring the pwren# pin. for external logic that cannot power itself down in that way , the FT245BM provides a simple but effective way of turning off power to external circuitry during usb suspend. figure 11 shows how to use a discrete p-channel logic level mosfet to control the power to external logic circuits. a suitable device could be a fairchild ndt456p, or international recti?er irlml6402, or equivalent. it is recommended that a soft start circuit consisting of a 1k series resistor and a 0.1 uf capacitor are used to limit the current surge when the mosfet turns on. without the soft start circuit there is a danger that the transient power surge of the mosfet turning on will reset the FT245BM, or the usb host / hub controller. the values used here allow attached circuitry to power up with a slew rate of ~12.5 v per millisecond, in other words the output voltage will transition from gnd to 5 v in approximately 400 microseconds. alternatively, a dedicated power switch i.c. with inbuilt soft-start can be used instead of a mosfet. a suitable power switch i.c. for such an application would be a micrel ( www.micrel.co m ) mic2025-2bm or equivalent. please note the following points in connection with power controlled designs C a) the logic to be controlled must have its own reset circuitry so that it will automatically reset itself when power is re- applied on coming out of suspend. b) set the pull-down on suspend option in the FT245BMs eeprom. c) for usb high-power bus powered device (one that consumes greater than 100 ma, and up to 500 ma of current from the usb bus), the power consumption of the device should be set in the max power ? eld in the eeprom. a high-power bus powered device must use this descriptor in the eeprom to inform the system of its power requirements. d) for 3.3v power controlled circuits vccio must not be powered down with the external circuitry (pwren# gets its vcc supply from vccio). either connect the power switch between the output of the 3.3v regulator and the external 3.3v logic or if appropriate power vccio from the 3v3out pin of the FT245BM. ferrite bead 470r 0.1uf vcc 27r usb "b" connector 27r usb dm 8 FT245BM usb dp 7 v c c v c c v c c i o 3 26 13 1 2 3 4 33nf 3v3out 6 a v c c 30 10nf pwren# 15 0.1uf switched 5v power to external logic p-channel power mosfet s g d 0.1uf 1k soft start circuit
ds245b version 1.6 ? future technology devices intl. ltd. 2005 page 22 of 24 FT245BM usb fifo ( usb - parallel ) i.c. figure 12 microprocessor interface example 25 24 23 22 21 20 19 18 15 16 14 12 11 d0 d1 d2 d3 d4 d5 d6 d7 rd# si / wu rxf# wr txe# FT245BM io10 io11 io12 io13 io14 io15 io16 io17 io20 io24 io23 io21 io22 microcontroller io port 1 io port 2 ( optional ) figure 12 illustrates a typical interface between the FT245BM and a microcontroller (mcu). this examples uses two io ports of the mcu, one port (8 bits) to transfer data and the other port (4 / 5 bits) to monitor the txe# and rxf# status bits and generate the rd# and wr strobes to the FT245BM as required. optionally , si / wu can be connected to another io pin if this function is required. if the si / wu function is not required, tie this pin of the FT245BM to vccio. if the mcu is handling power management functions, then pwren# should also be connected to an io pin of the mcu. the 8 data bits of port 1 can be shared with other peripherals when the mcu is not accessing the FT245BM.
ds245b version 1.6 ? future technology devices intl. ltd. 2005 page 23 of 24 FT245BM usb fifo ( usb - parallel ) i.c. 8.0 document revision history ds245b version 1.0 C initial document created 8th august 2002. ds245b version 1.1 C updated 23 october 2003 ? pin and package naming made consistent throughout data sheet. ? section 1.0 corrected data transfer rate for vcp drivers. ? section 1.0 amended to re?ect availability of mac os x drivers. ? section 1.1 description of behaviour of txe# and rxf# amended. ? section 3.1 minor changes to functional block descriptions. ? section 2.0 compatible eeprom con?gurations corrected. ? section 4.1 si/wu pin description amended. ? section 4.1 rstout# pin description amended. ? section 4.1 eeprom interface pin descriptions amended. ? section 4.1 note 2 should have referred to vccio, not vcc. ? section 4.1 fifo timing diagram amended. ? section 6.1 minimum operating supply voltage adjusted. ? section 7.1 updated recommended ceramic resonator part number and circuit con? guration. ? section 7.3 usb self powered con?guration (1) (original figure 8) removed. recommended circuit for usb self powered designs updated. ? section 7.3 self powered circuit with 3.3v logic drive / supply voltage added (new ? gure 8). ? section 7.3 figure 11 bus powered circuit with power control updated to add soft start circuit on mosfet. circuit description amended. ds245b version 1.2 C updated 20 november 2003. ? section 6.1 fifo data control bus io pin characteristics amended ? section 6.1 reset#, test, eecs, eesk, and eedata pin characteristics amended. ? section 6.1 rstout# pin characteristics amended. ds245b version 1.3 C updated 10 december 2003 ? section 5.0 package drawing amended. ? section 6.0 floor life / relative humidity speci?cation added. esd and latch up speci?cations amended. ? section 7.1 required accuracy of crystal / resonator corrected. ds245b version 1.4 C updated 10 february 2004 ? grammar corrections. ? section 10.0 ftdi address updated ? section 4.1 vccio pin description ammended. ds245b version 1.5 C updated march 2004 ? section 4.1 fifo eesk pin description amended. ? section 4.1 fifo wr timings and diagram amended. ? section 7.3 figure 10 si/wu pin number corrected ? section 7.3 figure 11 pwren# pin number corrected ds245b version 1.6 C updated february 2005 ? section 1 - win ce vcp drivers now available ? section 1 - d2xx drivers for win ce and linux now available ? section 5 ft245bl (lead free) and ft245bq (lead free qfn package) now available
ds245b version 1.6 ? future technology devices intl. ltd. 2005 page 24 of 24 FT245BM usb fifo ( usb - parallel ) i.c. agents and sales representatives at the time of writing our sales network covers over 40 different countries world-wide. please visit the sales network page of our web site for the contact details our distributor(s) in your country. see : http://www.ftdichip.com/ftdisti.ht m future technology devices intl. limited 373 scotland street glasgow g5 8qb, united kingdom. tel : +44 ( 0 )141 429 2777 fax : +44 ( 0 )141 429 2758 e-mail ( sales ) : sales1@ftdichip.co m e-mail ( support ) : support1@ftdichip.co m e-mail ( general enquiries ) : admin1@ftdichip.co m web site url : http://www.ftdichip.co m 9.0 disclaimer ? future technology devices international limited , 2002 - 2004 neither the whole nor any part of the information contained in, or the product described in this manual, may be adapted or reproduced in any material or electronic form without the prior written consent of the copyright holder . this product and its documentation are supplied on an as-is basis and no warranty as to their suitability for any particular purpose is either made or implied. future technology devices international ltd. will not accept any claim for damages howsoever arising as a result of use or failure of this product. your statutory rights are not affected. this product or any variant of it is not intended for use in any medical appliance, device or system in which the failure of the product might reasonably be expected to result in personal injury . this document provides preliminary information that may be subject to change without notice. 10.0 contact information

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