M02061
3.3 or 5 Volt Laser Driver
The M02061 is a highly integrated, programmable laser driver intended for SFP/SFF modules. Using differential
PECL data inputs, the M02061 supplies the bias and modulation current required to drive an edge-emitting laser.
The modulation output can be DC coupled to the laser diode.
The M02061 includes automatic power control to maintain a constant average laser output power over temperature
and life. In addition, the modulation current can be temperature compensated to minimize variation in extinction ratio
over temperature.
Applications
Features
•
•
•
•
• High-speed operation; suitable for SFP/SFF applications.
Typical rise/fall times of 55 ps.
• Programmable temperature compensation. Modulation output and
bias output can be controlled using a few discrete resistors.
• Supports DDMI (SFF-8472) diagnostics
• DC or AC coupled modulation drive. Up to 100 mA modulation
current available when AC coupled.
• Low overshoot allows high extinction ratio with low jitter
• Automatic laser power control, with “Slow-Start”
• PECL and CML compatible differential data inputs
• Complies with major MSAs (GBIC, SFF, SFF-8472, SFP) including
timing requirements
• Packaged in a QFN24
• 3.3 V or 5 V operation
• Pulse width adjustment
SFP and SFF Modules
1G/2G/4G Fibre Channel modules
Short reach and Metro SONET/SDH
CPRI: 614.4, 1228.8, 2457.6, 3072.0, 4915.2 and 6144.0 Mbit/s
Internal
3.3V reg.
VCC
PWA
VCC3
VCC3
VCC
VCC
SHDWNOUT
Typical Applications Diagram
VCC
Internal Power Bus
SVCC
OUT-
DIN +
Input
Buffer
DIN-
Laser
Driver
Output
Buffer
D - FF
OUT+
GND0
VCC3 -1.3V
IBIASOUT
IPIN
Input
Buffer
V CC
(M02061-21
only)
02061-DSH-001-G
CAPC
DISDLY
TxPwrMON
BIASMON
APCSET
MODMON
Automatic Power Control
(laser bias current)
MODSET
TCSLOPE
VCC3SEL
Modulation
Control
SCB
FAIL
DIS
RESET
Safety
Circuitry with
Latched Fault
TX
Disable
VCC3
(M02061-12
only)
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Ordering Information
Part Number
Package
Pin Confitguration
M02061-12
QFN24
DISDLY function on pin 8
M02061G-12*
QFN24 (RoHS Compliant)
DISDLY function on pin 8
M02061-21
QFN24
SCB function on pin 8
M02061G-21*
QFN24 (RoHS Compliant)
SCB function on pin 8
M02061-EVM
Combination Optical and Electrical Evaluation board
DISDLY function on pin 8
*The G in the part number indicates that this is an RoHS compliant package. Refer to www.mindspeed.com for additional information.
Revision History
Revision
Level
Date
ASIC
Revision
G
Release
July 2012
x
Added recommendation for 100 k Ω pull-up resistor at pin 14 IBIASout when pin 18
SVCC is used to control laser current.
F
Release
February 2010
x
Added CPRI data rates to front page.
Added TJ specification and added equation for TA specification in Table 1-1.
E
Release
February 2006
x
Added information for the M02061-21 with pin SCB instead of pin DISDLY.
D
Release
September
2005
x
Description
New format. Remove 32 pin package information.
Changes to Absolute Maximum Specifications - operating temperature, output voltage.
Changes to Recommended Operating Conditions - VCC, operating temperature.
Changes to DC Characteristics - ICC, VMD, TxPWRmon, logic inputs and outputs, data
inputs, safety logic thresholds.
Changes to AC Characteristics - IMOD, Tr, Tf, jitter.
Added eye diagram, ; corrected rise/fall times.
19
24
VCC
SHDWN OUT
QFN24 Pin Configuration
TCSLOPE
2.5Gbps Electrical Eye Diagram
CAPC
x
VCC3
March 2004
PWA
Preliminary
MOD SET
C
1
18
SVCC
DIN+
OUT-
DIN-
OUT+
VCC3SEL
GND 0
GND, connect to
PCB ground
DIS
FAIL
IBIASOUT
6
13
7
IPIN
12
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APC SET
TXPWRMON
BIASMON
MODMON
SCB/DISDLY
RESET
Conditions: 80mA modulation current, 2^7-1 PRBS
4mm x 4mm
2
1.0 Product Specification
1.1
Absolute Maximum Ratings
Table 1-1.
Absolute Maximum Ratings
Symbol
Parameter
Rating
Units
VCC
Power supply voltage
-0.4 to +6.0
V
TJ
Junction temperature
-40 to +110 1
°C
-0.4 to +4.0
V
Operating ambient temperature
-40 to +95
2
°C
Storage temperature
-65 to +150
°C
VCC3
TA
TSTG
3.3V power supply voltage
IBIASOUT (MAX)
Maximum bias output current
150
mA
IMOD (MAX)
Maximum modulation current
140
mA
0 to VCC3 + 0.4
V
DIN+/-
Data inputs
DIS, SCB, VCC3SEL
Mode control inputs
-0.4 to VCC + 0.4
V
BIASMON, MODMON
Bias and modulation output current mirror
compliance voltage
-0.4 to VCC3 + 0.4
V
IPIN
Photodiode anode voltage
-0.4 to VCC3 + 0.4
V
IPIN
Photo diode current
2
mA
FAIL
Status flags
-0.4 to VCC + 0.4
V
Set inputs
-0.4 to VCC3 + 0.4
V
-0.4 to 1.0
V
PWA, APCSET, MODSET
TCSTART
Temperature compensation start temperature
TCSLOPE
Temperature compensation slope
-0.4 to VCC3 + 0.4
V
Output
-0.4 to VCC + 0.4
V
OUT+, OUT1. QFN package:
Air Velocity θJA
0 m/s
57 ºC/W
1 m/s
50 ºC/W
2.5 m/s
45 ºC/W
The above thermal resistance is based on a 4-layer JEDEC standard board (76.2 x 114.3 mm).
2. The maximum operating ambient temperature is the lesser of 95 °C or TA ≤ TJ(Max) - (θJA (Max) x Q) where Q is the power dissipated
in the M02061.
These are the absolute maximum ratings at or beyond which the IC can be expected to fail or be damaged.
Reliable operation at these extremes for any length of time is not implied.
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Product Specification
1.2
Recommended Operating Conditions
Table 1-2.
Recommended Operating Conditions
Parameter
Power supply (VCC-GND)
Rating
Units
3.3 ± 7.5%
V
or 5.0 + 8%, -5%
Operating ambient
-40 to + 95
1.3
°C
DC Characteristics
(VCC = +3.05V to +3.55V or 4.75V to 5.4V, TA = -40 °C to +95 °C, unless otherwise noted)
Typical values are at VCC = 3.3 V, IBIASOUT = 30 mA, IMOD = 30 mA, TA = 25 °C, unless otherwise noted.
Table 1-3.
DC Characteristics (1 of 3)
Symbol
ICC
IBIAS
Parameter
Supply current excluding
IMOD and IBIAS
Bias current adjust range
Conditions
Minimum
Typical
Maximum
Units
PWA high (no pulse width adjust)
–
35
61
mA
additional current when PWA used
-
1.5
-
additional current when operating from a 5V
supply
-
1.5
-
V(IBIASOUT) > 0.7V
For 3.3V operation with an AC coupled laser
mA
1
100
1
60
For 5.0V operation with a DC coupled laser.
IBIAS(OFF)
Bias current with optical
output disabled
DIS = high
–
–
300
µA
–
100
–
A/A
V(IBIASOUT) > VCC - 1V
Ratio of IBIAS current to
BIASMON current
VMD
Monitor diode reverse bias
voltage
VCC =3.3V
1.5
–
–
V
IMD
Monitor diode current
adjustment range
Adjusted with RAPCSET
10
–
1500
µA
0.95
1
1.25
A/A
100
pF
5.4
V
Ratio of TxPwrMON current
to monitor photodiode
current
CMD_MAX
Maximum monitor
photodiode capacitance for
APC loop stability. Includes
all associated parasitic
capacitances.
TTL/CMOS input high
voltage (DIS)
02061-DSH-001-G
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Product Specification
Table 1-3.
DC Characteristics (2 of 3)
Symbol
Parameter
Conditions
TTL/CMOS input low
voltage (DIS)
Minimum
Typical
Maximum
Units
–
–
0.8
V
CMOS input high voltage
(VCC3SEL, SCB)
2.4
V
CMOS input low voltage
(VCC3SEL, SCB)
1.2
V
Logic output high voltage
(FAIL)
With external 10kΩ pull-up to VCC.
VCC - 0.5
–
–
V
Logic output low voltage
(FAIL)
For 6.8k to 10k Ω resistor when pulled up to
5V.
–
–
0.4
V
Differential input impedance Data inputs
–
6800
–
Ω
VSELF
Self-biased common-mode
input voltage
–
VCC3 - 1.3
–
V
VINCM
Common-mode input
compliance voltage
Data inputs
VCC3 - 1.45
–
VCC3-[VIN(Diff)]/4
V
Differential input voltage
= 2 x (DIN+HIGH - DIN+LOW)
200
–
2400
mVpp
2.5
2.8
3.0
V
3.65
3.9
4.25
V
For 4.7k to 10k Ω resistor when pulled up to
3.3V.
RIN
VIN(DIFF)
(1)
VCC3THL
3.3V supply detection, lower
threshold
VCC3THH(1) 3.3V supply detection,
upper threshold
VCC5THL
5V supply detection, lower
threshold
3.9
4.25
4.65
V
VCC5THH
5V supply detection, upper
threshold
5.4
5.8
6.1
V
VREF1
Reference voltage for
MODSET
1.18
1.3
1.4
V
VAPCSET
Reference voltage for
APCSET
VBL
Bias_OK lower voltage
threshold
02061-DSH-001-G
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V
1.05
V
5
Product Specification
Table 1-3.
DC Characteristics (3 of 3)
Symbol
VBH
Parameter
Conditions
Bias_OK upper voltage
threshold
VFAULTL
Lower voltage threshold for
fault inputs IBIASOUT, OUT+,
CAPC, AND MODSET
FAIL asserts if any of these signals fall below
this value.
VOUT_DIS
Self bias voltage for
IBIASOUT and OUT+
DIS = high
VSHDWNL
SHDWNOUT output low
voltage
DIS = low, ISHDWNOUT ≤ 100uA
VSHDWNH
SHDWNOUT output high
voltage
DIS = low, ISHDWNOUT ≤ 10uA
Minimum
Typical
Maximum
Units
1.45
1.6
1.7
V
300
400
mV
1.65
2.2
V
VCC - 4
V
0.5
VCC - 0.3V
V
NOTES:
1.
When VCC = 5V, VCC3 “supply OK” circuitry monitors the internally regulated 3.3V supply. When VCC = 3.3V, VCC3 “supply OK” circuitry monitors
VCC.
1.4
AC Characteristics
(VCC = 3.05 V to 3.55V or 4.75V to 5.4V, TA = -40 °C to +95 °C, unless otherwise noted)
Typical values are at VCC = 3.3 V, IBIASOUT = 30 mA, IMOD = 30 mA, 25 ohm load and TA = 25 °C, unless otherwise
noted.
Table 1-4.
AC Characteristics (1 of 2)
Symbol
IMOD
IMOD(OFF)
Parameter
Conditions
Modulation current range
3.3V operation, AC coupled, OUT+ and OUT>1.6V
Modulation current with output
disabled
Programmable range for modulation
current temperature coefficient
02061-DSH-001-G
10
–
100
Units
mA
5V operation, DC coupled(1) into a 25Ω load to
VCC - 1.2V. OUT+ and OUT- >1.15V
10
DIS = high
–
–
300
µA
–
100
–
A/A
0
–
104
ppm/°C
Ratio of modulation current to
MODMON current
IMOD-TC
Minimum Typical Maximum
Adjustable using TCSLOPE (2)
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Product Specification
Table 1-4.
AC Characteristics (2 of 2)
Symbol
Parameter
tr
Modulation output rise time
tf
Modulation output fall time
OS
Overshoot of modulation output
current in the off direction.
RJ
Random jitter
DJ
Conditions
Minimum Typical Maximum
20% to 80% into 25 Ω.
Measured using 11110000 pattern at 2.5Gbps
(2)
into 25 Ω load
Deterministic jitter
Measured into 25Ω load,
Gbps
231
Units
–
55
75
ps
–
55
75
ps
--
1
–
%
–
0.8
–
psrms
10
25
10
30
- 1 PRBS at 2.7
pspp
K28.5 pattern at 4.25 Gbps
(includes pulse width distortion3)
NOTES:
1.
Guaranteed by design and characterization.
2.
DC coupled operation at 3.3V is not supported. AC coupled operation at 5V is possible provided the outputs never exceed 6V.
3.
Pulse width distortion is measured single-ended.
1.5
Safety Logic Timing
(SCB pin low, VCC = 3.05 V to 3.55V or 4.7V to 5.4V, TA = -40 °C to +95 °C, unless otherwise noted)
Table 1-5.
Safety Logic Timing (1 of 2)
Symbol
Parameter
Conditions
Minimum Typical Maximum
Units
t_off
DIS assert time
Rising edge of DIS to fall of output signal
below 10% of nominal(1)
10
μs
t_on
DIS negate time
Falling edge of DIS to rise of output signal
above 90% of nominal(1)
1
ms
t_init
Time to initialize(2)
Includes reset of FAIL; from power on after
Supply_OK or from negation of DIS during
reset of FAIL condition
5
ms
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Product Specification
Table 1-5.
Safety Logic Timing (2 of 2)
Symbol
Parameter
Conditions
Minimum Typical Maximum
Units
t_fault
Laser fault time - from fault condition From occurrence of fault condition or when
to assertion of FAIL
Supply_OK is beyond specified range
100
μs
t_reset
DIS time to start reset
DIS pulse width required to initialize safety
circuitry or reset a latched fault
10(3)
μs
tVCC_OK
Supply_OK delay time
Delay between Supply_OK condition and when
outputs are enabled
t_onBM
DIS negate (turn-on) time during
burst-mode operation
IMOD > 20mA; outputs DC coupled (5V
operation)(4)
300
500
ns
t_offBM
DIS assert (turn-off) time during
burst-mode operation
IMOD > 20mA; outputs DC coupled (5V
operation)
200
500
ns
10
μs
20
NOTES:
1.
With CAPC < 2.2nF
2.
User-adjustable. Specifications reflect timing with no external RESET capacitor.
3.
With < 1nF capacitor from RESET pin to ground.
4.
Imod >12mA
Figure 1-1.
Relationship between Data Inputs and Modulation Outputs
DIN+
100 mV 1200 mV
D IN-
200 mV 2400 mV
V IN(DIFF)
V OUT-
V OUT+
> 1.60V when VCC5_OR high
> 1.15V when VCC5_OR low
GND
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Product Specification
Figure 1-2.
Safety Logic Timing Characteristics, SCB pin low
Slow Rise on Vcc = 5V at Power-up (DIS Low)
Hot Plug (DIS Low)
5V
VCC3
and
VCC5
status
FAIL
DIS
VCC3 and VCC5
“OK”
VCC
3.3V
VCC3
(low)
FAIL
(low)
DIS
(low)
(low)
t_on < 1ms,
(300 μs typ.)
t_on < 1ms,
(300 μs typ.)
LASER
OUTPUT
LASER
OUTPUT
Slow Rise on Vcc=3.3V at Power-up (DIS Low)
Transmitter Enable (DIS transition Low)
3.3V
VCC
3.3V
VCC3
and
VCC5
status
(high)
FAIL
(low)
DIS
(low)
VCC3 and VCC5
“OK”
VCC3
FAIL state at power-up will
depend on pull-up voltage
FAIL
DIS
(low)
(low)
t_on < 1ms,
(300 μs typ.)
LASER
OUTPUT
02061-DSH-001-G
t_on < 1ms,
(300 μs typ.)
LASER
OUTPUT
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Product Specification
Transmitter Disable (DIS transition high)
(high)
VCC3
and
VCC5
status
VCC3 and VCC5
“OK”
Fault
recovery at:
MODSET.
CAPC, OUT+,
or IBout
DIS
DIS
t_off < 10 μs,
(1 μs typ.)
LASER
OUTPUT
Response to Fault
Fault at:
MODSET.
CAPC, OUTP,
or IBout
FAIL
DIS
LASER
OUTPUT
02061-DSH-001-G
Fault
Removed
FAIL remains high
until reset by DIS
going high
FAIL
(low)
FAIL
Fault Recovery Behavior
t_reset,
10 μs,
min.
t_on < 1ms
LASER
OUTPUT
Unsuccessful Fault Reset Attempt
Fault Occurs
Fault Remains
Fault at:
APCSET
t_fault < 100 μs,
(4 μs typ.)
t_init < 5ms,
(3ms typ.)
FAIL
DIS
t_reset,
10 μs,
min.
LASER
OUTPUT
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2.0 Pin Definitions
Table 2-1 lists pin type definitions and descriptions for the M02061 device.
Table 2-1.
M02061 Pin Definitions and Descriptions (1 of 7)
4x4 mm
QFN24 Pin
Number
Pin Name
1
VCC
2
DIN+
Pin equivalent load
Function
Power supply
V CC3
V CC
Positive data input. Self biased. Compatible with AC coupled PECL, AC
coupled CML, and DC-coupled PECL (VCC = 3.3V).
When DIN+ is high, OUT+ sinks current.
V TT
4 kΩ
D IN+, DIN-,
or
CLK+, CLK-
3
DIN-
4
VCC3SEL
See DIN+ drawing
VCC
Negative data input. Self biased Compatible with AC coupled PECL, AC
coupled CML, and DC-coupled PECL (VCC = 3.3V).
VCC3
3.3V VCC Select.
Connect to VCC3 for VCC = 3.3V operation.
Connect to GND for VCC = 5V operation.
VCC5_ OR
190 Ω
72 kΩ
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Pin Definitions
Table 2-1.
M02061 Pin Definitions and Descriptions (2 of 7)
4x4 mm
QFN24 Pin
Number
Pin Name
5
DIS
Pin equivalent load
Function
Bias and modulation output disable (TTL/CMOS).
V CC
V CC3
7 kΩ
DIS
80 kΩ
6
FAIL
Safety circuit control failure output (TTL/CMOS). Goes high when a safety
logic fault is detected. This output will be low when DIS is high.
VCC
FAIL
7
RESET
VCC3
V
CC
Safety circuit reset. Leave open for normal operation or add a capacitor to
ground to extend the reset time.
Connect to GND to disable window comparators at APCSET
RESET
190 Ω
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Pin Definitions
Table 2-1.
M02061 Pin Definitions and Descriptions (3 of 7)
4x4 mm
QFN24 Pin
Number
Pin Name
8
SCB
(M02061-21
only)
Pin equivalent load
VCC
V CC3
Function
Safety Circuit Bypass. Connect to GND or leave open for normal operation.
Connect to VCC to allow the bias and modulation outputs to operate even if
the safety circuitry indicates a fault.
SCB
24 kΩ
48 kΩ
8
DISDLY
Disable delay control. Connect to ground for normal operation. In burst mode
operation add a capacitor from this pin to ground to set the maximum disable
time. Disable times greater than this maximum will engage the “slow-start”
circuitry.
V CC
(M02061-12
only)
DISDLY
190 Ω
9
MODMON
V CC
VCC3
Modulation Current Monitor. Connect directly through a resistor to GND
(MONPOL high) or to VCC3 (MONPOL low). The current through this pin is
approximately 1/100th of the MODULATION current to the laser.
This pin may be left open if the feature is not needed and the M02061 current
consumption will be reduced by 0.5mA typically.
MOD MON
190 Ω
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Pin Definitions
Table 2-1.
M02061 Pin Definitions and Descriptions (4 of 7)
4x4 mm
QFN24 Pin
Number
Pin Name
Pin equivalent load
Function
10
BIASMON
See MODMON drawing
Bias Current Monitor. Connect directly through a resistor to GND (MONPOL
high) or to VCC3 (MONPOL low). The current through this pin is approximately
1/100th of the BIAS current to the laser.
This pin may be left open if the feature is not needed and the M02061 current
consumption will be reduced by 0.5mA typically.
11
TxPwrMON
VCC
VCC3
Transmit Power Monitor. Connect directly through a resistor to GND
(MONPOL high) or to VCC3 (MONPOL low). The current through this pin is
approximately the same as the photo diode current into IPIN.
This pin may be left open if the feature is not needed and the M02061 current
consumption will be reduced by the IPIN current.
TxPwr MON
33 Ω
12
APCSET
V CC
VCC3
Average Power Control, laser bias current adjustment. Connect a resistor
between this pin and ground to set the bias current to the laser.
The APC loop will control the laser bias current to maintain a voltage of
approximately 1.3V at this pin. The current through this pin is approximately
the same as the current into IPIN.
APCSET
13
IPIN
Current input from monitor photodiode anode.
VCC
The APC loop will adjust the laser bias current to maintain a voltage at
APCSET of approximately 1.3V and at this pin of approximately one VGS. The
voltage at this pin will not exceed 1.6V in normal operation
IPIN
30 Ω
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Pin Definitions
Table 2-1.
M02061 Pin Definitions and Descriptions (5 of 7)
4x4 mm
QFN24 Pin
Number
Pin Name
14
IBIASOUT
Pin equivalent load
Function
Laser bias current output.
VCC
Connect directly to laser cathode or at higher bit rates through a ferrite or a
resistor to isolate the capacitance of this pin from the modulation drive,
(~2pF).
Maintain a voltage > 0.7V at this pin.
IBIASOUT
15
GNDO
V
Connect 100 kΩ pullup resistor to VCC if pin 18 (SVCC) is used.
Ground for output stage. May be connected directly to ground. At high bit
rates (>2Gb/s) an optional inductor or ferrite may be added to reduce
switching transients.
CC
GND0
16
OUT+
Positive modulation current output. Sinks current when DIN+ is HIGH.
VCC
Maintain a voltage > 1.6V at this pin when VCC3SEL is high.
Maintain a voltage > 1.15V at this pin when VCC3SEL is low.
OUT+
GND 0
17
OUT-
See OUT+ drawing
Negative modulation current output. Sinks current when DIN- is HIGH
Maintain a voltage > 1.6V at this pin when VCC3SEL is high.
Maintain a voltage > 1.15V at this pin when VCC3SEL is low.
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Pin Definitions
Table 2-1.
M02061 Pin Definitions and Descriptions (6 of 7)
4x4 mm
QFN24 Pin
Number
Pin Name
18
SVCC
Pin equivalent load
Function
Switched VCC.
VCC
V CC3
3.3V applications - Connect to laser anode. Safety circuitry will open the
switch when a fault is detected and no current will flow through the laser.
No capacitance is needed on this node. If capacitance to ground is added, do
not exceed 100 pF.
SV CC
19
SHDWNOUT
5V applications - Disabled, leave open.
12 kΩ
SHDWNOUT
20
CAPC
External switched VCC control signal. Use in 5V applications to create an
external SVCC.
V CC
Automatic power control loop dominant pole capacitor. (Connect a capacitor
between this pin and VCC3.)
VCC
A 2.2 nF capacitor will give less than 1ms enable time and a loop bandwidth <
30kHz.
C APC
100 Ω
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Pin Definitions
Table 2-1.
M02061 Pin Definitions and Descriptions (7 of 7)
4x4 mm
QFN24 Pin
Number
Pin Name
21
VCC3
Pin equivalent load
Function
3.3V applications - Power supply input. Connect to VCC.
V CC
V CC
5V applications - Internally generated 3.3V. Power supply output. Do not
attach to non-M02061 circuitry.
For 5 V applications add 12 ohms in series with 100 nF to ground at this pin.
V CC3
22
PWA
V CC
Pulse Width Adjust. Connect a resistor to GND to enable, (between 1kΩ and
20kΩ). Connect to VCC3 to disable.
V CC3
+
-
PWA
1.28V
190 Ω
23
MODSET
See PWA drawing
Modulation current control. Connect a resistor to ground to set the
modulation current.
24
TCSLOPE
See PWA drawing
Modulation current temperature compensation coefficient adjustment.
Connect a resistor to ground to set the temperature compensation
coefficient. Leave open to disable the temperature compensation.
A 51 kΩ resistor will result in a temperature compensation slope of
approximately 0.5%/°C.
CENTER
GND
Connect to GND.
PAD
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Pin Definitions
19
24
VCC
SHDWNOUT
CAPC
VCC3
PWA
MODSET
QFN24 Pinout Information
TCSLOPE
Figure 2-1.
1
18
SVCC
DIN+
OUT-
DIN-
OUT+
VCC3SEL
GND 0
GND, connect to
PCB ground
DIS
6
13
02061-DSH-001-G
IPIN
TXPWRMON
BIASMON
MODMON
12
SCB/DISDLY
RESET
7
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APCSET
FAIL
IBIASOUT
4mm x 4mm
18
3.0 Functional Description
3.1
Overview
The M02061 is a highly integrated, programmable laser driver intended for SFP/SFF module with data rates up to
4.25 Gbps. Using differential PECL data inputs, the M02061 supplies the bias and modulation current required to
drive an edge-emitting laser.
Monitor outputs and internal safety logic in the M02061 combined with the M02088 will support designs requiring
DDMI compliance.
The M02061 includes automatic power control to maintain a constant average laser output power over temperature
and life. In addition, the modulation current can be temperature compensated to minimize variation in extinction
ratio over temperature.
Many features are user-adjustable, including the APC (automatic power control) loop bias control (via a monitor
photo diode), modulation current, temperature compensation control of modulation current, and pulse-width
adjustment. The part may be operated from a 3.3V or 5V supply.
The driver modulation output can be AC, DC, or Differentially coupled to the laser.
Safety circuitry is also included to provide a latched shut-down of laser bias and modulation current if a fault
condition occurs. An internal VCC switch provides redundant shutdown when operating the device from a 3.3V
supply. Control is provided to allow for a redundant external switch when operating with a 5V supply, if desired.
Figure 3-1 details the functional blocks and pin signals for the M02061 device.
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Functional Description
Internal
3.3V reg.
SHDWNOUT
PWA
VCC3
M02061 Block Diagram
VCC
Figure 3-1.
Internal Power Bus
SV CC
OUT-
DIN +
Input
Buffer
DIN -
D - FF
Output
Buffer
Laser
Driver
OUT+
GND0
VCC3 -1.3V
IBIAS OUT
IPIN
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CAPC
DISDLY
(M02061-12 only)
TxPwrMON
BIASMON
APCSET
Automatic Power Control
(laser bias current)
MODMON
MODSET
TCSLOPE
Modulation
Control
VCC3SEL
SCB
(M02061-21 only)
FAIL
DIS
02061-DSH-001-G
RESET
Safety
Circuitry with
Latched Fault
TX
Disable
20
Functional Description
Figure 3-2.
2.5Gbps Electrical Eye Diagram
Conditions: 80mA modulation current, 27-1 PRBS
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Functional Description
Figure 3-3.
2.5Gbps Filtered Optical Eye Diagram with NEC NX7315UA Laser
Conditions: 10dB extinction ratio, 33% eye margin, 27-1 PRBS
Figure 3-4.
4.25Gbps Unfiltered Optical Eye Diagram with Archcom AC3460 Laser
Conditions: 7.5dB extinction ratio, 27-1 PRBS
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Functional Description
3.2
Features
•
High speed operation; suitable for SFP/SFF applications from 155Mbps to 4.25 Gbps. Typical rise/fall times of
55 ps.
•
Programmable temperature compensation. Modulation output and bias output can be controlled using a few
discrete resistors.
•
Supports DDMI (SFF-8472) diagnostics when combined with the M02088.
•
DC or AC coupled modulation drive. Up to 100mA modulation current available when AC coupled.
•
Low overshoot allows high extinction ratio with low jitter.
•
Automatic Laser Power Control, with “Slow-Start”.
•
Differential data inputs to minimize pattern dependent jitter, PECL and CML compatible.
•
Packaged in a QFN24
•
3.3V or 5V operation
3.3
General Description
The M02061 is a highly integrated, programmable laser driver intended for SFP/SFF module with data rates up to
4.25 Gbps. Using differential PECL data inputs, the M02061 supplies the bias and modulation current required to
drive an edge-emitting laser. Monitor outputs and internal safety logic support the DDMI requirements.
The M02061 laser driver consists of the following circuitry: an internal regulator, bias current generator and
automatic power control, data inputs, buffer with pulse width adjust, modulation current control, modulator output,
laser fail indication, disable control, and monitor outputs for the bias current, modulation current, and transmitted
power.
3.3.1
Internal Regulator
The M02061 contains an internal 3.3V regulator so high bit rate performance can be achieved with 5V or 3.3V
power supply.
When operating from a 5V supply (VCC is connected to +5V), an internal regulator provides a voltage of
approximately 3.3V to the majority of the on-chip circuitry. The on-chip regulator is internally compensated,
requiring no external components. However, for 5V operation with high modulation currents, it may be necessary to
add 12 ohms in series with 100nF to ground at VCC3 or the internal power supply may dip and cause a fault
condition. When a 3.3V supply is used (VCC and VCC3 connected to 3.3V) the regulator is switched off and the
internal circuitry is powered directly through the VCC3 supply pin. The decision as to whether or not the internal
regulator is required is made via the VCC3SEL pin, which also determines whether the safety circuitry needs to
monitor for proper +5V supply voltage.
For 3.3V applications, SVCC is sourced from VCC3 through a switch (leave SVCC open for 5V applications). SVCC is
to be used to power the anode of the laser diode and the cathode of the photo diode, any resistive or ferrite pull-ups
on the OUT+ and OUT- outputs should be connected directly to VCC. When a fault condition is present, FAIL will
assert and the switch sourcing SVCC will open so no current can pass through the laser. SVCC does not need any
external capacitance, if capacitance to ground is added at SVCC it should be <100 pF. When SVCC is used, add a
100k Ω pullup resistor to VCC at pin 14 (IBIASout).
For 5V operation, an analog switch controlled by SHTDWNOUT can be used to source 5V to the laser anode. In
the case of a fault condition, SHTDWNOUT will go high and open the analog switch which will result in an open
circuit at the laser. SHTDWNOUT is designed to drive a CMOS logic input. An FET transistor may have excessive
Miller capacitance and a fault may be signalled if it turns on too slow.
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Functional Description
VCC and VCC3 status are internally monitored by the M02061 during power-up and normal operation. During
power-up the “slow-start” circuitry requires that VCC and VCC3 each reach an acceptable level before enabling bias
or modulation current.
Table 3-1.
Pin Connection for 3.3V and 5V VCC
Pin Connection For:
Pins Dependent on VCC Voltage
VCC = 3.3V
3.3.2
VCC = 5V
VCC3
Connect to VCC
Reference for CAPC and PWA
SVCC
Laser Anode
OPEN
OPEN
External safety control switch
SHDWNOUT
CAPC
Capacitor between CAPC and VCC3 or VCC Capacitor between CAPC and VCC3 (not VCC)
PWA
Connect to VCC3 or VCC to disable
Connect to VCC3 to disable (not VCC)
Connect to VCC3 or VCC
Connect to GND
VCC3SEL
Bias Current Generator and Automatic Power Control
To maintain constant average optical power, the M02061 incorporates a control loop to compensate for the
changes in laser threshold current over temperature and lifetime. The bias current will be determined by the value
of the external resistor RAPCSET and the transfer efficiency between the laser and monitor photo diode.
The photo current from the monitor photo diode mounted in the laser package is sunk at IPIN. This photo current is
mirrored and an equivalent current is sourced from pins TxPwrMON and APCSET. The APC loop adjusts the laser
bias current (hence the monitor diode photo current) to maintain a voltage at APCSET of 1 band-gap voltage or
~1.3V.
RAPCSET * IPIN = 1.3 V
The APC loop has a time constant determined by CAPC, RAPCSET and the transfer efficiency between the laser and
monitor photo diode. The larger the CAPC capacitor the lower the bandwidth of the loop and the larger RAPCSET the
lower the loop BW.
In general, it is recommended that at least 2.2 nF of external capacitance be added externally between CAPC and
VCC3. With use of a 2.2 nF capacitor, the bias current can reach 90% of its final value within 1ms, i.e., bias current
rise-time is less than 1ms and the APC loop bandwidth is less than 30 kHz, which should be adequate for bit rates
of 155Mbps. (and all higher bit rates).
The bias generator also includes a bias current monitor mirror (BIASMON), whose output current is typically 1/100th
of the bias current. This pin can be connected directly through a resistor to ground. If this function is not needed
this pin can be left open.
3.3.3
Data Inputs
Both CML and PECL inputs signals can be AC coupled to the M02061. These inputs are internally biased to
approximately VCC3 - 1.3V. In most applications the data inputs are AC coupled with controlled impedance pcb
traces which will need to be terminated externally with a 100Ω or 150Ω resistor between the + and - inputs.
PECL and CML signals may be DC coupled to the M02061 data inputs when both the M02061 and the source of
the input signals are operating from 3.3V supplies. If the M02061 is operating from a 5V supply, PECL and CML
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Functional Description
signals may be DC coupled as long as the source of the input signals is operating at a 3.3V supply and the signals
are referenced to VCC3 at the M02061.
3.3.4
Pulse Width Adjust
The data output buffer incorporates pulse-width adjustment control to compensate for laser pulse width distortion.
A potentiometer can be connected between the PWA input and GND for adjustment (programming resistance
should be between 1kΩ and 20kΩ). By adjusting the potentiometer, the pulse-width can be adjusted over a range
of approximately ±40 ps. Pulse width control can be disabled by connecting PWA to VCC3, resulting in roughly a
50% crossing point at the output and reducing supply current by approximately 1.5mA.
3.3.5
Modulation Control
There are programmable control lines for controlling the modulation current and its temperature compensation.
These inputs can be programmed simply with a resistor to ground.
The modulation current amplitude is controlled by the MODSET input pin. The modulation current is temperature
compensated by the TCSLOPE inputs. The temperature compensation is independent of the setting.
If the temperature compensation at TCSLOPE is disabled, the modulation output current is simply:
IOUT = 100 x (1.3V / RMODSET)
Where RMODSET is the resistance from pin MODSET to ground.
Figure 3-5 is the most accurate method for selecting RTCslope.
However, you can also select RTCSLOPE using the following relationship:
RTCSLOPE = 19.5*(TC)-1.5, where TC is the desired slope of the modulation current from 25°C to 85°C in%/°C and
RTCSLOPE is in kΩ. If no temperature compensation is desired, leave RTCSLOPE open.
In any case, RTCSLOPE will have negligible effect at M02061 case temperatures below 10°C.
For example:
Given a laser with a desired modulation current at low temperatures of 30mA and a temperature coefficient of 0.5%/°C at high temperatures (which will require a laser driver temperature coefficient of +0.5%).
Choose RMODSET = 100 x (1.3V / 30mA) = 4.3kΩ
Choose RTCSLOPE =19.5*(0.5)-1.5 kΩ = 56kΩ.
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Functional Description
Figure 3-5.
TC Slope Compensation Behavior
RTCslope:
60.00
22k
27k
50.00
33k
39k
40.00
47k
% change in modulation current
51k
30.00
62k
75k
82k
20.00
100k
120k
150k
10.00
220k
390k
750k
open
0.00
-40
-20
0
20
40
60
80
100
-10.00
-20.00
-30.00
Ambient Temperature in degrees C
3.3.6
Modulator Output
The output stage is designed to drive a 25Ω output load over a wide range of currents and circuit architectures. The
laser may be AC, DC, or Differentially coupled depending on the supply voltage.
Table 3-2.
Modulation Current Maximums
VCC=5V, Laser DC coupled
Max
Modulation Current
Max Bias Current
80
60
(1)
VCC=5V, Laser AC coupled
80
(2)
VCC=3.3V, Laser DC coupled
100
VCC=3.3V, Laser AC coupled
100
60
100
100
When differentially coupling, the maximum modulation and bias current is determined by either the AC or DC coupling of the OUT+ or OUT- output,
whichever has the minimum rating.
1. When AC coupling the output should never be allowed to swing above the absolute voltage rating of the part, which is 6V.
2.
When VCC=3.3V, the OUT+ and OUT- should not be driven below 1.6V. In most 3.3V applications, this will make DC coupling impractical.
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Functional Description
When DC coupled, OUT+ should be connected through a series resistor to the laser such that the total impedance
seen at the output is 25 ohms. This will result in the optimum pulse response while allowing the maximum
modulation current (see Figure 4-2).
The output can also be AC coupled to the laser. This is the required operating mode when using a 3.3V supply
(unless the laser has a small forward voltage and OUT+ will not go below 1.6V). When AC coupled the dynamic
resistance seen by OUT+ should still be 25 ohms. In addition to a resistor in series with the laser, a capacitor is
added in series and a ferrite is used to pull up the collector at OUT+ to VCC.
When the laser is AC coupled, the OUT- pin is usually tied to the laser anode through an AC coupled series resistor
which matches the impedance seen by the OUT+ pad (see Figure 4-1).
The output stage also has a separate current path to GND labelled GND0. This isolates the output switching
currents from the rest of the system.
Figure 3-6.
Modulator Output
0.4pF
0.75 nH
*
0.75 nH
*
OUT-
OUT+
For VCC =5V, OUT+ and OUTshould not be driven below 1.15V
For VCC = 3.3V, OUT+ and OUTshould not be driven below 1.6V.
GND
A
(optional
external
inductance)
3.3.7
* Denotes bond
wire internal to
MLF package
Fail Output
The M02061 has a FAIL alarm output which is compatible with the TX_FAULT signalling requirements of common
pluggable module standards.
The ESD protection on this pin provides a true open collector output that can withstand significant variation in VCC
when signalling between circuit boards. Also, if the M02061 loses power the pull-up will signal a fail condition. In a
simple static protection scheme used by other ICs the protection diodes would clamp the FAIL signal to ground
when the chip loses power.
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Functional Description
3.3.8
TX Disable and Disable Delay Control
The DIS pin is used to disable the transmit signal (both the modulation and bias current are disabled when DIS =
high).
The DIS input is compatible with TTL levels regardless of whether VCC = 5V or VCC = 3.3V. The external 4.7kΩ
and 10kΩ pull-up resistor required by most interface standards is not needed because this pin has an internal 7kΩ
resistor to VCC.
The DISDLY pin is used in conjunction with the DIS pin to control bias current enable time. In normal operation the
DISDLY pin should be connected to ground. In this case, each time DIS transitions from high to low the bias current
will be enabled by the “slow-start” circuitry (enable time of less than 1 ms with a CAPC = 2.2 nF).
For burst mode operation a capacitor C is added to the DISDLY pin, the slow-start circuitry is disabled for
approximately T = 3 * 106 (sec/F) * C (F) following the DIS high transition (see figure 8). If the part is enabled (DIS
transitions low) during this time the bias and modulation current will quickly return to within 90% of their final value
(in less than 500ns). If DIS transitions low after the DISDLY time the slow-start circuitry will engage and the bias
current will not return to its final value for approximately 1ms (depending on the CAPC capacitor value).
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Functional Description
Figure 3-7.
DIS and DISDLY Timing
EPON Burst Mode Operation
DIS
DISDLY
IBIASOUT
OUT+
t_off BM < 500ns
t_on BM < 500ns for IMOD > 10mA
Normal Operation, (slow-start whenever part enabled)
DIS
DISDLY
t_on < 1ms, depending on CAPC
IBIASOUT
OUT+
t_off< 10μs
3.3.9
TX Disable Control
The DIS pin is used to disable the transmit signal (both the modulation and bias current are disabled when DIS =
high).
The DIS input is compatible with TTL levels regardless of whether VCC = 5V or VCC = 3.3V. The external 4.7kΩ
and 10kΩ pull-up resistor required by most interface standards is not needed because this pin has an internal 7kΩ
resistor to VCC.
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Functional Description
3.3.10
Monitor Outputs
To facilitate complying with laser safety and DDMI1 requirements, output monitors are provided for transmit power
(TxPwrMON) bias (BIASMON) and modulation current (MODMON).
These outputs will source current proportional to the emitted optical power (TxPwrMON) the bias current (BIASMON)
and modulation current (MODMON). These pins should be terminated with a resistor to ground that sets the desired
full-scale voltage (not to exceed VCC3-1V). Using a monitor polarity selection (MONPOL) these monitors can be set
to sink current instead of source current. They will then need to be terminated with a resistor to VCC3 and the
induced voltage should not exceed 2.5V.
If the outputs of these monitors are not needed, MONPOL, TxPwrMON, BIASMON, and MODMON can all be left
floating and the chip current consumption will be reduced by the value of the monitor currents.
3.4
Laser Eye Safety
Using this laser driver in the manner described herein does not ensure that the resulting laser transmitter complies
with established standards such as IEC 825. Users must take the necessary precautions to ensure that eye safety
and other applicable standards are met. Note that determining and implementing the level of fault tolerance
required by the applications that this part is going into is the responsibility of the transmitter designer and
manufacturer since the application of this device cannot be controlled by Mindspeed.
3.4.1
Safety Circuitry
On the M02061-12 with DISDLY on pin 8, SCB is internally bonded to ground so SCB is always in a logic low state.
When SCB is high the OUTP, BIASout and SVCC outputs will not be disabled when FAIL asserts (FAIL goes high).
The outputs are only disabled by making DIS high.
The FAIL output will also ignore much of the safety sensing circuitry when SCB is high. However, it will monitor the
state of the window comparators at pin APCSET. The bias current is controlled to nominally maintain the voltage at
APCSET to 1.3V. The threshold levels at the window comparators around APCSET are specified by the parameters
VBH and VBL as shown in the table below. This provides the same level of eye safety protection as our previous
generation of laser drivers. The current sourced out of pin APCSET is equal to the current into pin IPIN sourced from
the laser monitor photo diode. If the laser is emitting excess power this will be reflected in the IPIN current and the
voltage at APCSET will go high and the FAIL pin will assert. If IPIN is not connected to the laser monitor photo diode
then the voltage at APCSET will fall and FAIL will assert.
When SCB is low, safety circuitry in the M02061 will disable the modulation and bias current and assert the FAIL
output immediately upon detecting a fault condition. In addition, the supply voltage that sources the laser (SVCC or
an external switch controlled by SHDWNOUT) will immediately go open circuit and prevent any current from passing
through the laser.
Fault conditions checked by the M02061 include shorts to ground or VCC of all pins which can increase the laser
modulation or bias current.
For an initialization sequence to be successful, all the fault detection monitors must signal that the chip is “healthy”.
When DIS goes low, pins are checked for shorts to ground or VCC and a FAIL condition is latched if there is a fault.
If the state of the pins is OK, a one-shot at the reset pin begins a countdown which will latch a FAIL condition if the
bias current has not stabilized to an acceptable level during the one-shot time. The one-shot can be extended with
an external capacitor connected from the RESET pin to ground.
The one-shot1 width is approximately:
1.The one-shot is actually comprised of an oscillator and 10-bit counter.
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Functional Description
TONE-SHOT = 3 ms + (0.3 ms/pF) x (external capacitance).
Figure 3-8.
Safety Circuit Block Diagram, for SCB Pin Low
DIS
If chip is ‘healthy’, then Enable the
outputs and Start 3msec Reset
Pulse(one-shot)
AND
AND
OUTPUT_ENABLE
AND
Latch for
CrudeFaults
VccOK Detection:
SRlatch
AND
5v Mode:
Reset
:
Q
Vcc Pin
Set
_
5v Hi/Lo Limits
FAILout
(open-collector)
AND
Vcc3 Pin
Latch for
Bias_OK
Delay
3.3v Hi/Lo Limits
3.3v Mode:
ONE-SHOT:
VCC_OK
t=0
Vcc Pin
RESET
5v Hi/Lo Limits
Start
3ms + Tcap
SRlatch
Reset
:
PULSE
NOTE: Pulse stays high
if Reset pin is GNDed.
Set
_
‘1’
AND
OR
Q
optional cap for longer T_init
Vcc3 Pin
3.3v Hi/Lo Limits
CrudeFaults Detection:
OutP
Capc
MODset
> 300mV
> 300mV
> 300mV
IBout
> 300mV
BiasOK Detection:
Window Compare:
HI Limit
CrudeFaults_OK
MPCset
OR
BIAS_OK
LOW Limit
3.5
Fault Conditions when SCB is Low
This section describes the M02061 operating modes during fault conditions. Over voltage, under voltage,
pins shorted to VCC and pins shorted to ground are included in the fault table.
Table 3-3.
Circuit Response to Single-point Fault Conditions, when SCB is Low 1 2 (1 of 2)
Pin Name
VCC
DIN+, DIN-
VCC3SEL
02061-DSH-001-G
Circuit Response to Over-voltage Condition
or Short to VCC
Bias and modulation outputs are disabled once VCC rises
above the supply detection (high voltage) threshold
Circuit Response to Under-Voltage Condition
or Short to Ground
Bias and modulation outputs are disabled once VCC drops below
the supply detection (low voltage) threshold
The APC loop will attempt to compensate for the change in
The APC loop will attempt to compensate for the change in
output power. If the APC loop can not maintain the set average output power. If the APC loop can not maintain the set average
power, a fault state occurs.(1, 2)
power, a fault state occurs.(1, 2)
Does not affect laser power.
Does not affect laser power.
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Functional Description
Table 3-3.
Circuit Response to Single-point Fault Conditions, when SCB is Low 1 2 (2 of 2)
Pin Name
DIS
Circuit Response to Over-voltage Condition
or Short to VCC
Bias and modulation outputs are disabled.
3.3V operation - SVCC is opened.
Circuit Response to Under-Voltage Condition
or Short to Ground
Does not affect laser power (normal condition for circuit
operation).
5V operation - SHDWNOUT goes high.
FAIL
Does not affect laser power.
Does not affect laser power.
RESET
Does not affect laser power.
Does not affect laser power.
MODMON
Does not affect laser power.
Does not affect laser power.
BIASMON
Does not affect laser power.
Does not affect laser power.
TxPWRMON
Does not affect laser power.
Does not affect laser power.
APCSET
IPIN
IBIASOUT
(1)
A fault state occurs.(1)
A fault state occurs.(1)
A fault state occurs.(1)
The laser will be turned off, then a fault state occurs.(1)
A fault state occurs.(1)
A fault state occurs.
OUTP
Laser modulation is prevented; the APC loop will increase the A fault state occurs.(1)
bias current to compensate for the drop in laser power if it is
DC coupled. If the set output power can not be obtained, a
fault state occurs.(1, 2)
OUTN
Does not affect laser power.
Does not affect laser power.
SVCC
Does not affect laser power.
Laser bias current will be shut off and a fault state occurs.(1)
CAPC
Laser bias current will be shut off, then a fault state occurs.(1) A fault state occurs.(1)
VCC3
Bias and modulation outputs are disabled once VCC3 rises
above the supply detection (high voltage) threshold
Bias and modulation outputs are disabled once VCC3 drops
below the supply detection (low voltage) threshold
PWA
Does not affect laser power.
Does not affect laser power
Does not affect laser power. if this pin is used to control an
external switch, laser current is disabled and fault state
occurs.(1)
Does not affect laser power.
SHDWNOUT
MODSET
The APC loop will attempt to compensate for the change in
A fault state occurs.(1)
output power. If the APC loop can not maintain the set average
power, a fault state occurs.(1, 2)
TCSLOPE
Does not affect laser power.
May affect laser power. If this is the case, the APC loop will
attempt to compensate for the change in output power. If the
APC loop can not maintain the set average power, a fault state
occurs.(1, 2)
SCB
Does not affect laser power.
Does not affect laser power.
DISDLY
Does not affect laser power.
Does not affect laser power.
NOTES:
1.
A fault state will assert the FAIL output, disable bias and modulation outputs and will either open the switch at SVCC (3.3V operation) or
SHDWNOUT will go high (5V operation).
2.
Does not affect laser power when the output is AC coupled to the laser.
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4.0 Applications Information
4.1
General
•
SFP and SFF Modules
•
1G/2G/4G Fibre Channel modules
•
Short reach and Metro SONET/SDH
Figure 4-1 and Figure 4-2 illustrate typical applications for 3.3/AC coupled and 5V/DC coupled laser.
Internal
3.3V reg.
VCC
PWA
VCC 3
V CC
VCC
SHDWNOUT
Application Diagram, VCC = 3.3V Laser AC Coupled Example
V CC3
Figure 4-1.
VCC
SVCC
Internal Power Bus
OUT-
DIN +
Input
Buffer
DIN -
Output
Buffer
D - FF
Laser
Driver
OUT+
GND0
V CC
100k
VCC3 -1.3V
IBIASOUT
IPIN
Input
Buffer
VCC
(M02061-21
only)
02061-DSH-001-G
CAPC
DISDLY
TxPwrMON
BIASMON
APCSET
MODMON
Automatic Power Control
(laser bias current)
MODSET
TCSLOPE
VCC3SEL
Modulation
Control
SCB
FAIL
DIS
RESET
Safety
Circuitry with
Latched Fault
TX
Disable
VCC3
(M02061-12
only)
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Applications Information
Figure 4-2.
Application Diagram, VCC = 5V Laser DC Coupled Example
VCC
Internal
3.3V reg.
SHDWNOUT
VCC3
V CC3
PWA
VCC3
V CC
VCC=5V
SPST switch
SVCC
Internal Power Bus
OUT-
DIN +
Input
Buffer
DIN-
Output
Buffer
D - FF
Laser
Driver
OUT+
GND0
VCC3 -1.3V
IBIASOUT
IPIN
Input
Buffer
V CC
(M02061-21
only)
4.2
CAPC
DISDLY
TxPwrMON
BIASMON
APCSET
MODMON
Automatic Power Control
(laser bias current)
MODSET
TCSLOPE
Modulation
Control
VCC3SEL
SCB
FAIL
DIS
RESET
Safety
Circuitry with
Latched Fault
TX
Disable
VCC3
(M02061-12
only)
Video Operation
The M02061 can be used to transmit digital video optical data even in the presence of the pathological signal. This
is done by fully DC coupling the signal from the input to the laser output.In most data communications applications,
AC coupling occurs at 3 points in a laser driver schematic: the data inputs, the APC control, and coupling the
modulation current to the laser. In the M02061 DC coupling can be used at all 3 of these points.The data inputs can
be DC coupled using PECL or CML levels (see Section 3.3.3, “Data Inputs”). LVDS signals can be DC coupled with
level shifting.The APC of the bias current is controlled by feedback from the monitor photo diode in the laser
package in most communications applications. In video applications this monitor photo diode should not be used if
the pathological pattern may occur. Instead, the APC should be controlled in an “open loop” configuration. (Open
loop simply means a monitor photo diode is not used). In the open loop configuration the APC is controlled by a
resistor or a thermistor network or a look-up table. This removes AC time constants from the bias current. In
Figure 4-3 the BIASmon pin is connected to the APCset pin. In this case the bias current is IBIAS = 100 x (1.3V /
RAPCset). The modulation current output OUT+ can be DC coupled to the laser as shown in Figure 4-3. There are
no AC time constants in the modulation current amplitude in this configuration.
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Applications Information
Figure 4-3.
Video Application Block Diagram
VCC
Internal
3.3V reg.
SHDWNOUT
VCC3
V CC3
PWA
VCC3
V CC
VCC=5V
SPST switch
Internal Power Bus
SVCC
OUT-
DIN +
Input
Buffer
DIN-
Output
Buffer
D - FF
OUT+
Laser
Driver
GND0
VCC3 -1.3V
IBIASOUT
IPIN
Input
Buffer
V CC
(M02061-21
only)
02061-DSH-001-G
CAPC
DISDLY
TxPwrMON
BIASMON
APCSET
MODMON
Automatic Power Control
(laser bias current)
MODSET
TCSLOPE
Modulation
Control
VCC3SEL
SCB
FAIL
DIS
RESET
Safety
Circuitry with
Latched Fault
TX
Disable
VCC3
(M02061-12
only)
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5.0 Package Specification
Figure 5-1.
QFN24 Package Information
Note: View is for a 20 pin package. All dimensions in the
tables apply for the 24 pin package
02061-DSH-001-G
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General Information:
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Headquarters - Newport Beach
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Newport Beach, CA 92660
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