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19-4769; Rev 0a; 9/98
KIT ATION EVALU BLE AVAILA
+3.3V, 2.5Gbps SDH/SONET Laser Driver with Automatic Power Control
General Description Features
o Single +3.3V or +5V Power Supply o 62mA Supply Current at +3.3V o Programmable Modulation Current from 5mA to 60mA o Programmable Bias Current from 1mA to 100mA o Rise/Fall Time < 90ps o Automatic Average Power Control with Failure Monitor o Complies with ANSI, ITU, and Bellcore SDH/SONET Specifications o Enable Control
MAX3867
The MAX3867 is a complete, single +3.3V laser driver for SDH/SONET applications up to 2.5Gbps. The device accepts differential PECL data and clock inputs and provides bias and modulation currents for driving a laser. The synchronizing input latch can be bypassed if a clock signal is not available. An automatic power control (APC) feedback loop is incorporated to maintain a constant average optical power over temperature and lifetime. The wide modulation current range of 5mA to 60mA and bias current of 1mA to 100mA are easy to program, making this product ideal for use in various SDH/SONET applications. The MAX3867 also provides enable control, a programmable slow-start circuit to set the laser turn-on delay, and a failure-monitor output to indicate when the APC loop is unable to maintain the average optical power. The MAX3867 is available in a small 48-pin TQFP package as well as dice.
Ordering Information
PART MAX3867ECM MAX3867E/D TEMP. RANGE -40C to +85C -40C to +85C PIN-PACKAGE 48 TQFP Dice*
Applications
SONET/SDH Transmission Systems Add/Drop Multiplexers Digital Cross-Connects Section Regenerators 2.5Gbps Optical Transmitters
*Dice are designed to operate over this range, but are tested and guaranteed at TA = +25C only. Contact factory for availability.
Pin Configuration appears at end of data sheet.
Typical Operating Circuit
+3.3V ENABLE LATCH +3.3V FAIL LD *FERRITE BEAD 20 0.056F SERIALIZER WITH CLOCK GEN. 84.5 84.5 84.5 84.5 CLK+ CLKMD BIASMAX MODSET APCFILT APCSET CAPC 1000pF
124
124
124
124 DATA+
25
OUTOUT+
MAX3890
DATA-
MAX3867
BIAS
________________________________________________________________ Maxim Integrated Products
1
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+3.3V, 2.5Gbps SDH/SONET Laser Driver with Automatic Power Control MAX3867
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, VCC............................................. -0.5V to +7.0V Current into BIAS ...........................................-20mA to +150mA Current into OUT+, OUT- ................................-20mA to +100mA Current into MD.....................................................-5mA to +5mA Voltage at DATA+, DATA-, CLK+, CLK-, ENABLE, LATCH, FAIL, SLWSTRT.........-0.5V to (VCC + 0.5V) Voltage at APCFILT, CAPC, MODSET, BIASMAX, APCSET ...........................................-0.5V to +3.0V Voltage at OUT+, OUT-.............................+1.5V to (VCC + 1.5V) Voltage at BIAS .........................................+1.0V to (VCC + 0.5V) Current into FAIL ...............................................-10mA to +30mA Continuous Power Dissipation (TA = +85C) TQFP (derate 20.8mW/C above +85C) ...................1354mW Storage Temperature Range .............................-65C to +165C Operating Junction Temperature Range ...........-55C to +150C Processing Temperature (die) .........................................+400C Lead Temperature (soldering, 10sec) .............................+300C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
DC ELECTRICAL CHARACTERISTICS
(VCC = +3.14V to +5.5V, TA = -40C to +85C. Typical values are at VCC = +3.3V, IMOD = 30mA, IBIAS = 60mA, and TA = +25C, unless otherwise noted.) (Note 1) PARAMETER Supply Current Bias Current Range Bias Off Current Bias-Current Stability Bias-Current Absolute Accuracy Differential Input Voltage Common-Mode Input Voltage Clock and Data Input Current TTL Input High Voltage (ENABLE, LATCH) TTL Input Low Voltage (ENABLE, LATCH) TTL Output High Voltage FAIL TTL Output Low Voltage FAIL Monitor-Diode Reverse Bias Voltage Monitor-Diode DC Current Range Monitor-Diode Bias Setpoint Stability Monitor-Diode Bias Absolute Accuracy Note 1: Note 2: Note 3: Note 4: Note 5: Note 6: 2 IMD (Note 6) (Note 5) IMD = 1mA IMD = 18A -15 Sourcing 50A Sinking 100A 2.4 0.1 1.5 18 -480 50 90 15 1000 480 VCC - 0.3 (Note 5) VID VICM IIN SYMBOL ICC IBIAS IBIAS-OFF (Note 2) (Note 3) ENABLE = low (Note 4) APC open loop, IBIAS = 100mA APC open loop, IBIAS = 1mA APC open loop Figure 1 PECL compatible -15 200 VCC 1.49 -1 2.0 0.8 VCC 0.44 VCC 1.32 230 900 15 1600 VCC VID/4 10 1 CONDITIONS MIN TYP 62 MAX 105 100 100 UNITS mA mA A ppm/C % mVp-p V A V V V V V A ppm/C %
Characteristics at -40C guaranteed by design and characterization. Dice are tested at TA = +25C only. Tested at RMODSET = 2.49k, RBIASMAX = 1.69k, excluding IBIAS and IMOD. Voltage on BIAS pin is (VCC - 1.6V). Both the bias and modulation currents will be switched off if any of the current set pins are grounded. Accuracy refers to part-to-part variation. Assuming that the laser to monitor-diode transfer function does not change with temperature.
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+3.3V, 2.5Gbps SDH/SONET Laser Driver with Automatic Power Control
AC ELECTRICAL CHARACTERISTICS
(VCC = +3.14V to +5.5V, load as shown in Figure 2, TA = -40C to +85C. Typical values are at VCC = +3.3V, IMOD = 30mA, and TA = +25C.) (Note 7) PARAMETER Input Latch Setup Time Input Latch Hold Time Modulation-Current Range Modulation-Off Current Modulation-Current Stability Modulation-Current Absolute Accuracy Output Rise Time Output Fall Time Output Aberrations Enable/Start-Up Delay Maximum Consecutive Identical Digits Pulse-Width Distortion Jitter Generation PWD (Notes 8, 9) Jitter BW = 12kHz to 20MHz, 0-1 pattern 80 9 7 50 20 tR tF SYMBOL tSU tH IMOD IMOD-OFF ENABLE = low (Note 4) IMOD = 60mA IMOD = 5mA (Note 6) 20% to 80% (Note 8) 20% to 80% (Note 8) (Note 8) MAX3867ECM MAX3867C/D MAX3867ECM MAX3867C/D -15 79 69 88 79 15 250 (Note 10) -480 -50 250 15 CONDITIONS LATCH = high, Figure 3 LATCH = high, Figure 3 MIN 100 100 5 60 200 480 TYP MAX UNITS ps ps mA A ppm/C % ps ps % ns bits ps psp-p
MAX3867
Note 7: AC characteristics are guaranteed by design and characterization. Note 8: Measured with 622Mbps 0-1 pattern, LATCH = high. Note 9: PWD = (wider pulse - narrower pulse) / 2. Note 10: See Typical Operating Characteristics for worst-case distribution.
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3
+3.3V, 2.5Gbps SDH/SONET Laser Driver with Automatic Power Control MAX3867
DATA+ DATA100mV MIN 800mV MAX 200mVp-p MIN
(DATA+) - (DATA-) IOUT+
1600mVp-p MAX
IMOD
Figure 1. Required Input Signal and Output Polarity
VCC
tCLK = 402ps
A A A, B ARE SMD FERRITE BEADS B = BLM11A601S MURATA ELECTRONICS A = BLM21A102S MURATA ELECTRONICS
CLK
tSU
tH
B
B 0.056F
25
MAX3867
OUT0.5pF OUT+ 0.056F BIAS 15 50 50 * OSCILLOSCOPE
DATA
Figure 3. Setup/Hold Time Definition
VCC * TO COMPENSATE PACKAGE LEADS, NOT USED FOR DIE.
Figure 2. Output Termination for Characterization
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+3.3V, 2.5Gbps SDH/SONET Laser Driver with Automatic Power Control
Typical Operating Characteristics
(VCC = +3.3V, load as shown in Figure 2, TA = +25C, unless otherwise noted.)
EYE DIAGRAM (2.488Gbps, 1300nm FP LASER, 1.87GHz FILTER, 48-TQFP)
MAX3867-01
MAX3867
TYPICAL DISTRIBUTION OF FALL TIME
MAX3867-02a
DISTRIBUTION OF FALL TIME (WORST-CASE CONDITIONS)
35 PERCENT IN UNITS (%) 30 25 20 15 10 5 0 MEAN = 111.6ps = 2.9ps 48-TQFP IMOD = 30mA VCC = +3.14V TA = +85C
MAX3867-03a
60 50 PERCENT IN UNITS (%) 40 30 20 10 0 MEAN = 88ps = 3.0ps 48-TQFP IMOD = 30mA
40
50ps/div
80
84
88
92
96
100
FALL TIME (ps)
106 108 110 112 114 116 118 120 122 FALL TIME (ps)
ELECTRICAL EYE DIAGRAM
MAX3867-04a
ELECTRICAL EYE DIAGRAM
MAX3867-05a
RANDOM JITTER vs. IMOD
MAX3867 toc05
0.022 0.020 RANDOM JITTER (UIp-p) 0.018 0.016 0.014 0.012 0.010 JITTER BW = 12kHz to 20MHz 1-0 PATTERN 4 11 18 25 32 39 46 53
26mV /div PATTERN = 213 - 1 + 80 CID IMOD = 30mA 48-TQFP
55mV /div PATTERN = 213 - 1 + 80 CID IMOD = 60mA 48-TQFP
50ps/div
50ps/div
60
IMOD (mA)
IBIASMAX vs. RBIASMAX
MAX3867-06
IMOD vs. RMODSET
MAX3867-07
IMD vs. RAPCSET
1.1 1.0 0.9 IMD (mA) 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0
MAX3867-08
120 100 80 60 40 20 0 1 10 RBIASMAX (k) 100
100 90 80 70 IMOD (mA) 60 50 40 30 20 10 0
1.2
IBIASMAX (mA)
300
1
10 RMODSET (k)
100
0.1
1 RAPCSET (k)
10
100
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+3.3V, 2.5Gbps SDH/SONET Laser Driver with Automatic Power Control MAX3867
Typical Operating Characteristics (continued)
(VCC = +3.3V, load as shown in Figure 2, TA = +25C, unless otherwise noted.)
SUPPLY CURRENT vs. TEMPERATURE (EXCLUDE IBIAS, IMOD, 25 LOAD)
90 80 70 PWD (ps) ICC (mA) 60 50 40 30 20 10 0 -40 -15 10 35 60 85 TEMPERATURE (C) 0. 5 IMOD = 30mA IBIAS = 45mA 5 VCC = +3.3V 15 VCC = +5V
MAX3867-09
PULSE-WIDTH DISTORTION vs. IMOD
MAX3867-10
100
25
20 VCC = +3.3V
10 VCC = +5V
10
20
30 IMOD (mA)
40
50
60
Pin Description
PIN 1, 42, 45 2, 7, 12, 15, 16, 3, 6, 8, 11, 18 4 5 9 10 13 14 17 19 21, 26, 28, 31, 39, 41, 43 22 20, 23, 33 24, 27, 32 6 NAME GND2 GND1 VCC1 DATA+ DATACLK+ CLKLATCH ENABLE SLWSTRT FAIL N.C. APCFILT GND4 VCC4 Ground for internal reference Ground for digital circuits Power supply for digital circuits Positive PECL Data Input Negative PECL Data Input Positive PECL Clock Input. Connect to VCC if latch function is not used. Negative PECL Clock Input. Leave unconnected if latch function is not used. TTL/CMOS Latch Input. High for latched data, low for direct data. TTL/CMOS Enable Input. High for normal operation, low to disable laser bias and modulation currents. A capacitor from this pad to ground delays the turn-on time of laser bias and modulation currents. TTL/CMOS output. Indicates APC failure when low. No Connection. Leave unconnected. Connect a capacitor (CAPCFILT = 0.1F) from this pad to ground to filter the APC noise. Ground for output circuitry Power Supply for output circuitry FUNCTION
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+3.3V, 2.5Gbps SDH/SONET Laser Driver with Automatic Power Control
Pin Description (continued)
PIN 25 29 30 35 34, 36, 40 37 38 44 46 47 48 NAME BIAS OUT+ OUTMD GND3 VCC3 CAPC APCSET MODSET BIASMAX VCC2 Laser Bias Current Output Positive Modulation-Current Output. IMOD flows through this pad when input data is high. Negative Modulation-Current Output. IMOD flows through this pad when input data is low. Monitor Diode Input. Connect this pad to a monitor photodiode anode. A capacitor to ground is required to filter high-speed AC monitor photocurrent. Ground for APC Power Supply for APC A capacitor connected from this pad to ground controls the dominant pole of the APC feedback loop. (CAPC = 0.1F) A resistor connected from this pad to ground sets the desired average optical power. Connect 100k from this pad to ground if APC is not used. A resistor connected from this pad to ground sets the desired modulation current. A resistor connected from this pad to ground sets the maximum bias current. The APC function can subtract from this maximum value, but can not add to it. Power Supply for internal reference FUNCTION
MAX3867
_______________Detailed Description
The MAX3867 laser driver consists of two main parts: a high-speed modulation driver and a laser-biasing block with Automatic Power Control (APC). The circuit design is optimized for both high-speed and low-voltage (+3.3V) operation. To minimize the pattern-dependent jitter of the input signal at speeds as high as 2.5Gbps, the device accepts a differential PECL clock signal for data retiming. When LATCH is high, the input data is synchronized by the clock signal. When LATCH is low, the input data is directly applied to the output stage. The output stage is composed of a high-speed differential pair and a programmable modulation current source. Since the modulation output drives a maximum current of 60mA into the laser with an edge speed of 100ps, large transient voltage spikes can be generated due to the parasitic inductance. These transients and the laser forward voltage leave insufficient headroom for the proper operation of the laser driver if the modulation output is DC-coupled to the laser diode. To solve this problem, the MAX3867's modulation output is designed to be AC-coupled to the cathode of a laser diode. An external pull-up inductor is necessary to DC-bias the modulation output at VCC. Such a configuration isolates laser forward voltage from the output circuitry and
allows the output at OUT+ to swing above and below the supply voltage VCC. A simplified functional diagram is shown in Figure 4. The MAX3867 modulation output is optimized for driving a 25 load; the minimum required voltage at OUT+ is 2.0V. Modulation current swings of 80mA are possible, but due to minimum power supply and jitter requirements at 2.5Gbps, the specified maximum modulation current is limited to 60mA. To interface with the laser diode, a damping resistor (R D) is required for impedance matching. An RC shunt network is also necessary to compensate for the laser-diode parasitic inductance, thereby improving the optical output aberrations and duty-cycle distortion. At the data rate of 2.5Gbps, any capacitive load at the cathode of a laser diode will degrade the optical output performance. Since the BIAS output is directly connected to the laser cathode, minimize the parasitic capacitance associated with this pin by using an inductor to isolate the BIAS pin from the laser cathode.
Automatic Power Control
To maintain constant average optical power, the MAX3867 incorporates an APC loop to compensate for the changes in laser threshold current over temperature and lifetime. A back-facet photodiode mounted in the
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+3.3V, 2.5Gbps SDH/SONET Laser Driver with Automatic Power Control MAX3867
VCC
LATCH
MAX3867
OUT+ 0 DATA CLK D Q 1 MUX OUTIMOD
LP CD RD
CF RF
LP
25
ENABLE IBIAS BIAS
VCC
172X 5X
40X
MD 1000pF IMD FAILURE DETECTOR
MODSET RMODSET
BIASMAX FAIL RBIASMAX
CAPC CAPC
APCSET RAPCSET
Figure 4. Functional Diagram
laser package is used to convert the optical power into a photocurrent. The APC loop adjusts the laser bias current so that the monitor current is matched to a reference current set by RAPCSET. The time constant of the APC loop is determined by an external capacitor (CAPC). To eliminate the pattern-dependent jitter associated with the APC loop-time constant, and to guarantee loop stability, the recommended value for CAPC is 0.1F. When the APC loop is functioning, the maximum allowable bias current is set by an external resistor, RBIASMAX. An APC failure flag (FAIL) is set low when the bias current can no longer be adjusted to achieve the desired aver8
age optical power. To filter out the APC loop noise, use an external capacitor at APCFILT with a recommended value of 0.1F. APC closed-loop operation requires the user to set three currents with external resistors connected between ground and BIASMAX, MODSET, and APCSET. Detailed guidelines for these resistor settings are described in the Design Procedure section.
Open-Loop Operation
If necessary, the MAX3867 is fully operational without APC. In this case, the laser current is directly set by two external resistors connected from ground to BIASMAX
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+3.3V, 2.5Gbps SDH/SONET Laser Driver with Automatic Power Control
and MODSET. See the Design Procedure section for more details on open-loop operation.
Programming the Bias Current
When using the MAX3867 in open-loop operation, the bias current is determined by the RBIASMAX resistor. To select this resistor, determine the required bias current at +25C. Refer to the IBIASMAX vs. RBIASMAX graph in the Typical Operating Characteristics and select the value of RBIASMAX that corresponds to the required current at +25C. When using the MAX3867 in closed-loop operation, the RBIASMAX resistor sets the maximum bias current available to the laser diode over temperature and life. The APC loop can subtract from this maximum value but cannot add to it. Refer to the IBIASMAX vs. RBIASMAX graph in the Typical Operating Characteristics and select the value of RBIASMAX that corresponds to the end-of-life bias current at +85C.
MAX3867
Optional Data Input Latch
To minimize input data pattern-dependent jitter, the differential clock signal should be connected to the data input latch, which is selected by an external LATCH control. If LATCH is high, the input data is retimed by the rising edge of CLK+. If LATCH is low, the input data is directly connected to the output stage. When this latch function is not used, connect CLK+ to VCC and leave CLK- unconnected.
Enable Control
The MAX3867 incorporates a laser driver enable function. When ENABLE is low, both the bias and modulation currents are off. The typical laser enable time is 250ns and the typical disable time is 25ns.
Slow-Start
For laser safety reasons, the MAX3867 incorporates a slow-start circuit which provides a programmable delay time for enabling a laser diode. An external capacitor (CSLWSTRT) connected from this pad to ground programs the delay by the equation: tENABLE 100k * (CSLWSTRT + 2.5pF)
Programming the APC Loop
When the MAX3867's APC feature is used, program the average optical power by adjusting the APCSET resistor. To select this resistor, determine the desired monitor current to be maintained over temperature and life. Refer to the IMD vs. RAPCSET graph in the Typical Operating Characteristics and select the value of RAPCSET that corresponds to the required current.
APC Failure Monitor
The MAX3867 provides an APC failure monitor (TTL/CMOS) to indicate an APC loop tracking failure. FAIL is set low when the APC loop can no longer adjust the bias current to maintain the desired monitor current.
Interfacing with the Laser Diode
To minimize optical output aberrations due to the laser parasitic inductance, an RC shunt network is required (Figure 4). If RL represents the laser diode resistance, the recommended total resistance for RD + RL is 25. Starting values for coaxial lasers are RF = 75 and C F = 3.3pF. R F and C F should be experimentally adjusted until the optical output waveform is optimized. A bypass capacitor should also be placed as close to the laser anode as possible, for the best performance.
Short-Circuit Protection
The MAX3867 provides short-circuit protection for the modulation, bias and monitor current sources. If either BIASMAX, MODSET, or APCSET is shorted to ground, the bias and modulation output will be turned off.
Pattern-Dependent Jitter (PDJ)
When transmitting NRZ data with long strings of consecutive identical digits (CID), LF droop can occur and contribute to pattern-dependent jitter. To minimize this
Design Procedure
When designing a laser transmitter, the optical output is usually expressed in terms of average power and extinction ratio. Table 1 gives the relationships that are helpful in converting between the optical average power and the modulation current. These relationships are valid if the average duty cycle of optical waveform is 50% For a given laser power PAVE, slope efficiency , and extinction ration re, the modulation current can be calculated by Table 1. Refer to the IMOD vs. RMODSET graph in the Typical Operating Characteristics and select the value of RMODSET that corresponds to the required current at +25C.
Table 1. Optical Power Definition
PARAMETER Average Power Extinction Ratio Optical Power High Optical Power Low Optical Amplitude Laser Slope Efficiency Modulation Current SYMBOL PAVE re P1 P0 Pp-p IMOD RELATION PAVE = (P0 + P1) / 2 re = P1 / P0 P1 = 2PAVE * re / (re + 1) P0 = 2PAVE / (re + 1) Pp-p = 2PAVE (re - 1) / (re + 1) = Pp-p / IMOD IMOD = Pp-p / 9
Programming the Modulation Current
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+3.3V, 2.5Gbps SDH/SONET Laser Driver with Automatic Power Control
pattern-dependent jitter, three external components must be properly chosen: capacitor CAPC, which dominates the APC loop time constant; pull-up inductor LP; and AC-coupling capacitor CD. To filter out noise effects and guarantee loop stability, the recommended value for CAPC is 0.1F. This results in an APC loop bandwidth of 10kHz or a time constant of 16s. As a result, the pattern-dependent jitter associated with an APC loop time constant can be ignored. The time constant associated with the output pull-up inductor (LP), and the AC-coupling capacitor (CD), will also impact the pattern-dependent jitter. For such a second-order network, the PDJ due to the low frequency cutoff will be dominated by LP. For a data rate of 2.5Gbps, the recommended value for CD is 0.056F. During the maximum CID period t, it is recommended to limit the peak voltage droop to less than 12% of the average (6% of the amplitude). The time constant can be estimated by: -t/ 12% = 1 - e LP LP = 7.8t If LP = LP /25, and t = 100UI = 40ns, then LP = 7.8H. To reduce the physical size of this element (LP), use of SMD ferrite beads is recommended (Figure 2).
MAX3867
Applications Information
The following is an example of how to set up the MAX3867.
Select Laser
A communication-grade laser should be selected for 2.488Gbps applications. Assume the laser output average power is PAVE = 0dBm, minimum extinction ratio is re = 6.6 (8.2dB), the operating temperature is -40C to +85C, and the laser diode has the following characteristics: Wavelength: = 1.3m Threshold Current: TH = 22mA at +25C Threshold Temperature Coefficient: TH = 1.3%/C Laser to Monitor Transfer: MON = 0.2A/W Laser Slope Efficiency: = 0.05mW/mA at +25C
Determine RAPCSET The desired monitor diode current is estimated by IMD = PAVE * MON = 200A. The IMD vs. RAPCSET graph in the Typical Operating Characteristics shows that RAPCSET should be 6.0k. Determine RMODSET To achieve a minimum extinction ratio (re) of 6.6dB over temperature and lifetime, calculate the required extinction ratio at 25C. Assuming re = 20, the peak-to-peak optical power Pp-p = 1.81mW according to Table 1. The required modulation current is 1.81(mW) / 0.05(mW/mA) = 36.2mA. The IMOD vs. RMODSET graph in the Typical Operating Characteristics shows that RMODSET should be 4.8k. Determine RBIASMAX Calculate the maximum threshold current (ITH(MAX)) at T A = +85C and end of life. Assuming I TH(MAX) = 50mA, the maximum bias current should be:
IBIASMAX = ITH(MAX) + IMOD/2 In this example, IBIASMAX = 68.1mA. The IBIASMAX vs. RBIASMAX graph in the Typical Operating Characteristics shows that RBIASMAX should be 3.2k.
Input Termination Requirement
The MAX3867 data and clock inputs are PECL-compatible. However, it is not necessary to drive the MAX3867 with a standard PECL signal. As long as the specified common-mode voltage and the differential voltage swings are met, the MAX3867 will operate properly.
Calculate Power Consumption
The junction temperature of the MAX3867 dice must be kept below +150C at all times. The total power dissipation of the MAX3867 can be estimated by the following: P = VCC * VCC + (VCC - Vf) * IBIAS + IMOD (VCC - 25 * IMOD / 2) where IBIAS is the maximum bias current set by RBIASMAX, IMOD is the modulation current, and Vf is the typical laser forward voltage. Junction temperature = P(W) * 48 (C/W)
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+3.3V, 2.5Gbps SDH/SONET Laser Driver with Automatic Power Control
Modulation Current More than 60mA
At +5V power supply, the headroom voltage for the MAX3867 is significantly improved. In this case, it is possible to achieve a modulation current of more than 60mA with AC-coupling, if the junction temperature is kept below 150C. The MAX3867 can also be DC-coupled to a laser diode when operating at +5V supply; the voltage at OUT+ should be 2.0V for proper operation.
Laser Safety and IEC 825
Using the MAX3867 laser driver alone does not ensure that a transmitter design is compliant with IEC 825. The entire transmitter circuit and component selections must be considered. Each customer must determine the level of fault tolerance required by their application, recognizing that Maxim products are not designed or authorized for use as components in systems intended for surgical implant into the body, for applications intended to support or sustain life, or for any other application where the failure of a Maxim product could create a situation where personal injury or death may occur.
MAX3867
Wire Bonding Die
For high current density and reliable operation, the MAX3867 uses gold metalization. Make connections to the die with gold wire only, using ball-bonding techniques. Wedge bonding is not recommended. Die-pad size is 4 mils (100m) square, and die thickness is 12 mils (300m) mils.
Layout Considerations
To minimize inductance, keep the connections between the MAX3867 output pins and LD as close as possible. Optimize the laser diode performance by placing a bypass capacitor as close as possible to the laser anode. Use good high-frequency layout techniques and multilayer boards with uninterrupted ground planes to minimize EMI and crosstalk.
Pin Configuration
BIASMAX MODSET APCSET
Chip Topography
CLK- VCC1 VCC1 DATA+ GND1 VCC1 CLK+ GND1 DATA- VCC1 GND1 LATCH GND2 VCC2 BIASMAX MODSET GND2 APCSET 0.083" N.C. (2.108mm) GND2 N.C. GND3 N.C. CAPC VCC3 GND3
TOP VIEW
VCC2
GND2
GND2
GND3
CAPC
48 47 46 45 44 43 42 41 40 39 38 37
GND2 GND1 VCC1 DATA+ DATAVCC1 GND1 VCC1 CLK+
VCC3
36 GND3 35 MD 34 GND3 33 GND4
N.C.
N.C.
1 2 3 4 5 6 7 8 9
N.C.
ENABLE GND1 GND1 SLWSTRT VCC1 FAIL GND4 N.C. APCFILT GND4 VCC4 BIAS
MAX3867
32 VCC4 31 N.C. 30 OUT29 OUT+ 28 N.C. 27 VCC4 26 N.C. 25 BIAS
CLK- 10 VCC1 11 GND1 12
13 14 15 16 17 18 19 20 21 22 23 24
SLWSTRT
APCFILT
LATCH
ENABLE
GND1
FAIL
GND4
GND4
VCC1
N.C.
GND1
VCC4
N.C. N.C. OUT- VCCA GND3 VCC4 OUT+ N.C. GND4 MD 0.070" (1.778mm)
TQFP ______________________________________________________________________________________ 11
+3.3V, 2.5Gbps SDH/SONET Laser Driver with Automatic Power Control MAX3867
Package Information
TQFPPO.EPS
Maxim makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does Maxim assume any liability arising out of the application or use of any product or circuit and specifically disclaims any and all liability, including without limitation consequential or incidental damages. "Typical" parameters can and do vary in different applications. All operating parameters, including "typicals" must be validated for each customer application by customer's technical experts. Maxim products are not designed, intended or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the Maxim product could create a situation where personal injury or death may occur.
12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 1998 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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