19-2934; Rev 1; 6/07
10Gbps Modulator Driver
General Description
The MAX3942 is designed to drive high-speed optical
modulators at data rates up to 10.7Gbps. It functions as
a modulation circuit, with an integrated control op amp
externally programmed by a DC voltage.
A high-bandwidth, fully differential signal path is inter-
nally implemented to minimize jitter accumulation. When
a clock signal is available, the integrated data-retiming
function can be selected to reject input-signal jitter.
The MAX3942 receives differential CML signals (ground-
referenced) with on-chip line terminations of 50Ω. Each
of the differential outputs has an on-chip 50Ω resistor for
back termination. The driver is able to deliver a modula-
tion current of 40mA
P-P
to 120mA
P-P
, with an edge
speed of 23ps (typical 20% to 80%). This modulation
current reflects a modulation voltage of 1.0V
P-P
to 3.0V
P-
P
single ended or 2.0V
P-P
to 6.0V
P-P
differential.
The MAX3942 also includes an adjustable pulse-width
control circuit to precompensate for asymmetrical mod-
ulator characteristics. It is available in a compact 4mm
✕
4mm, 24-pin thin QFN package and operates over
the -40°C to +85°C temperature range.
♦
23ps Edge Speed
♦
Single-Ended Modulation Voltage Up to 3V
P-P
♦
Differential Modulation Voltage Up to 6V
P-P
♦
Selectable Data-Retiming Latch
♦
Up to 10.7Gbps Operation
♦
50Ω On-Chip Input and Output Terminations
♦
Pulse-Width Adjustment
♦
Enable and Polarity Controls
♦
ESD Protection
Features
MAX3942
Applications
Mach Zehnder Modulators
Packaged Direct-Modulated Lasers
SONET OC-192 and SDH STM-64 Transmission
Systems
DWDM Systems
Long/Short-Reach Optical Transmitters
10Gbps Ethernet
Ordering Information
PART
MAX3942ETG
TEMP RANGE PIN-PACKAGE
-40°C to +85°C 24 Thin QFN (4mm
4mm)
4mm)
MAX3942ETG+ -40°C to +85°C 24 Thin QFN (4mm
Pin Configuration appears at end of data sheet.
+Denotes
a lead-free package.
Typical Application Circuit
-5.2V
50Ω
L2
0.01μF
DATA+
0.01μF
50Ω
DATA+
PLRT
MODEN
RTEN
GND
OUT-
0.01μF
50Ω
MACH ZEHNDER
MODULATOR
50Ω
10Gbps
SERIALIZER
CLK+
0.01μF
CLK-
50Ω
CLK-
PWC+
2kΩ
PWC-
MODSET
+
V
MODSET
-
-5.2V
1000pF
0.1μF
OUT+
V
EE
0.01μF
50Ω
CLK+
MAX3952
DATA-
50Ω
DATA-
MAX3942
L1
0.01μF
50Ω
-5.2V
-5.2V
L1 AND L2 ARE HIGH-FREQUENCY FERRITE BEADS
REPRESENTS A CONTROLLED-IMPEDANCE TRANSMISSION LINE.
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
10Gbps Modulator Driver
MAX3942
ABSOLUTE MAXIMUM RATINGS
Supply Voltage V
EE
..............................................-6.0V to +0.5V
Voltage at
MODEN,
RTEN,
PLRT, MODSET............................(V
EE
- 0.5V) to +0.5V
Voltage at DATA+, DATA-, CLK+, and CLK-……-1.65V to +0.5V
Voltage at OUT+, OUT- ................................……….-4V to +0.5V
Voltage at PWC+, PWC- ...................(V
EE
- 0.5V) to (V
EE
+ 1.7V)
Continuous Power Dissipation (T
A
= +85°C)
24-Pin Thin QFN (derate 20.8mW/° above +85°C) ....1354mW
Current into or out of OUT+, OUT-.................……………...80mA
Storage Temperature Range .....................……-55°C to +150°C
Operating Temperature Range ....................……-40°C to +85°C
Lead Temperature (soldering, 10s)............………………+300°C
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
(V
EE
= -5.5V to -4.9V, T
A
= -40°C to +85°C. Typical values are at V
EE
= -5.2V, I
MOD
= 100mA, and T
A
= +25°C, unless otherwise noted.)
PARAMETER
Power-Supply Voltage
Supply Current
Power-Supply Noise Rejection
SIGNAL INPUT
(Note 3)
Input Data Rates
Single-Ended Input Resistance
Single-Ended Input Voltage
Differential Input Voltage
Differential Input Return Loss
MODULATION
(Note 5)
Maximum Modulation Current
Minimum Modulation Current
MODSET Voltage Range
Equivalent Modulation
Modulation Set Bandwidth
MODSET Input Resistance
Modulation-Current
Temperature Stability
Modulation-Current-Setting Error
Output Resistance
R
OUT
(Note 6)
50
driver load, T
A
= +25°C
OUT+ and OUT- to GND
-980
-10
42.5
50
V
MODSET
R
MODEQV
(Note 7)
Modulation depth 10%, 50
driver load
V
MODSET
= V
EE
V
EE
11.1
5
20
0
+10
58.5
MHz
k
ppm/°C
%
112
120
37
41
V
EE
+
mA
P-P
mA
P-P
V
R
IN
V
IS
V
ID
RL
IN
NRZ
Input to GND
DC-coupled, Figure 1a
AC-coupled, Figure 1b
DC-coupled (Note 4)
AC-coupled (Note 4)
15GHz
42.5
-1
-0.4
0.2
0.2
15
10.7
50
58.5
0
+0.4
2.0
1.6
V
V
P-P
dB
Gbps
SYMBOL
V
EE
I
EE
PSNR
Excluding I
MOD
(Note 1)
f
Retime disabled
Retime enabled
CONDITIONS
MIN
-5.5
125
140
15
TYP
MAX
-4.9
175
200
UNITS
V
mA
dB
2MHz (Note 2); see Figure 3
2
_______________________________________________________________________________________
10Gbps Modulator Driver
ELECTRICAL CHARACTERISTICS (continued)
(V
EE
= -5.5V to -4.9V, T
A
= -40°C to +85°C. Typical values are at V
EE
= -5.2V, I
MOD
= 100mA, and T
A
= +25°C, unless otherwise noted.)
PARAMETER
Off Current
Differential Output Return Loss
Output Edge Speed
Setup/Hold Time
Pulse-Width Adjustment Range
Pulse-Width Control Input
Range (Single Ended)
Pulse-Width Control Input
Range (Differential)
Output Overshoot
Driver Random Jitter
Driver Deterministic Jitter
CONTROL INPUTS
Input High Voltage
Input Low Voltage
Input Current
V
IH
V
IL
(Note 10)
(Note 10)
(Note 10)
-80
V
EE
+
2.0
V
EE
+
0.8
+200
V
V
μA
RJ
DR
DJ
DR
t
SU
, t
HD
RL
OUT
SYMBOL
CONDITIONS
MODEN
= V
EE
, MODSET = V
EE
, DATA+ =
high, DATA- = low
I
MOD
= 50mA
Figure 2 (Note 6)
(Notes 6, 8)
For PWC+ and PWC-
(PWC+) - (PWC-)
(Notes 6, 8)
(Note 6)
PWC- = GND (Notes 6, 9)
10GHz
25
±30
V
EE
+
0.5
-0.5
5
0.3
8
0.8
13
±50
V
EE
+
1.5
+0.5
10
23
32
20% to 80% (Notes 6, 8)
MIN
TYP
MAX
1.6
UNITS
mA
dB
ps
ps
ps
V
V
%
ps
RMS
ps
P-P
MAX3942
Note 1:
Supply current remains elevated once the retiming function has been enabled. Power must be cycled to reduce supply
current after the retiming function has been disabled.
Note 2:
Power-supply noise rejection is specified as PSNR = 20Log(V
noise (on Vcc)
/
ΔV
OUT
). V
OUT
is the voltage across a 50Ω load.
V
noise (on Vcc)
= 100mV
P-P
.
Note 3:
For DATA+, DATA-, CLK+, and CLK-.
Note 4:
CLK input characterized at 10.7Gbps.
Note 5:
Minimum voltage on OUT+ and OUT- is V
EE
+ 1.9V.
Note 6:
Guaranteed by design and characterization using the circuit shown in Figure 3.
Note 7:
R
MODEQV
= (V
MODSET
- V
EE
) / (I
MOD
- 37mA).
Note 8:
50Ω load, characterized at 10.7Gbps with a 1111 1111 0000 0000 pattern.
Note 9:
Deterministic jitter is defined as the arithmetic sum of PWD (pulse-width distortion) and PDJ (pattern-dependent jitter).
Measured with a 10.7Gbps 2
7
- 1 PRBS pattern with 80 zeros and 80 ones inserted in the data pattern.
Note 10:
For
MODEN
and PLRT.
_______________________________________________________________________________________
3
10Gbps Modulator Driver
MAX3942
Test Circuits and Timing Diagrams
0V
100mV
1.0V
-0.5V
-1.0V
(a) DC-COUPLED SINGLE-ENDED CML INPUT
0.4V
800mV
0V
100mV
-0.4V
(b) AC-COUPLED SINGLE-ENDED (CML OR PECL) INPUT
Figure 1. Definition of Single-Ended Input Voltage Range
CLK+
CLK-
t
SU
DATA-
t
HD
V
IS
= 0.1V
P-P
TO 1V
P-P
DC-COUPLED
0.1V
P-P
TO 0.8V
P-P
AC-COUPLED
DATA+
(DATA+) - (DATA-)
V
ID
= 0.2V
P-P
TO 2V
P-P
DC-COUPLED
0.2V
P-P
TO 1.6V
P-P
AC-COUPLED
I
OUT+
I
MOD
= 40mA
P-P
TO 120mA
P-P
I
OUT-
NOTE:
I
OUT+
AND I
OUT-
RELATE TO RETIMED DATA. SEE FIGURE 3 FOR POLARITY.
Figure 2. Setup and Hold Timing Definition
4
_______________________________________________________________________________________
10Gbps Modulator Driver
Test Circuits and Timing Diagrams (continued)
MAX3942
PLRT
50Ω
50Ω
PATTERN
GENERATOR
50Ω
50Ω
DATA+
DATA-
V
EE
CLK+
RTEN
MODEN
PWC+
PWC-
I
OUT-
CLK-
OSCILLOSCOPE
OUT-
50Ω
MAX3942
OUT+
I
OUT+
50Ω
50Ω
Z
L
MODSET
GND
-5.2V
0.1μF
1000pF
V
MODSET
V
EE
Figure 3. AC Characterization Circuit
_______________________________________________________________________________________
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