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19-2605; Rev 0; 10/02
10.7Gbps Compact Laser Diode Driver
General Description
The MAX3934 is a compact +5V or -5.2V laser driver designed to directly modulate a laser diode at data rates up to 10.7Gbps. The driver provides externally programmable laser biasing and modulation currents. DC-coupling with an integrated compensation network, consisting of a series-damping resistor and a shunt RC, makes the MAX3934 ideal for compact subassemblies. The MAX3934 accepts a differential CML or PECL data signal and includes 50 on-chip termination resistors. It delivers a 1mA to 60mA laser bias current and a 20mA to 80mA laser modulation current with a typical edge speed of 25ps (20% to 80%). A high-bandwidth, fully differential signal path is internally implemented to minimize jitter accumulation. Additional features include a data polarity control, bias current, and modulation current monitors. o o o o o o o o o o o
Features
1.30mm x 1.35mm Die Size Integrated Compensation Network Single +5V or -5.2V Power Supply 73mA Supply Current Up to 10.7Gbps (NRZ) Operation Programmable Laser Bias Current Up to 60mA Programmable Modulation Current Up to 80mA Polarity Control 25ps Output Edge Speed CML-/PECL-Compatible Signal Inputs Integrated Input Termination Resistors
MAX3934
Ordering Information
PART MAX3934AE/D MAX3934BE/D TEMP RANGE PINPACKAGE RD/CCOMP** 12/580fF 15/464fF
Applications
Compact Optical Transmitters Add/Drop Multiplexer XFP Modules XENPAK/XPAK Modules
-40C to +85C Dice* -40C to +85C Dice*
*Dice are designed to operate over a -40C to +120C junction temperature (TJ) range, but are tested and guaranteed only at TA = +25C. **See Figure 3.
Typical Application Circuit
VCC
VBIAS VEE VEE VCC VCC SDO+ SDO50 50 VCC IN+ BIASMON VEE BIASSET OUT1OUT1+ VCC VEE
VCC
MAX3934
INPLRT VEE VEE
OUT2+ OUT2BIAS
VCC
MAX3952
10Gbps SERIALIZER
MODMON VCC
MODSET
LB
VMOD REPRESENTS A CONTROLLED IMPEDANCE TRANSMISSION LINE VEE
VEE
VEE
Covered by U.S. Patent number 5,883,910
________________________________________________________________ Maxim Integrated Products
1
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10.7Gbps Compact Laser Diode Driver MAX3934
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (VCC - VEE) ...................................-0.5V to +6.0V Voltage at IN+, IN- ..........................(VCC - 1.2V) to (VCC + 0.5V) PLRT, BIASMON, MODMON ...........(VEE - 0.5V) to (VCC + 0.5V) BIASSET ...........................................(VEE - 0.5V) to (VEE + 2.6V) MODSET ...........................................(VEE - 0.5V) to (VEE + 1.4V) Current into IN+, IN-.......................................-24mA to +30.5mA Current into OUT1+, OUT2+,OUT1-, OUT2-....-20mA to +200mA Current into BIAS ............................................-20mA to +100mA Storage Temperature Range .............................-55C to +150C Operating Junction Temperature Range ...........-55C to +150C Processing Temperature (die) .........................................+400C
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.
ELECTRICAL CHARACTERISTICS
(VCC - VEE = 4.75V to 5.5V, TA = -40C to +85C. Typical values are at VCC - VEE = 5V, IBIAS = 35mA, IMOD = 65mA, and TA = +25C, unless otherwise noted.)
PARAMETER Power-Supply Voltage Power-Supply Current Power-Supply Noise Rejection SIGNAL INPUT Input Data Rates Single-Ended Input Resistance Single-Ended Input Return Loss (Note 1) Single-Ended Input Voltage (DC-Coupled) Single-Ended Input Voltage (AC-Coupled) Differential Input Voltage (DC-Coupled) Differential Input Voltage (AC-Coupled) LASER BIAS Bias Current-Setting Range Bias Sensing Resistor Bias Current Temperature Stability Bias Current-Setting Error (Note 3) Bias Off-Current LASER MODULATION Modulation Current-Setting Range Modulation Sensing Resistor Modulation Current Temperature Stability IMOD RMOD (Note 1) (Note 5) 20 2.7 -480 3 80 3.3 +480 mA ppm/C IBIAS RBIAS (Note 1) IBIAS 10mA, VBIAS < VCC - 1.2V IBIAS = 1mA, VBIAS < VCC - 1.2V BIASSET VEE + 0.4V (Note 3) 1 5.4 -480 -10 -20 6 60 6.6 +480 +10 +20 0.1 mA ppm/C % mA VIS VIS VID VID NRZ To VCC f < 10GHz 10GHz f 15GHz Figure 2a Figure 2b Figure 4 Figure 4 VCC - 1 VCC 0.4 0.2 0.2 42.5 10.7 50 14 8 VCC VCC + 0.4 2.0 1.6 58.5 Gbps dB V V VP-P VP-P SYMBOL VCC - VEE ICC PSNR Excluding IMOD and IBIAS, data inputs AC-coupled (Notes 1, 2) CONDITIONS MIN 4.75 TYP 5 73 20 MAX 5.50 110 UNITS V mA dB
2
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10.7Gbps Compact Laser Diode Driver
ELECTRICAL CHARACTERISTICS (continued)
(VCC - VEE = 4.75V to 5.5V, TA = -40C to +85C. Typical values are at VCC - VEE = 5V, IBIAS = 35mA, IMOD = 65mA, and TA = +25C, unless otherwise noted.)
PARAMETER Modulation Current-Setting Error Modulation Off-Current Output Edge Speed Output Overshoot/Undershoot Driver Random Jitter Driver Deterministic Jitter TTL INPUT Input High Voltage Input Low Voltage Input Current -70 VEE + 2.0 VEE + 0.8 +70 V V A tR , tF RJ DJ SYMBOL CONDITIONS VOUT_+ < VCC - 1.2V (Note 5) MODSET VEE + 0.4V 20% to 80% (Notes 1, 4, 6) (Notes 1, 4, 6) REXT + RD = 20 (Note 1) (Notes 1, 7) -15 0.3 9.7 25 MIN -10 TYP MAX +10 0.2 35 +15 UNITS % mA ps % psRMS psP-P
MAX3934
Note 1: Guaranteed by design and characterization using the circuit shown in Figure 1. Note 2: PSNR = 20 x log[VCC / (IMOD x 20)]. Measured with VCC = 100mVP-P and f 10MHz. Excludes the effect of the external op amp. Note 3: The minimum voltage at the BIAS pad is VEE + 1.85V + (IBIAS x 8). Note 4: The combined driver AC load (on-chip load and off-chip laser load) is 20. Measured using a 10.7Gbps repeating 0000 0000 1111 1111 pattern. Note 5: The minimum voltage at the OUT_+ pad is VEE + 1.65V + (IMOD x RD) (Figure 3). Note 6: The maximum allowed inductance per bond wire is 0.4nH for OUT1, OUT2, VCC, VEE, and 0.5nH for IN. Note 7: Deterministic jitter is defined as the arithmetic sum of PWD (pulse-width distortion) and PDJ (pattern-dependent jitter). Measured using a 10.7Gbps 27 - 1 PRBS with eighty 0s and eighty 1s inserted in the data pattern.
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10.7Gbps Compact Laser Diode Driver MAX3934
VCC BIAS VCC OUT1PATTERN GENERATOR 50 50 IN+
MAX3934A
IN-
OUT1+ OUT2+
39
39 50
39
39
50
VCC VEE -5V
OUT2-
OSCILLOSCOPE EQUIVALENT CIRCUIT IMOD RD 12 IBIAS REXT 8
Figure 1. AC Characterization Circuit
VCC
100mV
1.0V VCC - 0.5V
VCC - 1.0V (a) DC-COUPLED SINGLE-ENDED CML INPUT VCC + 0.4V
800mV VCC 100mV
VCC - 0.4V (b) AC-COUPLED SINGLE-ENDED (CML OR PECL) INPUT
Figure 2. Definition of Input Voltage Swing 4 _______________________________________________________________________________________
10.7Gbps Compact Laser Diode Driver MAX3934
Typical Operating Characteristics
(Typical values at VCC - VEE = 5V, IBIAS = 35mA, IMOD = 65mA, TA= +25C, unless otherwise noted.)
OC-192 OPTICAL EYE DIAGRAM (IMOD = 55mA, IBIAS = 30mA, 223 - 1 PRBS)
MAX3934 toc01
OC-192 ELECTRICAL EYE DIAGRAM (IMOD = 80mA, 223 - 1 PRBS)
MAX3934 toc02
OC-192 ELECTRICAL EYE DIAGRAM (IMOD = 20mA, 223 - 1 PRBS)
MAX3934 toc03
15ps/div
15ps/div
15ps/div
10.31Gbps OPTICAL EYE DIAGRAM (IMOD = 55mA, IBIAS = 30mA, 223 - 1 PRBS)
MAX3934 toc04
10.31Gbps ELECTRICAL EYE DIAGRAM (IMOD = 80mA, 223 - 1 PRBS)
MAX3934 toc05
10.31Gbps ELECTRICAL EYE DIAGRAM (IMOD = 20mA, 223 - 1 PRBS)
MAX3934 toc06
14ps/div
14ps/div
14ps/div
SUPPLY CURRENT vs. MODULATION CURRENT (EXCLUDES BIAS AND MODULATION CURRENTS)
MAX3934 toc07
DETERMINISTIC JITTER vs. MODULATION CURRENT (10.7Gbps, 27 - 1 PRBS + 80CIDS)
MAX3934 toc08
IMOD vs. VMOD
70 60
MAX3934 toc09
120 110 100 SUPPLY CURRENT (mA) 90 80 70 60 50 40 30 20 20 30 40 50 60 70 TA = +25C TA = -40C TA = +85C
20 18 DETERMINISTIC JITTER (psP-P) 16 14 12 10 8 6 4 2 0 TA = +85C TA = +25C TA = -40C
80
IMOD (mA) 20 30 40 50 60 70 80
50 40 30 20 10 0 0 50 100 150 200 250
80
MODULATION CURRENT (mA)
MODULATION CURRENT (mA)
VMOD (mV)
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10.7Gbps Compact Laser Diode Driver MAX3934
Typical Operating Characteristics (continued)
(Typical values at VCC - VEE = 5V, IBIAS = 35mA, IMOD = 65mA, TA= +25C, unless otherwise noted.)
IBIAS vs. VBIAS
MAX3934 toc10
POWER-SUPPLY NOISE REJECTION vs. FREQUENCY
MAX3934 toc11
DIFFERENTIAL S11 vs. FREQUENCY
-5 -10 -15 |S11| (dB) -20 -25 -30 -35
MAX3934 toc12
60 50 40
40 35 30 PSNR (dB)
0
IBIAS (mA)
25 20 15 10
30 20 10 0 0 100 200 VBIAS (mV) 300 400
-40 -45 -50 0.1 1 10 100 1000 10,000 0 2 4 6 8 10 12 14 16 18 20 FREQUENCY (kHz) FREQUENCY (GHz)
5 0
Pad Description
PAD 1-5, 17-20 6 7 8, 9, 11, 13, 21, 22, 27 10 12 14 15 16 23, 26 24, 25 28 NAME VEE BIASSET BIASMON VCC IN+ INPLRT MODMON MODSET OUT2-, OUT1OUT2+, OUT1+ BIAS FUNCTION Negative Supply Voltage. All pads must be connected to VEE. Bias Current Set. Connected to the output of an external op amp (see the Design Procedure section). Bias Current Monitor (VBIASMON - VEE) / RBIAS = IBIAS Positive Supply Voltage. All pads must be connected to VCC. Positive Data Input. CML/PECL with 50 integrated termination resistor. Negative Data Input. CML/PECL with 50 integrated termination resistor. Differential Data Polarity Swap Input. TTL. Set high or floating for normal operation. Set low to invert the differential signal polarity. Modulation Current Monitor (VMODMON - VEE) / RMOD = IMOD Modulation Current Set. Connected to the output of an external op amp (see the Design Procedure section). Complementary Laser Modulation Current Outputs. Include 20 equivalent on-chip output resistor. Connect both to VCC. Laser Modulation Current Outputs. Include integrated damping resistor and provide laser modulation current (sinking). Connect both to laser diode cathode. Laser Bias Current Output (Sinking)
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10.7Gbps Compact Laser Diode Driver MAX3934
PLRT VCC OUTVCC
VCC 50 IN+ 50
20
MAX3934
RD RCOMP 50 BIAS CCOMP LB 8 IBIAS PART MAX3934A MAX3934B RD CCOMP 12 580fF 15 464fF VEE OUT+ ILD
IN-
50 50 IMOD VCC
VCC
RMOD 3
645
RBIAS 6
645
MODSET VEE
MODMON BIASSET VEE
BIASMON
Figure 3. Functional Diagram
VID = 0.2VP-P TO 2.0VP-P (DC-COUPLED) VID = 0.2VP-P TO 1.6VP-P (AC-COUPLED)
(IN+) - (IN-)
ILD
PLRT = HIGH
PLRT = LOW
IMOD = 20mA TO 80mA IBIAS = 1mA TO 60mA
Figure 4. Required Input Signal and Output Polarity
Detailed Description
The MAX3934 laser driver consists of two main parts, a high-speed modulation driver and a laser-biasing block (see Figure 3). The circuit operates from a single +5V or -5.2V supply. When operating from a +5V supply, connect all V CC pads to +5V and all V EE pads to ground. If operating from a -5.2V supply, connect all VEE pads to -5.2V and all VCC pads to ground. The modulation output stage is composed of a highspeed differential pair and a programmable modulation current source with a maximum modulation current of 80mA. The rise and fall times are typically 25ps. The MAX3934 contains an integrated damping resistor (RD) with the value of 12 or 15 depending on part version. The modulation output is optimized for driving
a 20 load; therefore, the total series load of RD and RLD (where RLD represents the laser diode resistance) should equal 20. At the data rate of 10.7Gbps, capacitive loads at the cathode of a laser diode degrade the optical output performance. Because the BIAS output is directly connected to the laser cathode, use a ferrite bead (LB) with low shunt capacitance to isolate the BIAS pad from the laser cathode.
Polarity Switch
The MAX3934 includes a TTL controlled polarity switch. When the PLRT pad is high or floating, the output maintains the polarity of the input data. When the PLRT pad is low, the output is inverted relative to the input data (see Figure 4).
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10.7Gbps Compact Laser Diode Driver MAX3934
Table 1. Optical Power Relations
PARAMETER Average Power Extinction Ratio Optical Power of a "1" Optical Power of a "0" Optical Amplitude Laser Slope Efficiency Modulation Current SYMBOL PAVG re P1 P0 PP-P IMOD RELATION PAVG = (P0 + P1) / 2 r e = P1 / P 0 P1 = 2PAVG re / (re + 1) P0 = 2PAVG / (re + 1) PP-P = P1 - P0 = 2PAVG(re - 1) / (re + 1) = PP-P / IMOD IMOD = PP-P /
PAVG PP-P OPTICAL POWER P1
P0 TIME
Note: Assuming a 50% average duty cycle and mark density.
Figure 5. Optical Power Definitions
Current Monitors
The MAX3934 features a bias current monitor output (BIASMON) and a modulation current monitor output (MODMON). The voltage at BIASMON is equal to (IBIAS x RBIAS) + VEE, and the voltage at MODMON is equal to (IMOD x RMOD) + VEE, where IBIAS represents the laser bias current, IMOD represents the modulation current, and RBIAS and RMOD are internal 6 and 3 (10%) resistors, respectively. BIASMON and MODMON should be connected to the inverting input of an operational amplifier to program the bias and modulation current (see the Design Procedure section).
the value of VMOD that corresponds to the required modulation current.
Programming the Bias Current
To program the desired laser bias current, connect the inverting input of an op amp (such as the MAX4281) to BIASMON and connect the output to BIASSET. Connect the positive op-amp voltage supply to VCC and the negative supply to VEE (for +5V operation, VCC = +5V and VEE = ground; for -5.2V operation, VCC = ground and VEE = -5.2V). Connect a reference voltage (VBIAS) to the noninverting input of the op amp to set the laser bias current. Refer to the IBIAS vs. V BIAS graph in the Typical Operating Characteristics to select the value of V BIAS that corresponds to the required laser bias current.
Design Procedure
When designing a laser transmitter, the optical output usually is expressed in terms of average power and extinction ratio. Table 1 gives relationships helpful in converting between the optical average power and the modulation current. These relationships are valid if the mark density and duty cycle of the optical waveform are 50%.
External Op-Amp Selection
External op amps are required for regulating the bias and modulation currents. The ability to operate from a single supply with input common-mode range extending to the negative supply rail is critical in op-amp selection. Low bias current and high PSNR are also important. The op-amp gain bandwidth must be high enough to regulate at the power-supply ripple frequency to maintain the PSNR of the laser driver. Filtering the op-amp output is recommended (see the Typical Application Circuit). To maintain stability, the filter capacitor should be smaller than the op-amp capacitive load specification.
Programming the Modulation Current
For a desired laser average optical power (PAVG) and optical extinction ratio (re) the required modulation current can be calculated based on the laser slope efficiency () using the equations in Table 1. To program the desired modulation current, connect the inverting input of an op amp (such as the MAX4281) to MODMON and connect the output to MODSET. Connect the positive op-amp voltage supply to VCC and the negative supply to VEE (for +5V operation, VCC = +5V and VEE = ground; for -5.2V operation VCC = ground and VEE = -5.2V). Connect a reference voltage (VMOD) to the noninverting input of the op amp to set the modulation current. See the IMOD vs. VMOD graph in the Typical Operating Characteristics to select
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Interfacing with Laser Diodes
Refer to Maxim application note HFAN-2.0: Interfacing Maxim Laser Drivers with Laser Diodes for detailed information. The MAX3934 contains an integrated damping resistor (RD) with values of 12 or 15, depending on part version. The modulation output is optimized for driving a 20 load; therefore, the total series load of RD and RLD
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10.7Gbps Compact Laser Diode Driver MAX3934
VCC
OUT1-
OUT1+
OUT2+
OUT2-
50 IN+
50 40 2 RD 2 RD 40
IN-
IMOD VEE
VEE
Figure 6. Equivalent Input Circuit
Figure 7. Equivalent Output Circuit
(where R LD represents the laser diode resistance) should equal 20. In some applications (depending on the laser diode parasitic inductance), an RF matching network at the laser cathode improves the optical output. For best performance, place a bypass capacitor as close as possible to the anode of the laser diode.
OUT1, OUT2, VCC, and VEE as short as possible. This is crucial for optimal performance. Both modulation outputs (OUT1+, OUT2+) must be bonded to the laser diode cathode for proper operation.
Layout Considerations
Use good high-frequency layout techniques and multilayer boards with an uninterrupted ground plane to minimize EMI and crosstalk. Use controlled impedance lines for the data inputs. Power-supply decoupling should be placed as close to the die as possible. Wafer capacitors are required to filter the VEE supplies on both sides of the die. Connect the backside of the die to VCC.
Applications Information
Interfacing to CML and PECL Outputs
The MAX3934 data input accepts CML or PECL signals, but care must be taken to maintain proper biasing and common-mode voltages. Refer to Figure 6 and the Maxim application note HFAN-01.0: Introduction to LVDS, PECL, and CML for additional information.
Laser Safety and IEC 825
Using the MAX3934 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.
Wire-Bonding Die
For high-current density and reliable operation, the MAX3934 uses gold metalization. Make connections to the die with gold wire only, using ball-bonding techniques. Minimize bond-wire lengths and ensure that the span between the ends of the bond wire does not come closer to the edge of the die than two times the bond-wire diameter. The minimum length of the bond wires might be constrained by the type of wire bonder used, as well as the dimensions of the die. To minimize inductance, keep the connections from
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10.7Gbps Compact Laser Diode Driver MAX3934
Table 2. Bondpad Locations
PAD 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 NAME VEE VEE VEE VEE VEE BIASSET BIASMON VCC VCC IN+ VCC INVCC PLRT MODMON MODSET VEE VEE VEE VEE VCC VCC OUT2OUT2+ OUT1+ OUT1VCC BIAS COORDINATES (m) X 16 16 16 16 16 16 16 226 338 450 562 674 786 898 946 946 946 946 946 946 954 828 704 576 408 282 156 30 Y 711 599 487 375 263 151 39 -46 -46 -46 -46 -46
OUT1+ (25) OUT2+ (24) OUT1- (26) BIAS (28) VCC (27) VCC (22)
Chip Topology/ Pad Configuration
The origin for pad coordinates is defined as the bottom left corner of the bottom left pad. All pad locations are referenced from the origin and indicate the center of the pad where the bond wire should be connected. Refer to Maxim application note HFAN-08.0.1: Understanding Bonding Coordinates and Physical Die Size for detailed information. The die size is 51mil x 53mil (1.30mm x 1.35mm) with 3mil (76m) octagonal pads and 4mil (102m) square pads. The die thickness is 8 mils (203m).
Chip Topology
OUT2- (23) VCC (21)
-46 -46 105 217 329 441 553 665 901 901 901 901 901
VEE (1) VEE (2) VEE (3) VEE (4) VEE (5) BIASSET (6) BIASMON (7)
VEE (20) VEE (19)
51 mils
VEE (18) (1.30mm) VEE (17) MODSET (16) MODMON (15)
IN+ (10)
VCC (11)
IN- (12)
VCC (8)
VCC (9)
VCC (13)
901 901 901
DIE COORDINATE ORIGIN
53 mils (1.35mm)
Chip Information
TRANSISTOR COUNT: 884 SUBSTRATE: SOI PROCESS: SiGe BIPOLAR DIE THICKNESS: 8 mils
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
10 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
PLRT (14)

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