MAX3863ETJ+T [MAXIM]
Interface Circuit, BIPolar, ROHS COMPLIANT, TQFN-32;
| 型号： | MAX3863ETJ+T |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Interface Circuit, BIPolar, ROHS COMPLIANT, TQFN-32 接口集成电路 |
| 文件： | 总15页 (文件大小：400K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-2281; Rev 4; 11/08
2.7Gbps Laser Driver with Modulation
Compensation
MAX863
General Description
Features
♦ Single +3.3V Power Supply
♦ 58mA Power-Supply Current
♦ Up to 2.7Gbps (NRZ) Operation
♦ On-Chip Termination Resistors
♦ Automatic Power Control (APC)
The MAX3863 is designed for direct modulation of laser
diodes at data rates up to 2.7Gbps. An automatic
power-control (APC) loop is incorporated to maintain a
constant average optical power. Modulation compensa-
tion is available to increase the modulation current in
proportion to the bias current. The optical extinction
ratio is then maintained over temperature and lifetime.
♦ Compensation for Constant Extinction Ratio
♦ Programmable Modulation Current Up to 80mA
♦ Programmable Bias Current Up to 100mA
♦ 50ps Typical Rise/Fall Time
♦ Pulse-Width Adjustment Circuit
♦ Selectable Data-Retiming Latch
♦ Failure Detector
The laser driver can modulate laser diodes at ampli-
tudes up to 80mA. Typical (20% to 80%) edge speeds
are 50ps. The MAX3863 can supply a bias current up
to 100mA. External resistors can set the laser output
levels.
The MAX3863 includes adjustable pulse-width control
to minimize laser pulse-width distortion. The device
offers a failure monitor output to indicate when the APC
loop is unable to maintain the average optical power.
♦ Mark-Density Monitor
♦ Current Monitors
♦ ESD Protection
The MAX3863 accepts differential CML clock and data
input signals with on-chip 50Ω termination resistors. If a
clock signal is available, an input data-retiming latch
can be used to reject input pattern-dependent jitter.
The laser driver is fabricated with Maxim’s in-house
second-generation SiGe process.
Ordering Information
PART
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
32 TQFN-EP*
32 QFN-EP*
MAX3863ETJ+
MAX3863EGJ
+Denotes a lead-free/RoHS-compliant package.
*EP = Exposed pad.
Pin Configuration
Applications
SONET and SDH Transmission Systems
WDM Transmission Systems
3.2Gbps Data Communications
Add/Drop Multiplexers
TOP VIEW
V
1
2
3
4
5
6
7
8
24 MDMON
23 MD
CC
Digital Cross-Connects
DATA+
DATA-
Section Regenerators
22
V
CC
Long-Reach Optical Transmitters
V
V
21 MODN
20 MOD
CC
CC
MAX3863
CLK+
CLK-
19
V
CC
18 BIAS
V
FAIL
17
CC
*EP
TQFN-EP
QFN-EP
*THE EXPOSED PAD MUST BE SOLDERED TO GND ON THE CIRCUIT BOARD.
________________________________________________________________ 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.
2.7Gbps Laser Driver with Modulation
Compensation
ABSOLUTE MAXIMUM RATINGS
Supply Voltage V ...............................................-0.5V to +5.0V
BIAS Current ...................................................-20mA to +150mA
MD Current............................................................-5mA to +5mA
Operating Junction Temperature Range...........-55°C to +150°C
Storage Temperature Range.............................-55°C to +150°C
CC
DATA+, DATA- and CLK+, CLK- ....(V
- 1.5V) to (V + 0.5V)
CC
CC
RTEN, EN, BIAS, MK+, MK-, PWC+, PWC-
MODMON, BIASMON, MDMON, MODCOMP,
APCFILT1, APCFILT2, BIASMAX, MODSET,
APCSET Voltage ......................................-0.5V to (V
MOD, MODN Voltage .......................................0 to (V
Continuous Power Dissipation (T = +85°C)
A
+ 0.5V)
+ 1.5V)
32-Pin QFN, TQFN (derate 21.2mW/°C above +85°C)....1.3W
Processing Temperature (die) .........................................+400°C
Lead Temperature (soldering, 10s) ................................ +300°C
CC
CC
MOD, MODN Current......................................-20mA to +150mA
MAX863
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
CC
= +3.15V to +3.6V, T = -40°C to +85°C. Typical values are at V
= +3.3V, I
= 50mA, I = 40mA, T = +25°C, unless
MOD A
A
CC
BIAS
otherwise noted.) (Notes 1, 9)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
58
MAX
UNITS
mA
dB
Power-Supply Current
I
(Note 2)
85
CC
Power-Supply Noise Rejection
Power-Supply Threshold
Single-Ended Input Resistance
Bias-Current Setting Range
PSNR
f = 100kHz, 100mV
Output enabled
(Note 10)
40
P-P
2.8
50
V
Input to V
40
4
60
100
+15
+20
0.1
Ω
CC
mA
APC open loop, I
APC open loop, I
EN high
= 100mA, T = +25°C
-15
-20
BIAS
A
Bias-Current Setting Error
%
= 4mA, T = +25°C
BIAS
A
Bias Off-Current
mA
I
to I
Ratio
BIASMON
34
40
46
mA/mA
BIAS
APC open loop, 10mA ≤ I
≤ 100mA (Note 3) -480
+480
BIAS
Bias-Current Temperature Stability
ppm/°C
APC open loop, 4mA ≤ I
≤ 100mA (Note 3)
390
BIAS
Modulation-Current Setting Range
Modulation-Current Setting Error
Modulation Off-Current
7
80
+15
0.1
mA
%
APC open loop, 25Ω load, T = +25°C
-15
A
EN high
mA
Modulation-Current Temperature
Stability
APC open loop (Note 3)
-480
+480 ppm/°C
I
to I
Ratio
MODMON
38
0
46
53
1.5
mA/mA
mA/mA
V
MOD
Modulation Compensation Range
MD Pin Voltage
K
K = ΔI
/ΔI
MODC BIAS
1.75
Monitor Photodiode Current
Range
I
30
1
2000
1000
µA
MD
APC Loop Time Constant
APC Open Loop
t
(Notes 3, 4)
4mA ≤ I
4
µs
APC
≤ 10mA (Note 3)
390
1.0
mA
BIAS
V
to I
Ratio
R = 4kΩ
MDMON
0.8
2.0
1.2
0.8
0.4
mV/µA
MDMON
MD
EN and RTEN Input High
EN and RTEN Input Low
FAIL Output High
V
V
V
V
V
IH
V
IL
V
Source 150µA
Sink 2mA
2.4
OH
FAIL Output Low
V
OL
2
_______________________________________________________________________________________
2.7Gbps Laser Driver with Modulation
Compensation
MAX863
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +3.15V to +3.6V, T = -40°C to +85°C. Typical values are at V
= +3.3V, I
= 50mA, I = 40mA, T = +25°C, unless
MOD A
A
CC
BIAS
otherwise noted.) (Notes 1, 9)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX UNITS
At high
At low
V
CC
Single-Ended Input (DC-Coupled)
Single-Ended Input (AC-Coupled)
V
V
IS
IS
ID
V
- 1.0
V
- 0.1
CC
CC
V
+
V
+
-
CC
CC
0.4
At high
At low
0.05
V
V
V
-
V
CC
CC
0.4
0.05
DC-coupled
AC-coupled
NRZ (Note 3)
0.2
0.2
2.0
1.6
Differential Input Swing
Input Data Rate
V
V
P-P
3.2
17
14
Gbps
dB
f ≤ 2.7GHz
2.7GHz < f ≤ 4GHz
Input Return Loss
RL
(Notes 3, 5)
IN
Turn-Off Delay from EN
Setup Time
EN = high (Note 3)
Figure 2 (Note 3)
Figure 2 (Note 3)
1.0
µs
ps
ps
ps
ps
t
90
SU
Hold Time
t
90
HD
Pulse-Width Adjustment Range
Pulse-Width Stability
Z = 25Ω (Notes 3, 6)
L
185
220
PWC+ and PWC- open (Notes 3, 6)
18.5
1.0
Differential Pulse-Width Control
Input Range
For PWC+ and PWC- (Notes 3, 7), V = 0.5V
-1.0
V
V
CM
Differential Mark Density
0% to 100%, V + - V
-
MK
0.85
MK
Differential Mark-Density Voltage
to Mark-Density Ratio
15.5
V/%
Output Edge Speed
Output Overshoot
Random Jitter
t , t
R
Z = 25Ω (20% to 80%) (Notes 3, 6)
50
7
85
ps
%
F
L
δ
Z = 25Ω (Note 3)
L
(Notes 3, 6)
0.8
8
1.3
40
40
ps
RMS
Data Rate = 2.7Gbps (Notes 3, 8)
Data Rate = 3.2Gbps (Notes 3, 8)
Deterministic Jitter
ps
P-P
10
Note 1: Specifications at -40°C are guaranteed by design and characterization.
Note 2: Excluding I , I , I , I , I , and I . Input clock and data are AC-coupled.
BIAS MOD BIASMON MODMON FAIL
PWC
Note 3: Guaranteed by design and characterization.
Note 4: An external capacitor at APCFILT1 and APCFILT2 is used to set the time constant.
Note 5: For both data inputs DATA+, DATA- and clock inputs CLK+, CLK-.
Note 6: Measured using a 2.7Gbps repeating 0000 0000 1111 1111 pattern.
Note 7: For pulse width, PW = 100%: Rp = Rn = 500Ω (or open) or PWC+ = PWC- ≈ +0.5V. For PW > 100%: Rp > Rn or PWC+ >
PWC-. For PW < 100%: Rp < Rn or PWC+ < PWC-.
Note 8: Measured using a 213 - 1 PRBS with 80 zeros + 80 ones input data pattern or equivalent.
Note 9: AC characterization performed using the circuit in Figure 1.
Note 10: Power-Supply Noise Rejection (PSNR) = 20log (V
/ΔV
). V
is the voltage across the 25Ω load when no
10 NOISE (on VCC)
OUT
OUT
input is applied.
_______________________________________________________________________________________
3
2.7Gbps Laser Driver with Modulation
Compensation
Typical Operating Characteristics
(T = +25°C, unless otherwise noted. See Typical Operating Circuit.)
A
ELECTRICAL EYE DIAGRAM
ELECTRICAL EYE DIAGRAM
ELECTRICAL EYE DIAGRAM
(I
MOD
= 80mA, DATA RATE = 2.7Gbps,
(I
MOD
= 80mA, DATA RATE = 3.2Gbps,
(I
= 7mA, DATA RATE = 2.7Gbps,
MOD
13
13
13
PATTERN 2 - 1 + 80CID)
PATTERN 2 - 1 + 80CID)
PATTERN 2 - 1 + 80CID)
MAX863
52ps/div
52ps/div
52ps/div
ELECTRICAL EYE DIAGRAM
OPTICAL EYE DIAGRAM
OPTICAL EYE DIAGRAM
(I
= 7mA, DATA RATE = 3.2Gbps,
(I
= 40mA, DATA RATE = 2.5Gbps,
(I
= 40mA, DATA RATE = 3.2Gbps,
MOD
MOD
MOD
13
13
13
PATTERN 2 - 1 + 80CID)
PATTERN 2 - 1 + 80CID)
PATTERN 2 - 1 + 80CID)
52ps/div
58ps/div
58ps/div
SUPPLY CURRENT (I ) vs.TEMPERATURE
CC
(EXCLUDES BIAS AND
MODULATION CURRENTS)
PULSE-WIDTH ADJUST
DETERMINISTIC JITTER vs. I
MOD
vs. DIFFERENTIAL V
PWC
16
14
12
10
8
80
75
70
65
60
55
50
45
40
300
200
100
0
3.2Gbps
2.7Gbps
6
-100
-200
-300
4
2
0
5
15 25 35 45 55 65 75 85
-40
-20
0
20
40
60
80
-0.8 -0.6 -0.4 -0.2
V
0
0.2 0.4 0.6 0.8
(V)
PWC-
I
(mA)
TEMPERATURE (°C)
- V
MOD
PWC+
4
_______________________________________________________________________________________
2.7Gbps Laser Driver with Modulation
Compensation
MAX863
Typical Operating Characteristics (continued)
(T = +25°C, unless otherwise noted. See Typical Operating Circuit.)
A
MODULATION CURRENT vs.
MODULATION SET RESISTOR
BIAS CURRENT
vs. BIASMAX SET RESISTOR
MODULATION MONITOR VOLTAGE
vs. MODULATION CURRENT
100
10
1
1000
200
180
160
140
120
100
80
100
10
60
40
20
0
1
0.1
1
10
100
0.1
1
10
(kΩ)
100
5
20
35
I
50
(mA)
65
80
R
(kΩ)
R
BIASMAX
MODSET
MOD
BIAS MONITOR VOLTAGE
vs. BIAS CURRENT
MONITOR DIODE CURRENT
vs. APCSET RESISTOR
DIODE-CURRENT MONITOR VOLTAGE
vs. MONITOR DIODE CURRENT
10
3.0
2.5
2.0
1.5
1.0
0.5
0
300
250
200
150
100
50
1
0.1
0.01
0
0.1
10
100
1000
0
0.5
1.0
I
1.5
(mA)
2.0
2.5
0
10 20 30 40 50 60 70 80 90 100
(mA)
1
R
(kΩ)
I
APCSET
MD
BIAS
COMPENSATION (K)
POWER-SUPPLY NOISE REJECTION
vs. FREQUENCY
vs. R
MODCOMP
SINGLE-ENDED S11 vs. FREQUENCY
10
1
120
100
80
60
40
20
0
0
-5
-10
-15
-20
-25
-30
-35
-40
0.1
0.01
0.01
0.1
1
10
100
0.1
1
10
100
1000 10,000
0
1
2
3
4
5
R
(kΩ)
FREQUENCY (kHz)
FREQUENCY (GHz)
MODCOMP
_______________________________________________________________________________________
5
2.7Gbps Laser Driver with Modulation
Compensation
Pin Description
PIN
NAME
FUNCTION
1, 4, 5, 8,
14, 19, 22, 27
V
CC
Positive Supply Voltage
2
3
6
7
9
DATA+
DATA-
CLK+
Data Input, with On-Chip Termination
Complementary Data Input, with On-Chip Termination
Clock Input for Data Retiming, with On-Chip Termination
MAX863
CLK-
Complementary Clock Input for Data Retiming, with On-Chip Termination
Monitor Diode Current Set Point
APCSET
APC Loop Filter Capacitor. Short to ground to disable the correction loop through the monitor
diode.
10
APCFILT1
11
12
APCFILT2
PWC+
APC Loop Filter Capacitor
Input for Modulation Pulse-Width Adjustment. Connected to GND through R
.
PWC
Complementary Input for Modulation Pulse-Width Adjustment. Connected to GND through
13
PWC-
R
.
PWC
15
16
17
MK+
MK-
Voltage Proportional to the Mark Density. MK+ = MK- for 50% duty cycle.
Voltage Inversely Proportional to the Mark Density
FAIL
Alarm for Shorts on Current Set Pins and APC Loop Failure Conditions, Active Low
Laser Diode Bias Current Source (Sink Type) to Bias the Laser Diode. Connect to the laser
with an inductor.
18
BIAS
20
21
23
MOD
MODN
MD
Driver Output. AC-coupled to the laser diode.
Complementary Driver Output. Connect to dummy load off-chip.
Monitor Diode Connection
Monitor for MD Current. Voltage developed across an external resistor from mirrored MD
current.
24
MDMON
Monitor for Modulation Current. Voltage developed from I
resistor.
mirrored through an external
MOD
25
26
28
MODMON
BIASMON
MODCOMP
Monitor for Bias Current. Voltage developed from I
mirrored through an external resistor.
BIAS
Couples the Bias Current to the Modulation Current. Mirrors I
Open for zero coupling.
through an external resistor.
BIAS
29
30
31
32
MODSET
BIASMAX
EN
External Resistor to Program I
(I
= I
+ I
)
MODC MOD
MODS
MODC
External Resistor to Program the Maximum I
BIAS
Modulation and Bias Current Enable, Active Low. Current disabled when floating or high.
Data Retiming Enable Input, Active Low. Retiming disabled when floating or high.
RTEN
Exposed Pad. The exposed pad must be soldered to circuit-board ground for proper thermal
and electrical operation.
EP
—
6
_______________________________________________________________________________________
2.7Gbps Laser Driver with Modulation
Compensation
MAX863
V
CC
A - TOKO FSLB2520-330K
B - MURATA BLM11HA601SPT
A
B
A
B
V
V
CC
CC
50Ω
50Ω
DATA+
DATA-
DATA+
DATA-
25Ω
MODN
0.1μF
V
OSCILLOSCOPE
CC
MAX3863
V
CC
50Ω
MOD
0.1μF
APCFILT1
50Ω
50Ω
CLK+
CLK-
CLK+
CLK-
50Ω
50Ω
V
CC
BIAS
EN
RTEN
15Ω
Figure 1. AC Characterization
Mark-Density Outputs
Detailed Description
The MK+ and MK- outputs monitor the input signal
mark density. With a 50% mark density, both outputs
are the same voltage. More ones cause the MK+ volt-
age to increase and the MK- voltage to decrease.
Fewer ones than zeros cause MK- to be at a higher
voltage than MK+.
The MAX3863 laser driver has two main components: a
high-speed modulation driver and a biasing block with
APC. The clock and data inputs to the modulation driver
use CML logic levels. The optional clock signal synchro-
nizes data transitions for minimum pattern-dependent jit-
ter. Outputs to the laser diode consist of a switched
modulation current and a steady bias current. The APC
loop adjusts the laser diode bias current to maintain con-
stant average optical power. Compensation of the modu-
lation current can be programmed to keep a constant
extinction ratio over time and temperature. The modula-
tion output stage uses a programmable current source
with a maximum current of 80mA. A high-speed differen-
tial pair switches the source to the laser diode. The rise
and fall times are typically 50ps.
Pulse-Width Control
A pulse-width adjustment range of 50% to 150%
( 185ps) is available at 2.7Gbps. This feature compen-
sates pulse-width distortion elsewhere in the system.
Resistors at the PWC+ and PWC- pins program the
pulse width. The sum of the resistors is 1kΩ. The pins
can be left open for a 100% pulse width. A voltage also
can control these pins. A differential voltage of 600mV
(typ) gives 185ps of pulse-width distortion.
Optional Input Data Retiming
To eliminate pattern-dependent jitter in the input data, a
synchronous differential clock signal should be con-
nected to the CLK+ and CLK- inputs, and the RTEN
control input should be connected low. The input data
is retimed on the rising edge of CLK+. If RTEN is tied
high or is left floating, the retiming function is disabled,
and the input data is directly connected to the output
stage. Leave CLK+ and CLK- open when retiming is
disabled.
Output Enable
The MAX3863 incorporates an input to enable current
to the laser diode. When EN is low, the modulation and
bias outputs at the MOD pin are enabled. When EN is
high or floating, the output is disabled. In the disabled
condition, bias and modulation currents are off.
Power-Supply Threshold
To prevent data errors caused by low supply, the
MAX3863 disables the laser diode current for supply
voltage less than 2.7V. The power-supply threshold and
_______________________________________________________________________________________
7
2.7Gbps Laser Driver with Modulation
Compensation
the output-enable must be true to enable bias and
modulation currents.
voltage to monitor diode current, use an external 4kΩ
resistor at the MDMON output. Resistors for BIASMON
and MODMON are 100Ω. The minimum voltage at the
BIASMON and MODMON must be 2.1V for compliance.
APC Loop Enable
The APC loop is enabled when an external capacitor is
placed between the APCFILT1 and APCFILT2 pins.
This capacitor sets the time constant of the APC loop.
To open the APC loop, the APCFILT1 pin is shorted to
ground. This shorts the feedback from the monitor
diode and causes the bias current to rise to the maxi-
mum value set by the BIASMAX pin.
I
BIAS
40
V
= V
−
−
×100Ω
×100Ω
BIASMON
CC
I
MAX863
MOD
45
V
= V
CC
MODMON
APC Filter
The APC loop keeps the average optical power from the
laser constant. An external filter capacitor is used to stabi-
lize the APC loop. The typical capacitor value is 0.01µF.
I
MD
4
V
=
× 4kΩ
MDMON
Design Procedure
APC Failure Monitor
The MAX3863 provides an APC failure monitor
(TTL/CMOS) to indicate an APC loop tracking failure.
FAIL is set low when the APC loop cannot adjust the
bias current to maintain the desired monitor current.
When designing a laser transmitter, the optical output is
usually expressed in terms of average power and
extinction ratio. Table 1 shows relationships helpful in
converting between the optical average power and the
modulation current. These relationships are valid only if
the mark density and duty cycle of the optical wave-
form are 50%.
Short-Circuit Protection
The MAX3863 provides short-circuit protection for mod-
ulation, bias, and monitor current sources. If BIASMAX,
MODSET, or APCSET is shorted to ground, the bias
and modulation output are turned off and FAIL is active.
For a desired laser average optical power (P
) and
AVG
optical extinction ratio (r ), the required modulation cur-
e
rent can be calculated based on the laser slope effi-
ciency (η) using the equations in Table 1.
Current Monitors
The MAX3863 features monitor outputs for bias current
(BIASMON), modulation current (MODMON), and moni-
tor diode current (MDMON). The monitors are realized
by mirroring a fraction of the current and developing a
voltage across an external resistor. For the specified
Laser Current Compensation
Requirements
Determine static bias and modulation current require-
ments from the laser threshold current and slope efficien-
cy. To use the APC loop with modulation compensation,
CLK+
CLK-
V
= 0.1V TO 0.8V
= 0.1V TO 0.8V
IS
IS
t
t
HD
SU
DATA-
DATA+
V
(DATA+) - (DATA-)
V
ID
= 0.2V TO 1.6V
P-P P-P
I
7mA TO 80mA
MOD
Figure 2. Required Input Signal, Setup/Hold-Time Definition and Output Polarity
_______________________________________________________________________________________
8
2.7Gbps Laser Driver with Modulation
Compensation
MAX863
the current from the inductor flows to the bias input.
Table 1. Optical Power Relations
This reduces the current through the laser diode from
PARAMETER
Average Power
SYMBOL
RELATION
the average of I
by half of I
. The resulting
MOD
BIAS
P
P
= (P + P )/2
peak-to-peak current through the laser diode is then
. See the Typical Operating Circuit. The require-
AVG
AVG
0
1
Extinction Ratio
r
r = P /P
e 1 0
I
e
MOD
ment for compliance in the AC-coupled circuit:
Optical Power of a 1
Optical Power of a Zero
P
P
P = 2P
r /(r + 1)
1
0
1
AVG e e
•
•
•
•
V —Diode bias point voltage (1.2V typ)
D
P = 2P
/(r + 1)
e
0
AVG
R —Diode bias point resistance (5Ω typ)
Optical Amplitude
Laser Slope Efficiency
Modulation Current
Threshold Current
Bias Current
P
P
= P - P
P-P 1 0
L
P-P
L—Diode lead inductance (1nH typ)
η
η = P /I
P-P MOD
I
I
= P /η
R —Series matching resistor (20Ω typ)
D
MOD
MOD
P-P
I
TH
P
I
at I ≥ I
0 TH
I
MOD
2
I
≥ I + I
/2
V
−
× (R + R ) ≥ 1.8V
D L
BIAS
BIAS TH
MOD
CC
Laser to Monitor
Transfer
ρ
I
/P
MD AVG
MON
The time constant associated with the output pullup
inductor and the AC-coupling capacitor, impacts the
pattern-dependent jitter. For this second-order network
use information about the effects of temperature and
aging. The laser driver automatically adjusts the bias to
maintain the constant average power. The new bias con-
dition requires proper compensation of the modulation
current. The designer must predict the slope efficiency of
the laser after its bias threshold current has changed.
The modulation and bias currents under a single operat-
ing condition:
L usually limits the low-frequency cutoff. The capacitor
P
C is selected so:
D
L
P
C
× (R +R ) >
D L
D
(R +R )
D
L
Keep the peak voltage droop less than 3% of the peak-
to-peak amplitude during the maximum CID period t.
The required time constant:
P
re −1
re +1
AVG
η
I
= 2 ×
×
MOD
For AC-coupled diodes:
=I
−t
τ
2.8% = 1− e
I
MOD
2
τ = 35 × t
I
+
BIAS TH
If τ = L /25Ω, and t = 100UI = 40ns, then L = 35µH.
P
P
The required compensation factor is then:
Place a good high-frequency inductor of 2µH on the
transmission line to the laser. Then you can place a
low-frequency inductor of 33µH at a convenient dis-
tance from the driver output.
I
I
− I
MOD1
MOD2
K =
− I
BIAS2
BIAS1
Programming the Bias Current
When the APC loop is enabled, the actual bias current is
reduced from the maximum value to maintain constant
current from the monitor diode. With closed-loop control,
the bias current will be set by the transfer function of the
monitor diode to laser diode current. For example, if the
transfer function to the monitor diode is 10.0µA/mA, then
Once the value of the compensation factor is known, the
fixed portion of the modulation current is calculated from:
I
= I
− K × I
MOD BIAS
MODS
setting I
for 500µA results in I
equal to 50mA.
BIAS
MD
Current Limits
The bias current must be limited in case the APC loop
becomes open. The bias current also needs a set point
in case the APC control is not used. The BIASMAX pin
sets the maximum bias current. The BIASMAX current is
established by an internal current regulator, which main-
tains the bandgap voltage of 1.2V across the external
To allow larger modulation current, the laser is AC-
coupled to the MAX3863. In this configuration, a con-
stant current is supplied from the inductor L . When the
P
MOD pin is conducting, half of I
P
is supplied from
and half is from the laser diode. When MOD is off,
MOD
L
_______________________________________________________________________________________
9
2.7Gbps Laser Driver with Modulation
Compensation
V
CC
V
CC
RTEN
25Ω
V
CC
MODN
MOD
1
0
I
C
D
MUX
MOD
R
D
DATA
DATA
D
D
Q
MAX863
CLK
CLK
V
CC
BIAS
I
V
CC
BIAS
APCFILT1
5Ω
x200
C
APC
APCFILT2
MD
x5
BIASMON
x200
I
∑
CURRENT
MONITOR
MODMON
MDMON
I
MD
500pF
+
MODS
V
V
bg
V
bg
bg
I
MODC
-
R
R
R
R
APCSET
MODSET
MODCOMP
BIASMAX
EN
Figure 3. Functional Diagram
programming resistor. See the I
vs. R
BIASMAX
Programming the Modulation Current
BIASMAX
graph in the Typical Operating Characteristics, and
Two current sources combine to make up the modula-
tion current of the MAX3863 as seen in Figure 3. A con-
stant modulation current programmed at the MODSET
select the value of R
that corresponds to the
BIASMAX
required current at +25°C.
pin and a current, proportional to I
, that varies
BIAS
1.2V
under control by the APC loop. See the Laser Current
Compensation Requirements section for the desired
I
= 200 ×
BIASMAX
R
BIASMAX
values for I
and K. The portion of I
set by
MOD
MODS
MODSET is established by an internal current regulator,
which maintains the bandgap voltage of 1.2V
across the external programming resistor. See the I
Programming the Monitor Diode Current
Set Point
The APCSET pin controls the set point for the monitor
diode current. An internal current regulator establishes the
APCSET current in the same manner as the BIASMAX pin.
vs. R
graph in the Typical Operating
MODSET
MOD
Characteristics and select the value of R
that
MODSET
corresponds to the required current at +25°C. The cur-
rent proportional to I is set by an external resistor at
See the I
vs. R
graph in the Typical Operating
MD
APCSET
BIAS
Characteristics, and select the value of R
that cor-
APCSET
the MODCOMP pin. Open circuiting the MODCOMP
pin can turn off the interaction between I and I
responds to the required current at +25°C.
.
MOD
BIAS
1.2V
I
= 5 ×
MD
R
APCSET
10 ______________________________________________________________________________________
2.7Gbps Laser Driver with Modulation
Compensation
MAX863
V
CC
I
LASER
POWER
MOD1
I
MOD2
P1
T1
T2
50Ω
50Ω
DATA+
DATA-
P
AVG
P0
LASER CURRENT
I
I
BIAS2
BIAS1
GND
Figure 4. Laser Power vs. Current for a Change in Temperature
Figure 5. Equivalent Input Circuit
I
I
= I
+ K × I
MOD MODS BIAS
V
CC
MOD MODN
GND
1.2V
= 200 ×
MODS
R
MODSET
5
K = 200 ×
500+R
MODCOMP
Applications Information
Layout Considerations
To minimize loss and crosstalk, keep connections
between the MAX3863 output and the laser diode as
short as possible. Use good high-frequency layout
techniques and multilayer boards with uninterrupted
ground plane to minimize EMI and crosstalk. Circuit
boards should be made using low-loss dielectrics. Use
controlled-impedance lines for the clock and data
inputs, as well as the module output.
I
MOD
GND
Figure 6. Equivalent Output Circuit
Exposed Pad Package
The exposed pad on the 32-pin QFN provides a very
low thermal resistive path for heat removal from the IC.
The pad is also electrical ground on the MAX3863 and
must be soldered to the circuit board ground for proper
thermal and electrical performance. Refer to Application
Note 862: HFAN-08.1: Thermal Considerations of QFN
and Other Exposed-Paddle Packages for additional
information.
Laser Safety and IEC 825
Using the MAX3863 laser driver alone does not ensure
that a transmitter design is compliant with IEC825. The
entire transmitter circuit and component selections
must be considered. Determine the level of fault toler-
ance required by each application and recognize that
Maxim products are not designed or authorized for use
as components in systems intended for surgical im-
plant 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.
______________________________________________________________________________________ 11
2.7Gbps Laser Driver with Modulation
Compensation
Typical Operating Circuit
V
CC
V
CC
R
R
R
BIASMON
100Ω
MODMON
100Ω
MDMON
4kΩ
L
P
L
P
25Ω
MAX863
50Ω
50Ω
DATA+
DATA-
DATA+
DATA-
25Ω
25Ω
MODN
MOD
0.1μF
0.1μF
V
CC
MAX3892
10Gbps
V
CC
MAX3863
20Ω
SERIALIZER
50Ω
50Ω
CLK+
CLK+
CLK-
BIAS
MD
CLK-
1kΩ
R
PWC
C
APC
0.01μF
REPRESENTS A CONTROLLED-IMPEDANCE TRANSMISSION LINE
Chip Information
Package Information
For the latest package outline information and land patterns, go
TRANSISTOR COUNT: 1786
PROCESS: Bipolar
to www.maxim-ic.com/packages.
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
32 TQFN-EP
T3255-3
21-0140
21-0091
32 QFN-EP
G3255-1
12 ______________________________________________________________________________________
2.7Gbps Laser Driver with Modulation
Compensation
MAX863
Chip Topography
V
BP34
CC
BP22 MDMON
BP21 MD
DATA+ BP35
DATA- BP36
V
V
BP37
BP38
CC
CC
BP20 GND
BP19 V
CC
BP18 MODN
BP17 MODN
GND BP39
81mil
BP16 MOD
BP15 MOD
V
V
BP40
BP41
CC
CC
BP14 V
CC
CLK+ BP42
CLK- BP43
BP13 BIAS
BP12 FAIL
V
BP44
CC
81mil
______________________________________________________________________________________ 13
2.7Gbps Laser Driver with Modulation
Compensation
Pad Coordinates
COORDINATES
COORDINATES
NAME
PAD
NAME
PAD
(μM)
(μM)
GND
APCSET
APCFILT1
APCFILT2
PWC+
BP1
BP2
169, -122
327, -122
465, -122
591, -122
717, -122
913, -122
1109, -120
1235, -120
1361, -120
1500, -120
1660, -120
1797, 50
GND
BP23
BP24
BP25
BP26
BP27
BP28
BP29
BP30
BP31
BP32
BP33
BP34
BP35
BP36
BP37
BP38
BP39
BP40
BP41
BP42
BP43
BP44
1675, 1630
1515, 1630
1374, 1630
1248, 1630
1077, 1630
906, 1630
780, 1630
654, 1630
528, 1630
390, 1630
205, 1630
45, 1501
45, 1375
45, 1249
45, 1123
45, 997
MODMON
BIASMON
BP3
BP4
V
CC
MAX863
BP5
GND
MODCOMP
MODSET
BIASMAX
EN
PWC-
BP6
GND
BP7
V
BP8
CC
MK+
MK-
BP9
BP10
BP11
BP12
BP13
BP14
BP15
BP16
BP17
BP18
BP19
BP20
BP21
BP22
RTEN
GND
FAIL
BIAS
GND
V
CC
1795, 225
1795, 351
1795, 477
1795, 603
1795, 729
1795, 855
1795, 981
1795, 1107
1797, 1328
1797, 1454
DATA+
DATA-
V
CC
MOD
MOD
V
V
CC
CC
MODN
MODN
GND
47, 776
V
V
47, 551
CC
CC
V
47, 425
CC
GND
MD
CLK+
CLK-
47, 299
47, 173
MDMON
V
47, 47
CC
Coordinates are for the center of the pad.
Coordinate 0, 0 is the lower left corner of the passivation opening for pad 1.
14 ______________________________________________________________________________________
2.7Gbps Laser Driver with Modulation
Compensation
MAX863
Revision History
REVISION REVISION
PAGES
DESCRIPTION
CHANGED
NUMBER
DATE
0
1
1/02
Initial release.
—
13
1
10/02
Corrected bond pad 24 to MODMON in the Chip Topography.
Added the PKG CODE column to the Ordering Information table.
Updated the package outline drawing in the Package Information section.
2
3
5/03
15
Added the TQFN package to the Ordering Information table and Absolute
Maximum Ratings.
1, 2
Added the EP description to the Pin Description table.
Changed the formulas in the Current Monitors section.
Added the Exposed Pad Package section.
6
8
1/06
11
Changed the R
100ꢀ, respectively, in the Typical Operating Circuit.
and R
values from 100ꢀ and 4kꢀ to 4kꢀ and
MDMON
BIASMON
12
Removed the dice package from the Ordering Information table and Chip
Information section.
1, 12
12
4
11/08
Removed the package outline drawings and replaced with the table.
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 15
© 2008 Maxim Integrated Products
is a registered trademark of Maxim Integrated Products, Inc.
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