VITESSE
SEMICONDUCTOR CORPORATION
Preliminary Data Sheet
VSC7939
SONET/SDH 3.125Gb/s
Laser Diode Driver with Automatic Power Control
G52350-0, Rev 3.2
Page 1
02/26/01
VITESSE
SEMICONDUCTOR CORPORATION 741 Calle Plano Camarillo, CA 93012
Tel: (800) VITESSE FAX: (805) 987-5896 Email: prodinfo@vitesse.com
Internet: www.vitesse.com
Features
Applications
General Description
The VSC7939 is a single 3.3V or 5V supply laser diode driver specially designed for SONET/SDH applica-
tions up to 3.125Gb/s. External resistors set a wide range of bias and modulation currents for driving the laser.
Data and clock inputs accept differential PECL signals. The automatic power control (APC) loop maintains a
constant average optical power over temperature and lifetime. The dominant pole of the APC loop can be con-
trolled with an external capacitor. Other features include enable/disable control, short-circuit protection for the
modulation and bias inputs, short rise and fall times, programmable slow-start circuit to set laser turn-on delay,
and failure-monitor output to indicate when the APC loop is unable to maintain the average optical power. The
VSC7939 is available in die form or in a 32-pin TQFP package.
Block Diagram
Power Supply: 3.3V or 5V
5%
AC-Coupled to Laser Diode
Programmable Modulation Current: 5mA to 60mA
Programmable Bias Current: 1mA to 100mA
Enable /Disable Control
Typical Rise/Fall Times of 60ps
Automatic Optical Average Power Control
Supply Current of 33mA at 3.3V
3.3V Operation
Q
SET
CLR
Q
D
MUX
APC
BIAS
IOUT+
IOUT-
MD
MODSET
BIASMAX
CAPC
APCSET
FAIL
LATCH
1nF
MODMON
BIASMON
DATA+
DATA-
CLK+
CLK-
ENABLE
DISABLE
C
D
L
P
L
P
V
CC
V
CC
V
CC
V
CC
C
F
R
F
SONET/SDH at 622Mb/s, 1.244Gb/s,
2.488Gb/s, 3.125Gb/s
Full-Speed Fibre Channel (1.062Gb/s)
VITESSE
SEMICONDUCTOR CORPORATION
Preliminary Data Sheet
VSC7939
SONET/SDH 3.125Gb/s
Laser Diode Driver with Automatic Power Control
Page 2
G52350-0, Rev 3.2
02/26/01
VITESSE
SEMICONDUCTOR CORPORATION 741 Calle Plano Camarillo, CA 93012
Tel: (800) VITESSE FAX: (805) 987-5896 Email: prodinfo@vitesse.com
Internet: www.vitesse.com
Electrical Characteristics
Table 1: AC Specifications
AC specifications are guaranteed by design and characterization. Typical values are for 3.3V.
NOTES: (1) Measured with 622Mb/s 0-1 pattern, LATCH=high. (2) PWD = (wider pulse - narrower pulse) / 2).
Table 2: DC Specifications
Symbol
Parameter
Min
Typ
Max
Units
Conditions
t
SU
Input Latch Setup Time
100
ps
LATCH=high
t
H
Input Latch Hold Time
100
ps
LATCH=high
Enable/Start-up Delay
250
ns
t
R
Output Rise Time
60
80
ps
20% to 80%
t
F
Output Fall Time
60
80
ps
20% to 80%
PWD
Pulse Width Distortion
10
50
ps
See Notes 1, 2
CID
MAX
Maximum Consecutive Identical Digits
80
bits
t
J
Jitter Generation
7
20
ps
p-p
Jitter BW=12kHz to 20MHz,
0-1 pattern.
Symbol
Parameter
Min
Typ
Max
Units
Conditions
I
CC
Supply Current
TBD
45
mA
R
MODSET
=7.3k
R
BIASMAX
=4.8k
I
BIAS
and I
MOD
excluded
V
CC
=5V
I
BIAS
Bias Current Range
1
100
mA
Voltage at BIAS pin=(V
CC
-1.6)
I
BIAS-OFF
Bias Off Current
100
A
ENABLE=low or
DISABLE=high
(1)
S
BIAS
Bias Current Stability
230
ppm/
C
APC open loop. I
BIAS
=100mA
900
APC open loop. I
BIAS
=1mA
Bias Current Absolute Accuracy
15
%
Refers to part-to-part variation
VR
MD
Monitor Diode Reverse Bias Voltage
1.5
V
I
MD
Monitor Diode Reverse Current Range
18
1000
A
Monitor Diode Bias Setpoint Stability
-480
-50
480
ppm/
C
I
MD
=1mA
(2)
90
I
MD
=18
A
(2)
Monitor Diode Bias Absolute Accuracy
-15
15
%
Refers to part-to-part variation
I
MOD
Modulation Current Range
5
60
mA
I
MOD-OFF
Modulation Off Current
200
A
ENABLE=low or
DISABLE=high
(1)
VITESSE
SEMICONDUCTOR CORPORATION
Preliminary Data Sheet
VSC7939
SONET/SDH 3.125Gb/s
Laser Diode Driver with Automatic Power Control
G52350-0, Rev 3.2
Page 3
02/26/01
VITESSE
SEMICONDUCTOR CORPORATION 741 Calle Plano Camarillo, CA 93012
Tel: (800) VITESSE FAX: (805) 987-5896 Email: prodinfo@vitesse.com
Internet: www.vitesse.com
NOTES: (1) Both I
BIAS
and I
MOD
will turn off if any of the current set pins are grounded. (2) Assumes laser diode to monitor diode transfer func-
tion does not change with temperature.
Table 3: PECL and TTL/CMOS Inputs
and Outputs Specifications
Modulation Current Absolute Accuracy
15
%
See Note 2
Modulation Current Stability
-480
-50
480
ppm/
C
I
MOD
=60mA
250
I
MOD
=5mA
A
BIAS
BIASMON to I
BIAS
Gain
37
A/A
I
BIAS
/I
BIASMON
A
MOD
MODMON to I
MON
Gain
29
A/A
I
MOD
/I
MODMON
Symbol
Parameter
Min
Typ
Max
Units
Conditions
V
ID
Differential Input Voltage
100
1600
mV
p-p
(DATA+)-(DATA-)
V
ICM
Common-Mode Input Voltage
V
CC
-
1.49
V
CC
-
1.32
V
CC
-
V
ID
/4
V
PECL-compatible
I
IN
Clock and Data Input Current
-1
10
A
V
IH
TTL Input High Voltage
(ENABLE, LATCH)
2.0
V
V
IL
TTL Input Low Voltage
(ENABLE, LATCH)
0.8
V
TTL Output High Voltage (FAIL)
2.4
V
CC
-
0.3
V
CC
V
Sourcing 50A
TTL Output Low Voltage (FAIL)
0.1
0.44
V
Sinking 100A
Symbol
Parameter
Min
Typ
Max
Units
Conditions
VITESSE
SEMICONDUCTOR CORPORATION
Preliminary Data Sheet
VSC7939
SONET/SDH 3.125Gb/s
Laser Diode Driver with Automatic Power Control
Page 4
G52350-0, Rev 3.2
02/26/01
VITESSE
SEMICONDUCTOR CORPORATION 741 Calle Plano Camarillo, CA 93012
Tel: (800) VITESSE FAX: (805) 987-5896 Email: prodinfo@vitesse.com
Internet: www.vitesse.com
Absolute Maximum Ratings
(1)
Power Supply Voltage (V
CC
)............................................................................................................. -0.5V to +7V
Current into BIAS.....................................................................................................................-20mA to +150mA
Current into OUT+, OUT- ...............................................................................................................................TBD
Current into MD ............................................................................................................................. -5mA to +5mA
Current into FAIL ......................................................................................................................... -10mA to 30mA
Voltage at DATA+, DATA-, CLK+, CLK-, ENABLE, LATCH......................................... -0.5V to (V
CC
+ 0.5V)
Voltage at APCFILT, MODSET, BIASMAX, APCSET, MD, FAIL ............................................. -0.5V to +3.0V
Voltage at OUT+, OUT- ..................................................................................................... -0.5V to (V
CC
+ 1.5V)
Voltage at BIAS .................................................................................................................. -0.5V to (V
CC
+ 0.5V)
Continouous Power Dissipation (T
A
= +85C, TQFP derate 20.8mW/C above +85C) .......................1350mW
Operating Junction Temperature Range ...................................................................................... -55C to +150C
Storage Temperature Range ........................................................................................................ -65C to +165C
NOTE: (1) CAUTION: Stresses listed under "Absolute Maximum Ratings" may be applied to devices one at a time without caus-
ing permanent damage. Functionality at or above the values listed is not implied. Exposure to these values for extended
periods may affect device reliability.
Recommended Operating Conditions
Positive Voltage Rail (V
CC
)..................................................................................................... +3.135V to +5.25V
Negative Voltage Rail (GND) ............................................................................................................................0V
Modulation Current (I
MOD
)
(1)
.......................................................................................................................30mA
Ambient Temperature Range (T
A
)................................................................................................. -40C to +85C
NOTE:
(1) V
CC
= 3.3V, I
BIAS
= 60mA.
VITESSE
SEMICONDUCTOR CORPORATION
Preliminary Data Sheet
VSC7939
SONET/SDH 3.125Gb/s
Laser Diode Driver with Automatic Power Control
G52350-0, Rev 3.2
Page 5
02/26/01
VITESSE
SEMICONDUCTOR CORPORATION 741 Calle Plano Camarillo, CA 93012
Tel: (800) VITESSE FAX: (805) 987-5896 Email: prodinfo@vitesse.com
Internet: www.vitesse.com
Bare Die Pad Descriptions
Figure 1: Pad Assignments
VSC7939
Pad 10
CLK-
Pad 9
CLK+
Pad 8
VCC1
Pad 7
GND1
Pad 6
VCC1
Pad 5
DATA-
Pad 4
DATA+
Pad 3
VCC1
Pad 2
GND1
Pad 1
GND2
Pad 48
VCC2
Pad 47
BIASMAX
20m
(0.0008")
1773m (0.0698")
(Pin 1)
(Pin 2)
(Pin 3)
(Pin 4)
(Pin 5)
(Pin 6)
(Pin 18)
(Pin 19)
(Pin 20)
(Pin 21)
(Pin 22)
(Pin 23)
(Pin 24)
(Pin 25)
(Pin 26)
(Pin 27)
(Pin 28)
(Pin 29)
(Pin 31)
(Pin 30)
(Pin 32)
(Pin 7)
(Pin 8)
(Pin 9)
(Pin 10)
(Pin 11)
(Pin 12)
(Pin 13)
(Pin 14)
(Pin 15)
(Pin 16)
(Pin 17)
Pad 46
MODSET
Pad 45
GND2
Pad 44
APCSET
Pad 43
RESERVED
Pad 42
GND3
Pad 41
PB_GND
Pad 40
GND3
Pad 39
PB_GND
Pad 38
CAPC
Pad 37
VCC3
Pad 36
GND3
Pad 12
GND1
Pad 13
LATCH
Pad 14
ENABLE
Pad 15
DISABLE
Pad 16
GND1
Pad 17
BIASMON
Pad 18
MODMON
Pad 19
FAIL
Pad 20
GND4
Pad 21
PB_GND
Pad 22
APCFILT
Pad 23
GND4
Pad 24
VCC4
Pad 25
BIAS
Pad 11
VCC1
Pad 27
VCC4
Pad 28
DB_OUT+
Pad 29
OUT+
Pad 30
OUT-
Pad 31
DB_OUT-
Pad 32
VCC4
Pad 33
GND4
Pad 34
GND3
Pad 35
MD
Pad 26
PB_GND1
Die Size:
1773m x 2233m (0.0698" x 0.0879")
Die Thickness:
625
m (0.0246
"
)
Pad Pitch:
115
m (0.0045
"
)
Pad Size:
95m x 95m (0.0037
"
x 0.0037
"
)
Pad to Pad Clearance:
20m (0.0008
"
)
Pad Passivation Opening:
95m x 95m (0.0037
"
x 0.0037
"
)
Scribe Size:
75m (0.0030
"
)
2233m
(0.0879")
75m
(0.0030")
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