02068-DSH-001-C Mindspeed Technologies®April 2006
Mindspeed Proprietary and Confidential
The CX02068 is a highly integrated, programmable laser driver intended for Telecom applications up to 622 Mbps.
Using differential PECL data, the CX02068 supplies the bias and modulation current for driving an edge-emitting
laser. The modulation output can be DC-coupled to the laser diode, giving a significant power saving over AC-
coupled operation.
The CX02068 includes automatic power control (APC) to maintain a constant average laser output power over
temperature and life. In addition, the modulation current is temperature compensated to minimize variation in
extinction ratio over temperature. Output flags indicate laser end of life as well as failure of the APC circuitry to
maintain average output power.
Features
• Rise and fall times <180 ps
• Operates with +3.3 volt supply
• DC or AC-coupled modulation drive.
• Independently programmable laser bias (to 100 mA) and
modulation currents (to 85 mA).
• Automatic laser power control, with programmable temperature
compensation and ‘Slow-Start’.
• Bias and modulation current monitors
• Failure monitor
• Available in BCC+24 , TQFP32 and DIE packages
• Available in RoHS compliant packages
Applications
• OC-3/STM1, SONET/SDH
• OC-12/STM4, SONET/SDH
•ATM
• FTTH
Functional Block Diagram
X100
X55
Failure
Detect
DIS
ENA
55
55 FAIL
X1
OCA
DIN
BIAS MON
MOD MON
OUT-
OUT+
VDD
IBIAS
RMODSET
RTCSLOPE
RTCSTART
RMPCSET
VDD
CMPC
VREF
PD
ROCA
OCA SET
RD
GNDA
RSHUNT
CSHUNT
I BIAS
DIN
IMOD PP
Revision Information
This document contains information that is subject to change without notice. Contact Technical
Publications for latest revision information.
CX02068
3.3 Volt Laser Driver IC for 155/622 Mbps
02068-DSH-001-C Mindspeed Technologies®ii
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Ordering Information
Part Number Package
CX02068B24 BCC+24L
CX02068TQ32 TQFP32
CX02068G-09-T* BCC+24L, RoHS
CX02068G-TQ32* TQFP32, RoHS
CX02068DIEWP Waffle pack
CX02068WAFER Whole 8” wafer on a 10” grip ring
CX02068EVM Evaluation board with a CX02068B24
* The letter “G” designator after the part number indicates that the device is RoHS-compliant. Refer to www.mindspeed.com for additional
information.
Revision History
Revision Level Date ASIC Revision Description
C Preliminary April 2006 x Added RoHS package information, updated format, no specification
changes.
B Preliminary May 2005 x Updated to new data sheet format.
A Advance October 2003 x Advance.
BCC+24L Top View
2
3
4
5
6
78 9 10 11 12 13
14
15
16
17
18
19
24 23 22 21 20
1
ENA
DIS
FAIL
OCA
GND
BIAS
OUT+
OUT-
PD
GND
GND
VCC
GNDA
CMPC
TCSLOPE
TCSTART
MODSET
OCASET
DIN
DIN
VCC
4mm
BIASMON
4mm MODMON
VCC
2068
TQFP32 Top View
1
2
7
6
5
4
3
8
24
23
18
19
20
21
22
17
12
9
10
11
15
14
13
16
29
32
31
30
26
27
28
25
N/C
N/C
N/C
ENA
DIS
FAIL
OCA
GND
PD
OUT-
OUT+
BIAS
VCC
DIN
DIN
VCC
VCC
BIASMON
MOD MON
VCC
VCC
VCC
GND A
GND A
VCC
CMPC
NC
TC SLOPE
GND
MOD SET
OCA SET
VCC
5mm
5mm
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1.0 Product Specification
1.1 Absolute Maximum Ratings
These are the absolute maximum ratings at or beyond which the IC can be expected to fail or be damaged.
Functional operation at these levels is not implied.
1.2 Recommended Operating Conditions
Table 1-1. Absolute Maximum Ratings
Parameter Rating Units
Power supply (VCC-GND) -0.5 to +6.0 V
Operating ambient -40 to +85 °C
Storage temperature -65 to +150 °C
Maximum bias current 120 mA
Maximum laser modulation current
(through OUT+/OUT2+, OUT-/OUT2-)
100 mA
Table 1-2. Recommended Operating Conditions
Parameter Rating Units
Power supply (VCC-GND) 3.3 ± 10% V
Junction temperature (die) -40 to +120 °C
Operating ambient -40 to +85 °C
Product Specification
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1.3 DC Characteristics
VCC=+3.3V ± 10%, TA=-40 °C to +85 °C, unless otherwise noted.
Table 1-3. DC Characteristics
Parameter Conditions Min Typ Max Units
Supply current Excluding IBIAS and IMOD, but with IBIAS
and IMOD set to 50 mA
-42 47 mA
Bias current adjust range Limited by IREF across temperature
range
4- 100 mA
Bias current with output disabled Tx_Dis = HIGH - - 10 µA
Bias current limit adjustment region TA = +85 °C 20 - 100 mA
Change in bias current limit over
temperature
100 - 130 µA/°C
Monitor diode reverse bias voltage 2 - - V
Monitor diode current adjustment range 10 - 1000 µA
TTL/CMOS input HIGH voltage (enable,
disable)
2.0 - - V
TTL/CMOS input LOW voltage (enable,
disable)
-- 0.8 V
CMOS output HIGH voltage (FAIL, OCA) 2.4 - - V
CMOS output LOW voltage (FAIL, OCA) - - 0.4 V
Differential input impedance Data and clock inputs 2.5 - - kΩ
Common-mode input voltage VCC-1.7 - VCC - VIN (Diff)
4
V
Self-biased common mode input voltage Data and clock inputs VCC-1.7 - VCC-0.47 V
Product Specification
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1.4 AC Characteristics
VCC = +3.3V ±10%, TA = -40 °C to +85 °C, unless otherwise noted.
Table 1-4. AC Characteristics
Parameter Conditions Min. Typ. Max. Units.
Differential input voltage =2 x (DIN+HIGH-DIN+LOW)
(clock inputs follow same relationship)
300 - 1860 mV
Modulation current range 5 - 85 mA
Modulation current with output disabled DIS-HIGH - - 300 µA
Programmable range for modulation
current temperature coefficient
Adjustable 500 - 104ppm/°C
Programmable temperature at which
modulation current TC compensation
enables
Programmed by choice of RTCSLOPE 20 - 60 °C
Modulation output rise/fall times 20% to 80% into 25Ω, with matching network - - 180 ps
Overshoot of modulation output current Into 25Ω load, with matching network -10 - +10 %
Modulation output pulse width distortion 1 Measured using alternating 1-0 pattern - - 1201ps
Modulation output deterministic jitter peak-to-peak. Measured into 25Ω load using: 223-1
PRBS at 622 Mbps includes pulse width distortion
- - 140 ps
NOTE:
1. Contact your Mindspeed sales representative concerning availability of parts with a maximum modulation output pulse width distortion of 80 ps
or less
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2.0 Pin Description
2.1 Pin Descriptions
Table 2-1. Pin Descriptions
Pin No
BCC+24
Pin No
TQFP32 Name Function
-18V
CC Power supply. Connect to VCC, do not leave open.
- 22 GNDA Ground to output stage.(inductor to ground to optimize output stage performance)
-32V
CC Power supply. Connect to VCC, do not leave open.
- 5, 6, 8, 27 NC Not connected
-7V
CC Power supply. Connect to VCC, do not leave open.
-25V
CC Power supply. Connect to VCC, do not leave open.
1 9 ENA Bias and modulation output enable (TTL/CMOS). HIGH for normal operation
2 10 DIS Bias and modulation output disable (TTL/CMOS). LOW for normal operation
311BIAS
MON Bias monitor. Connect a resistor between this pin and VCC to monitor. Connect to VCCif not in use.
412MOD
MON Modulation monitor. Connect a resistor between this pin and VCC to monitor. Connect to VCC if not in
use.
513FAIL
Mean power control failure indicator (TTL/CMOS). Goes low when control loop is no longer able to
maintain constant current at PD
614OCA
Over-Current Alarm (TTL/CMOS). Goes low when IBIAS exceeds the preset bias current limit
7 - GND Ground. Connect to VCC, do not leave open.
8 17 BIAS Laser bias current output
91V
CC Power supply. Connect to VCC, do not leave open.
10 19 OUT+ Positive modulation current output. Sinks current when DIN is HIGH.
11 20 OUT- Negative modulation current output. Sinks current when DIN is HIGH.
12 23 GNDA Ground to output stage.(inductor to ground to optimize output stage performance)
13 24 PD Monitor photodiode input. This input is connected to the monitor photodiode anode for automatic
power control.
14 26 CMPC Mean power control dominant pole capacitor
15 15 GND Ground. Connect to VCC, do not leave open.
16 28 TCSLOPE Connecting a resistor between this pin and ground sets the temperature coefficient of IMODSET (using
the internal IC temperature).
Pin Description
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17 - TCSTART Secondary temperature coefficient of IMOD. A resistor on this pin to ground sets the threshold
temperature at which the temperature compensation starts.
18 30 MODSET Modulation current set. Connect a resistor between this pin and ground
19 31 OCASET Over current alarm set. Connect a resistor between this pin and ground
20 4 VCC Power supply. Connect to VCC, do not leave open.
21 2 DIN Positive Data Input (PECL). Self biased.
22 3 DIN Negative Data Input (PECL). Self biased
23 16 VCC Power supply. Connect to VCC, do not leave open.
24 29 GND Ground. Connect to VCC, do not leave open.
Table 2-1. Pin Descriptions (Continued)
Pin No
BCC+24
Pin No
TQFP32 Name Function
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3.0 Functional Description
3.1 Overview
The CX02068 laser driver consists of a high-speed modulation driver and a laser bias generator with mean power
control (MPC). It is optimized for high speed, low power operation at 3.3 V supply.
Figure 3-1. CX02068 Block Diagram
X100
X55
Failure
Detect
DIS
ENA
55
55 FAIL
X1
OCA
DIN
BIAS MON
MOD MON
OUT-
OUT+
VDD
IBIAS
RMODSET
RTCSLOPE
RTCSTART
RMPCSET
VDD
CMPC
VREF
PD
ROCA
OCA SET
RD
GNDA
RSHUNT
CSHUNT
I BIAS
DIN
IMOD PP
Functional Description
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3.2 Features
• Rise and fall times <180 ps
• Operates with +3.3 volt supply
• DC or AC-coupled modulation drive
• Independently programmable laser bias (to 100 mA) and modulation currents (to 85 mA)
• Automatic laser power control, with programmable temperature compensation and ‘Slow-Start’
• Bias and modulation current monitors
• Failure monitor
• Available in BCC+24 , TQFP32 and DIE packages
• Available in RoHS compliant packages
3.3 Modulator
The modulator output stage is designed to drive up to 85 mA in either AC-coupled or DC-coupled mode. DC-
coupled performance depends on the laser used.
The CX02068 modulation output is optimized for driving a 25Ω dynamic load; the minimum required voltage at
OUT+ and OUT- is 0.6 V. To interface with the laser diode, a matching resistor (RD) is required for impedance
matching. An RC shunt network is necessary to compensate for the laser diode parasitic inductance, thereby
improving the optical eye. Typical values are RSHUNT = 51Ω, CSHUNT = 3.3 pF
Any capacitive loading at the cathode of a laser diode will degrade the optical output performance. An inductor is
used to isolate the BIAS pin from the laser cathode.
Figure 3-2. Typical modulation current vs RMODSET(3.3V)
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.1
0 5000 10000 15000 20000 25000 30000 35000
RMODSET (Ω)
IMOD (A)
Functional Description
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3.4 Mean Power Control Loop
To maintain constant average optical power, the CX02068 incorporates a control loop to compensate for the
changes in laser threshold current over temperature and lifetime. A monitor photodiode mounted in the laser
package is used to convert the optical power into a photocurrent. The MPC loop adjusts the laser bias current so
that the monitor current is matched to a reference current set by a single external resistor (RMPCSET). The time
constant of the loop is then determined by CMPC.
Safety logic is provided in order to limit the maximum bias current. The bias current at which the safety logic trips
is set by an external resistor to ground (ROCA) from the OCASET pin. When the bias current limit is reached alarm
flag OCA is asserted LOW. A loop failure alarm is also provided to detect when the bias current can no longer be
adjusted to achieve the desired average optical power.
Figure 3-3. Typical bias current vs RBIASSET (3.3V)
Figure 3-4. Typical limiting current vs ROCA (at 25 °C)
0
20
40
60
80
100
120
0 10000 20000 30000 40000
RBIASSET (Ω)
Bias current (mA)
0
10
20
30
40
50
60
70
80
90
100
0 10000 20000 30000 40000
ROCA (Ω)
IOCA (mA)
Functional Description
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Figure 3-5. Temperature coefficient of IOCA at different ROCA settings
Figure 3-6. Typical Eye Diagram
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0 5000 10000 15000 20000 25000 30000 35000
ROCA (Ω)
Change in IOCA over temperature (mA/°C)
Functional Description
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3.5 Enable Control
The CX02068 incorporates a dual polarity laser driver enable function. When ENA is LOW or DIS is HIGH, both
the bias and modulation currents are off.
3.6 Current Monitors
The CX02068 features bias and modulation current monitor outputs. The BIASMON output sinks a current equal to
nominally 1/55 of the laser bias current (IBIAS). The MODMON output sinks a current equal to nominally 1/55 of the
laser modulation current (IMOD). BIASMON and MODMON should be connected through a pull-up resistor to VCC.
Choose a pull-up resistor value that ensures a voltage at BIASMON greater than VCC -1.6 V and a voltage at
MODMON greater than VCC -1.0 V. These pins should be tied to VCC if not used.
3.7 Slow-Start
For laser safety and reliability, the CX02068 incorporates a slow-start circuit that provides a delay of approximately
200 ns before enabling the laser diode.
3.8 Temperature Compensation
The CX02068 features built in temperature compensation of the modulation current set using external resistors.
Current pulled from TCSLOPE adjusts the slope of the temperature compensation where as current pulled from
TCSTART sets the threshold temperature for the coefficient.
Functional Description
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Figure 3-7. Temperature Compensation Graphs
TCSLOP
E
TCSTART
80mA
0mA
+80°C-40°C
1∆
2
∆
0.035
0.037
0.039
0.041
0.043
0.045
0.047
-40-20 0 20406080100
Temperature (°C)
IMOD (A)
5000 10000 20000 32000
RTCSTART = 0Ω, VCC = 3.3V
RTCSLOPE - Figures shown are in Ω
0.035
0.04
0.045
0.05
0.055
0.06
0.065
-40 -20 0 20 40 60 80 100
Temperature (°C)
IMOD (A)
5000 10000 20000 32000
RTCSTART = 250Ω, VCC = 3.3V
RTCSLOPE - Figures shown are in Ω
0.035
0.04
0.045
0.05
0.055
0.06
0.065
0.07
0.075
0.08
-40 -20 0 20 40 60 80 100
Temperature (°C)
IMOD (A)
5000 10000 20000 32000
RTCSTART = 400Ω, VCC = 3.3V
RTCSLOPE - Figures shown are in Ω
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4.0 Packaging Specification
4.1 Packaging Specification
Figure 4-1. Bare Die Information
BIAS
GNDA
VCCA
OUTP
OUTN
PD
VCC
OCASET
MODSET
GND
MPCSET
TCSTART
TCSLOPE
CMPC
DIN
ENA
DIS
BIASMON
MODMON
FAIL
OCA
OUTP
OUTN
VCCA
GNDA
GNDA
GND
GND
VCC
GND
VCC
GND
DIN
VCC
GND
VCC
VCC
GND
GND
GND
VCC
19
10
20
21
31
32
41
Dimensions:
Pad opening 84 x 84 µm
Die size 1790 x 1718 µm
Die thickness 300 µm ± 10%
Packaging Specification
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Table 4-1. Pad Centers
PIN X Y PIN X Y PIN X Y PIN X Y
ENA -727 440 BIAS -550 -711 VCC 727 -550 GND 550 711
DIS -727 330 GNDA-440 -711 CMPC 727 -440 VCC 440 711
GND -727 220 VCCA -330 -711 GND 727 -33- DIN 330 711
BIASMON -727 110 *OUTP -210 -711 TCSLOPE 727 -220 DIN 220 711
MODMON -727 0 *OUTP -210 -711 GND 727 -110 VCC 110 711
FAIL -727 -110 *OUTN 100 -711 TCSTART 727 0 GND 0 711
GND -727 -220 *OUTN 100 -711 MPCSET 727 110 VCC -110 711
OCA -727 -330 VCCA 220 -711 GND 727 220 VCC -440 711
GND -727 -440 GNDA330 -711 MODSET 727 330 GND -550 711
VCC -727 -550 GNDA440 -711 OCASET 727 440
PD 550 -711 VCC 727 550
Packaging Specification
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Figure 4-2. TQFP32 Package Information
Table 4-2. Package Dimensions
Dimensions Tolerance 5 x 5 x 1.0 mm TQFP, +2.00 mm FP
N Lead count 32
AMax. 1.20
A2 ±0.05 1.00
D ±0.15 7.00
D1 ±0.05 5.00
E ±0.15 7.00
E1 ±0.05 5.00
F1 ±0.10 2.67
F2 ±0.10 2.67
BOTTOM VIEW
Chamfer .203 (4X)
Exposed Pad
F1
F2
PIN 1 ID. 0 0.50P.05
C0.50P.05X45D
/
E1E
D1
D
-B-
-D-
-A-
1
N
TOP VIEW
b
A2 A
DETAIL X
DETAIL A
SIDE VIEW
Packaging Specification
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Figure 4-3. BCC+24L Package Information
Figure 4-4. SMT Mounting Guides
BOTTOM VIEW
"B"
0.50 ± 0.100.50 TYP.
3.15
3.20 "C"
3.20
0.50 TYP.
3.15
2.20
2.20
C.L(PKG.)
C.L(PKG.)
"A"(PIN 1 CORNER)
0.50 ± 0.10
TOP VIEW
0.15
Y
X
4.00 ± 0.10
(PIN 1 CORNER)
4.00 ± 0.10
BCC Pads viewed from above
Corner Pads
Exposed Central Pad (connected to ground plane)
0.4
mm
0.3mm
Pad
0.45mm
0.45mm
Pad
Pad
2.1mm
2.1mm
PCB land
0.1mm
0.1mm
0.1mm
0.1mm
Solder Resist
Mask
0.025mm
0.025mm
0.025mm
PCB land
1.0mm
0.35mm
0.1mm
0.025
mm
0.025
mm
0.025
mm
Solder Resist
Mask
Paste Stencil
1.3mm
0.2mm
0.2mm
PCB land
Lower Right Pad
1.0mm
1.0mm
0.025mm
0.025m
m
0.025mm
0.025mm
0.025m
m
Solder Resist
Mask
Paste Stencil
1.26mm
1.26mm
Paste Stencil
0.55mm
0.55mm
0.125m
m
0.125m
m
W indow
Stencil
0.025mm
0.025mm
0.675mm
0.675mm
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General Information:
Telephone: (949) 579-3000
Headquarters - Newport Beach
4000 MacArthur Blvd., East Tower
Newport Beach, CA 92660
© 2006 Mindspeed Technologies®, Inc. All rights reserved.
Information in this document is provided in connection with Mindspeed Technologies® ("Mindspeed®") products.
These materials are provided by Mindspeed as a service to its customers and may be used for informational
purposes only. Except as provided in Mindspeed’s Terms and Conditions of Sale for such products or in any
separate agreement related to this document, Mindspeed assumes no liability whatsoever. Mindspeed assumes
no responsibility for errors or omissions in these materials. Mindspeed may make changes to specifications and
product descriptions at any time, without notice. Mindspeed makes no commitment to update the information and
shall have no responsibility whatsoever for conflicts or incompatibilities arising from future changes to its
specifications and product descriptions. No license, express or implied, by estoppel or otherwise, to any
intellectual property rights is granted by this document.
THESE MATERIALS ARE PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS OR
IMPLIED, RELATING TO SALE AND/OR USE OF MINDSPEED PRODUCTS INCLUDING LIABILITY OR
WARRANTIES RELATING TO FITNESS FOR A PARTICULAR PURPOSE, CONSEQUENTIAL OR INCIDENTAL
DAMAGES, MERCHANTABILITY, OR INFRINGEMENT OF ANY PATENT, COPYRIGHT OR OTHER
INTELLECTUAL PROPERTY RIGHT. MINDSPEED FURTHER DOES NOT WARRANT THE ACCURACY OR
COMPLETENESS OF THE INFORMATION, TEXT, GRAPHICS OR OTHER ITEMS CONTAINED WITHIN THESE
MATERIALS. MINDSPEED SHALL NOT BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL, OR
CONSEQUENTIAL DAMAGES, INCLUDING WITHOUT LIMITATION, LOST REVENUES OR LOST PROFITS,
WHICH MAY RESULT FROM THE USE OF THESE MATERIALS.
Mindspeed products are not intended for use in medical, lifesaving or life sustaining applications. Mindspeed
customers using or selling Mindspeed products for use in such applications do so at their own risk and agree to
fully indemnify Mindspeed for any damages resulting from such improper use or sale.
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