ACS102A

ACS102A SEMTECH | Alldatasheet

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Advanced Communications ACS102A Data Sheet Transmitter and Receiver Functions This device offers one high speed and three low speed full duplex channels to the user in a completely transparent way, appearing as 4 full duplex channels even though the medium connecting the devices may only be a single fiber link. Data from the TxD and low frequency channels is time compressed in an internal FIFO and sent over the fiber link in a burst within a predefined window. The device at each end of the link automatically synchronise with each other such that the transmit and receive windows are interleaved. The TxD input data of the transmitting modem is also data compressed. The 3B4B encoding method is used for communication between ACS102As, thus ensuring that there is no DC component in the signal. The encoding and decoding is transparent to the user. In the receiving modem, 3B4B encoding ensures easy extraction of the bit-clock. The received data is filtered, decoded, and then stored in the output memory. The memory provides time expansion, de-jittering and frequency compensation functions. The data is then decompressed and directed to the RxD output pin, appearing after a minimal delay, in the same format as that presented at the TxD pin at the far end. Operational Modes The ACS102A is compatible with the ACS102 but offers over twice the max data rate and incorporates the laser interface modes previously associate with the ACS402. The ACS102A is a pin and functional compatible replacement for both the ACS102 and ACS402. The following sections detail the operating modes for all configurations of LED, LASER and LED/PIN or LASER/PIN combinations. Additional modes are also described for new ways of interfacing the device with external PIN / amplifier modules. LED Interface Modes Mode 1 - Single Fiber LED mode Setup : DP5=0, DP4=0, DP3=0, DP2=1, DP1=0 This is the operational mode for single fiber transmission with a PPLED. The LED is used for both transmission and reception of data over the fiber. An example circuit diagram showing the necessary connections is shown in figure 4. This also shows an example circuit for interfacing to the RS232 voltage levels of a PC serial port. Mode 2 - Dual Fiber LED/PIN mode Setup : DP5=0, DP4=0, DP3=0, DP2=1, DP1=1 This is a twin-fiber mode where the LED is used for transmission and a separate PIN Diode is used for reception. This allows the use of less expensive standard LEDs and PINs rather than bi-directional PPLEDs or Duplex devices. An example circuit diagram showing the necessary connections is shown in figure 5. LASER Interface Modes Mode 3 - Dual Fiber LASER/PIN mode Setup : DP5=0, DP4=1, DP3=0, DP2=1, DP1=0 This is a twin-fiber mode where the LASER is used for transmission and a separate PIN Diode is used for reception. An example circuit diagram showing the necessary connections is shown in figure 6. Differential reception from the PIN diode is used to maximise sensitivity. Since PINP is also used for LASER current control via monitoring of the monitor diode current, the LAP and LAN pins are automatically floated during data reception. Either 3 or 4 pin LASERs may be used in this mode. For 4 pin LASERS the extra pin of the monitor diode cathode is connected to the LASER anode, the same as it is shown in figure 6 with the internal connection of a typical 3-pin LASER. Single/Dual Fiber Modem for Asynchronous Data Rates from DC to 160kbps LASER FiberLAP PINP LAN 3-pin LASER single fiber mode LASER FiberLAP PINP LAN 4-pin LASER single fiber mode PINN Mode 4 - Single Fiber 3-pin LASER/PIN mode Setup : DP5=0, DP4=0, DP3=1, DP2=0, DP1=1 This is a single-fiber mode where the LASER is used for transmis- sion and the monitor PIN diode within the LASER is used for reception. Differential reception from the PIN diode is used to maximise sensitivity. Connections are shown below : Mode 5 - Single Fiber 4-pin LASER/PIN mode Setup : DP5=0, DP4=0, DP3=1, DP2=0, DP1=0 This is a single-fiber mode where the LASER is used for transmis- sion and the monitor PIN diode within the LASER is used for reception. Differential reception from the PIN diode is used to maximise sensitivity. Connections are shown below : LASER Duplex Device Use The Laser duplex device is composed of a 3 or 4 pin Laser for transmission and a PIN diode for reception in a single housing. Mode 3, as detailed previously is used for interfacing to these devices. The Duplex devices are driven by the ACS102A in a half- duplex manner, even though to the user it appears as a full duplex link. As a consequence potential cross-talk between the transmit- ter and receiver is ignored, allowing excellent performance from low cost components. Additional Alternative Modes The previous modes detail the most common setups for most typical LED, LED/PIN or LASER/PIN combinations. Many other possible operating modes are possible via the DP1-5 pins setups. Some of the other less common connection combinations are shown below. These include modes for using a LASER as a receiver as well as a transmitter in a single fiber link, where the LASER device supports this, receiving from both the LASER and monitor PIN, and modes for digital interfacing to external PIN/ transimpedance amplifier (TIA) modules. Only use those setups on DP1-5 indicated in this specification, other pin combinations may activate unpublicised functional or test modes which may lead to damage of the LASER, where this is used. Mode 6 - Single Fiber 4-pin LASER/PIN mode (Las & mon recv) Setup : DP5=0, DP4=0, DP3=0, DP2=0, DP1=0 This is a single-fiber mode where the LASER is used for transmis- sion and the LASER and the monitor PIN diode within the LASER is used for reception. Connections are as in mode 5.

Advanced Communications ACS102A Data Sheet Mode 7 - Single Fiber 3-pin LASER/PIN mode (Laser recv) Setup : DP5=0, DP4=0, DP3=0, DP2=0, DP1=0 This is a single-fiber mode where the LASER is used for transmis- sion and only the LASER is used for reception. Connections are as in mode 4. Preamp Interface modes Mode 8 - Preamp Voltage Input & LED Drive Setup : DP5=1, DP4=0, DP3=1, DP2=0, DP1=0, NSB=0 This is a mode for use with external amplifier and PIN modules. An LED is used for transmission and connected as normal with its anode to LAP and cathode to LAN. The differential voltage from an external PIN/TIA module is connected to PINN and PINP via 100pF capacitors to provide DC isolation. The signals should be connected such that PINP is connected to the TIA output that goes high when light is received. A single input can also be applied from a single ended PIN/TIA by feeding the input to PINP only, PINN is left floating. This mode uses the new NSB pin, in all other modes this pin should be left disconnected or connected to VA+. Mode 9 - Preamp Voltage Input & LASER Drive Setup : DP5=1, DP4=0, DP3=1, DP2=0, DP1=1, NSB=0 This is a mode for use with external amplifier and PIN modules. A LASER is used for transmission and connected as normal as described under mode 3. The differential voltage from an external PIN/TIA module is connected to PINN and PINP via 100pF capacitors to provide DC isolation. The signals should be connected such that PINP is connected to the TIA output that goes high when light is received. A single input can also be applied from a single ended PIN/TIA by feeding the input to PINP only. With a LASER drive the PINN and PINP inputs are also connected to the LASER monitor diode. This may induce extra noise but should not interfere with the operation. This mode uses the new NSB pin, in all other modes this pin should be left disconnected or connected to VA+. Digital interface modes Mode 10 - Digital Data Input & LASER Drive Setup : DP5=0, DP4=1, DP3=1, DP2=0, DP1=0 This is a mode for use with external amplifier and PIN modules that provide fully digital output levels. A LASER is used for transmission and connected as normal as described under mode 3. The output from an external PIN/TIA module is connected to CNT. The polarity of the input should be such that CNT that goes high when light is received. Mode 11 - Digital Data Input & LED Drive Setup : DP5=1, DP4=1, DP3=0, DP2=1, DP1=0 This is a mode for use with external amplifier and PIN modules that provide fully digital output levels. An LED is used for transmission and connected as normal as shown in figure 5. The output from an external PIN/TIA module is connected to CNT. The polarity of the input should be such that CNT that goes high when light is received. Transmit Current Control LED current control The LED transmit current is not critical though it is important not to exceed the LED manufacturer's recommendation for maximum current. The current is controlled by a resistance Rtrc connected between TRC and GND. The lower the value of Rtrc the greater the current. The lower limit for Rtrc is 800Ω while a practical maximum is 40kΩ . The LED current is inversely proportional to Rtrc while Rtrc > 800Ω . LED current = (100 / Rtrc) +/- 25 % LASER current control The LASER output current must be set for each individual device in accordance with the manufacturer’s recommendations. The output current to the LASER is controlled by a variable resistor (Rtrc) between TRC and ground. The lower the value of Rtrc the greater the current. The minimum value of Rtrc is 800Ω. The ACS102A derives and controls the average optical power being produced by measuring the current in the LASER's monitor PIN diode and integrating this measurement using the capacitor on the CTX pin, which is typically 10nF. A control loop is established which works to maintain the average optical power at a constant level whilst parameters such as voltage, temperature and LASER efficiencies may vary. The average optical power is always one half of the peak power since the LASER is driven between full on and full off, with an average mark-space ratio of 50%. An example circuit arrangement is shown in figure 6. Adjustment Procedure Select the appropriate LASER drive mode using the pins DP1-5 (see section headed Operational Modes). The LASER drive current and hence transmitted optical power is set by adjusting Rtrc until the required output power is obtained, taking account of the maximum allowed drive current set by the LASER manufac- turer. There are two ways of measuring the output power and drive current, either dynamically in the normal operating mode or statically by setting the pin SETB low. If measuring power dynamically during the normal mode, the output from the laser can be measured using an optical-power meter that is capable of detecting peak optical-power. If an averaging optical power meter is employed then a correction factor of 16 must be used to obtain the peak value : LASER(peak power) = Laser(average power) * 16. To measure power statically, the SETB pin must be pulled low to ground. This forces the device to constantly transmit through the LASER at a fixed level. This fixed level will be equivalent to half of the peak level, since the normal control loop within the device works to control the average power level through integrating out the alternating data pulses. LASER(peak power) = Laser power(with SETB=0) * 2. Since all currents are static in this mode, a simple optical power meter can be used and the drive current in the laser can be easily measured by connecting an ammeter between pin LMN and VA+. LMN provides a convenient means of monitoring the LASER drive current through the relationship : LASER(current) = 100 x LMN(current) +/- 8%. Dynamic measurement of the LMN current is also possible by connecting a resistor to LMN and measuring the voltage pulses. Data-Rate Selection The ACS102A benefits from data compression circuitry which reduces power consumption and improves the BER (Bit Error Rate). The compression technique employed, demands a minimum TxD data-bit time of 10 sample-clocks. This defines the maximum data rate: Maximum data rate = sample-clock/10 However, an allowance must be made for any variation in the TxD data-bit period to accommodate frequency variation and jitter. Hence the maximum data rates specified in the following are decreased by 10% to include a sufficient safety margin. The ACS102A includes an input pulse shaper which ensures that the system is very tolerant to jitter, and helps achieve a maximum data-rate close to the theoretical maximum of sample-clock/10 (bps). The pulse shaper will expand data pulses of less than 10 clock-samples to meet the compression criteria. This is performed on up to three consecutive data-bits which fail to meet the minimum pulse width criteria.

Table 1. TxD Data-Rate Selection Table 1. shows the maximum TxD data rate, which includes a 10% is the reduced power consumption of the device. ACS102A which are often used for the RS-232 handshake signals. and output lines are RII and RIO respectively. data channel, while maintaining low power consumption. XTAL; at 10.0MHz this is approximately 1.6ms. ii. changes detected on RTS and DTR. programmed using pins HD(1:2) in accordance with the Table 2. Table 2. Handshake signal bandwidth allocation section headed Super-Compress mode. Current and Power Consumption for more details. reduces the data by a factor of 1 to 3 depending on the data itself. compression afforded will approach a CF of 3. oscillator and basic 'house-keeping' functions. XTAL frequencies which cause loss of synchronisation. the locking time will differ on each attempt to lock. Table 3. Diagnostic and operational modes synchronisation between the modems is maintained. local and remote loopback, local loopback is selected. synchronisation with a second modem. initiate remote loopback will be ignored. otherwise cause loss of synchronisation.

automatic locking may take tens of seconds or even minutes. a clock derived from a single source (i.e. tolerance of 0ppm). cycle reverts automatically to normal. time. Active lock mode is usually invoked temporarily on power-up. configured in this mode by hard wiring the DM pins. lock mode is compatible with drift lock and active lock. initiate an arbitration process. Table 4. Mixing lock modes 100ms or more. This pin should be connected as figure 4. and the handshake outputs CTS and DSR will be forced High. an effect on the initial locking time and the receiver sensitivity limit. the link thereby forcing the device temporarily out of lock. indication of a high quality link. of pulsing denotes locking status.

function of the efficiency of the display LED, and the power budget. and the lower the power consumption. HD(1:2) input pins. See section headed RS-232 Handshake Signals. consumption is proportional to the frequency of switching. are static and as such are independent of the XTAL frequency. average current and power consumption for details). VD+ and 100µF* for VA+. The configuration can be seen in Figure 1. TxD /GE0RxD, RTS /GE0CTS and DTR /GE0DSR, is shown in Table 5. Table 5. FDD with XTAL = 10MHz ACS102A can support any wavelength LED or LASER. independent power trace to the point where power enters the board. Figures 4 to 6 all show the recommended power supply decoupling. efficiency and the fiber type.

Advanced Communications ACS102A Data Sheet PLCC-

44 Pin

44 Pin Symbol IO Name Description

16 D P 1I Mode

Selects operating mode for use with PPLED, LED/PIN or LASER/PIN. 2 7 GND - Ground Power Supply 3 8 DCDB O Data Carrier Detect Modem control signal - LOW when modems locked

49 R T SI

Send & Data Channel 2 i/p Modem control signal or additional low frequency data channel input 51 0R I OO Ring indicator output An alternative data channel which may be for the propagation of the RS232 Ring indicator signal. 61 1D S RO Data Set Ready & Data Channel 3 o/p Modem control signal or additional low frequency data channel output 71 2 L M N O L a s e r m o n i t o rA pull down current equal to 1/100 th of the Laser current. 8 13 RxD O Received Data Received data 91 4D R 3 I Data Rate Select The DR(1:3) inputs select the Data Rates, see p2. XLI XLO I O Oscillator Crystal Connect fundamental parallel resonance crystal with padding capacitors to GND 12 17 GND - Ground Power Supply ground. 13 18 DP5 I Mode Selection Selects operating mode for use with PPLED, LED/PIN or LASER/PIN. 14 19 VD+ - +ve power supply Power Supply, 3.3-5.25 V olts 15 20 TxD I Transmit Data Transmitted data 16 21 ERL O Error Detector Indicates quality of line. If a coding infringement is detected, ERD goes High. Reset by PORB to Low 17 22 DTR I Data Terminal Ready/Data / Channel 3 i/p Modem contrrol signal or additional low frequency data channel input 18 23 HBT O 'Heart beat' Lock & power up indicator Indicates power up and modem lock, pulses slowly when locked, fast unlocked. 19 24 HD1 I Handshake Delay Sets the Handshake bandwidth, see p4 20 25 CTS O Clear T o Send & Data Channel 2 o/p Modem control signal or additional low frequency data channel output 21 26 HD2 I Handshake Delay Sets the Handshake bandwidth, see p4 22 27 PORB I Power-on- Reset W ill reset the device when PORB = 0. Connect to an RC circuit as in figure 4, so a reset performed on power-up. DR1 DR2 I Data Rate Select The DR(1:3) inputs select the Data Rates, see p3 DM3 DM2 DM1 I Diagnostic Modes DM(1:3) input select for Diagnostic Modes such as local loopback and remote loopback PIN DESCRIPTION PLCC-

44 Pin Sym IO Name Description

constant transmit mode for power adjustm ent. Leave disconnected when using LEDs. 29 34 NSB I New Slice Bar Connect to GND. 30 35 GND - Ground Ground Supply 31 - NC - Not connectedNot connected 32 36 CNT IO Capacitor Integration Integrating capacitor is placed between CNT and GND of value 10nF-47nF with an XTAL of 27-5Mhz - 37 GND - Ground Ground Supply PINN PINP I I PIN Cathode PIN Anode Connections to a PIN diode or LASER monitor diode. LAN LAP IO IO LED Cathode LED Anode Connections to LED or LASER 37 42 V A+ - +ve Supply Power supply, 3.3-5.25 V olts 38 43 CTX IO Capacitor for Laser transm it A 10 nF capacitor is connected between this pin and ground for LASER applications. It is used in m onitoring of the average transm it power. Can be left disconnected when using LEDs. 39 44 TRC I Tr ansmit Current Defines transmit current to the LED. Minimum and maximum values are set by connecting TRC to GND via a resistor, value R defined by equation on page 2. 40 1 RII I Ring indicator input An alternative data channel which may be for the propagation of the RS232 Ring indicator signal. 41 2 DP4 I Mode Selection Selects operating m ode for use with PPLED, LED/PIN or LASER/PIN. 42 3 DP3 I Mode Selection Selects operating m ode for use with PPLED, LED/PIN or LASER/PIN. 43 4 VD+ - +ve Supply Power Supply, 3.3-5.5 V olts 44 5 DP2 I Mode Selection Selects operating m ode for use with PPLED, LED/PIN or LASER/PIN.

Advanced Communications ACS102A Data Sheet Single Fiber link Link Budget Example (Rtrc set so LED launch current = 50mA peak) Fiber type Plastic Glass Glass Fiber size 1000 micron 62.5micron 50 micron Minimum Transmit Couple power to fiber (µW) 1000 60 40 Minimum LED responsivity (A/W) 0.01 0.16 0.16 Minimum ACS102A sensitivity (nA) 500 500 500 Minimum input power to ACS102A amplifier (µW) 50 3.1 3.1 Link Budget (dB) 10 13 11 Average current consumption TxD = 19.2kbps (mA) 3.8 3.8 3.8 Average current consumption TxD = 64kbps (mA) 7.2 7.2 7.2 Dual Fiber link optimised for performance Link Budget Example (Rtrc set so LED launch current = 100mA peak) Fiber type Plastic Glass Glass Fiber size 1000 micron 62.5 micron 50 micron Minimum Transmit Couple power to fiber (µW) 1000 120 80 Minimum PIN responsivity (A/W) 0.1 0.6 0.6 Minimum ACS102A sensitivity (nA) 500 500 500 Minimum input power to ACS102A amplifier (µW) 5 0.83 0.83 Link Budget (dB) 23 21 19.8 Average current consumption TxD = 19.2kbps (mA) 7 7 7 Average current consumption TxD = 64kbps (mA) 14 14 7.6 Dual Fiber link optimised for low power & low cost optical components Link Budget Example (Rtrc set so LED launch current = 12.5mA peak) Fiber type Plastic Glass Glass Fiber size 1000 micron 62.5micron 50 micron Minimum Transmit Couple power to fiber (µW) 125 13 6.5 Minimum PIN responsivity (A/W) 0.1 0.6 0.6 Minimum ACS102A sensitivity (nA) 500 500 500 Minimum input power to ACS102A amplifier (µW) 5 0.83 0.83 Link Budget (dB) 13.9 12 9 Average current consumption TxD = 19.2kbps (mA) 2.2 2.2 2.2 Average current consumption TxD = 64kbps (mA) 3.4 3.4 3.4 Calculating average current and power consumption Average current Iav (mA) = XTAL* 10 -7 (1.3 + 3*(A + U *H ) ) + Itrc (A + U * H) + Iout + Ihbt Power P (mW) = I av (mA) * V Terms used in current/power calculation: XTAL = Crystal Oscillator Frequency, Hz I out = Average current sourced mA H = Handshake on from digital outputs such H=1 for handshakes active as (RxD,CTS,DSR,DCD) H=0 for handshakes at DC level I hbt = Average current sourced mA U = Handshake constant from HBT pin. U = 0.001 when HD 2/1 = 0/0 (see section HBT Status pin) U = 0.028 when HD 2/1 = 0/1 U = 0.014 when HD 2/1 = 1/0 I trc = Peak Transmit current mA U = 0.007 when HD 2/1 = 1/1 set by TRC pin. A = Active window constant A = 0.022 when DR 3/2/1 = 0/1/1 V = Voltage supply to the ACS102 V A = 0.03 when DR 3/2/1 = 1/0/0 Power formula is only accurate A = 0.045 when DR 3/2/1 = 1/0/1 for voltage supply = 5 Volts A = 0.08 when DR 3/2/1 = 1/1/0 A = 0.11 when DR 3/2/1 = 1/1/1 Note : An application note on power extraction from the RS232 lines is available from Acapella. This shows a typical example circuit diagram for powering the ACS102A, the optics and all related circuitry from the RS232 data lines.

For Digital Input pins: TxD, RTS, DTR, PORB, RII, DP, DR(3:1), DM(3:1), HD(2:1). For Digital Output pins: RxD, DSR, CTS, DCDB, ERRL, RIO, HBT. Figure 2. Data and handshake signals transmitted over a single fiber. ratings for an extended period may reduce the reliability or useful lifetime of the product.

Advanced Communications ACS102A Data Sheet Figure 3. Package Dimensions, PLCC44 & TQFP44 PLCC44 D/E D1/E1 D2/E2 D3/E3 A A1 A2 e b R Copl.

PACKAGE INFORMATION

Figure 6. Basic Circuit for a Twin Fiber Link using LASER and PIN.

Advanced Communications ACS102A Data Sheet ISO9001 CERTIFIED Semtech reserves the right to change specifications on catalog devices without notice. © Copyright Semtech Corp 2000

ORDERING INFORMATION

For additional information, contact the following: Semtech Corporation Advanced Communications Products E-Mail: AdvCom@semtech.com Internet: http://www.semtech.com USA: 652 Mitchell Road, Newbury Park, CA 91320-2289 Tel: +1 805 498 2111, Fax: +1 805 498 3804 FAR EAST: 11F, No. 46, Lane 11, Kuang Fu North Road, Taipei, Taiwan, R.O.C. Tel: +886 2 2748 3380, Fax: +886 2 2748 3390 EUROPE: Delta House, Chilworth Research Centre, Southampton, Hants, SO16 7NS, UK Tel: +44 23 80 769008, Fax: +44 23 80 768612 Device Code Package Temperature ACS102A-TQ TQFP44 -40 to 85 °C(ambient) ACS102A-PL PLCC44 -40 to 85 °C(ambient)