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PDF MAX3766 Data sheet ( Hoja de datos )
| Número de pieza | MAX3766 | |
| Descripción | 622Mbps LAN/WAN Laser Driver | |
| Fabricantes | Maxim Integrated | |
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19-1249; Rev 1; 11/04
EVAALVUAAILTAIOBNLEKIT 622Mbps LAN/WAN Laser Driver with
Automatic Power Control and Safety Shutdown
________________General Description
The MAX3766 is a complete, easy-to-program laser
driver for fiber optic LAN transmitters, optimized for
operation at 622Mbps. It includes a laser modulator,
automatic power control (APC), and a failure indicator
with latched shutdown.
Laser modulation current can be programmed up to
60mA at 622Mbps. A programmable modulation tem-
perature coefficient can be used to keep the transmit-
ted extinction ratio nearly constant over a wide
temperature range. The modulator operates at data
rates up to 1.25Gbps at reduced modulation current.
APC circuitry uses feedback from the laser’s monitor
photodiode to adjust the laser bias current, producing
constant output power regardless of laser temperature
or age. The MAX3766 supports laser bias currents up
to 80mA.
The MAX3766 provides extensive laser safety features,
including a failure indicator with latched shutdown and
a smooth start-up bias generator. These features help
ensure that the transmitter output does not reach haz-
ardous levels. The MAX3766 is available in a compact
20-pin QSOP and dice.
________________________Applications
622Mbps ATM Transmitters
1.25Gbps Fiber Optic LAN Transmitters
1.25Gbps Ethernet Transmitters
Typical Application Circuits appear at end of data sheet.
____________________________Features
♦ 60mA Modulation Current
♦ 80mA Bias Current
♦ 200ps Edge Speed
♦ Modulation-Current Temperature Compensation
♦ Automatic Power Control
♦ Laser-Fail Indicator with Latched Shutdown
♦ Smooth Laser Start-Up
PART
MAX3766EEP
MAX3766EEP+
MAX3766E/D
Ordering Information
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
20 QSOP
20 QSOP
Dice*
*Dice are designed to operate over this range, but are tested and
guaranteed at TA = +25°C only. Contact factory for availability.
+Denotes lead-free package.
Pin Configuration
TOP VIEW
BIASMAX 1
TC 2
REF2 3
MOD 4
GND 5
IN- 6
IN+ 7
GND 8
VCC 9
ENABLE 10
MAX3766
20 REF1
19 POWERSET
18 MD
17 GNDOUT
16 BIAS
15 OUT+
14 OUT-
13 VCCOUT
12 FAIL
11 SAFETY
QSOP
________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.
1 page  
622Mbps LAN/WAN Laser Driver with
Automatic Power Control and Safety Shutdown
Typical Operating Characteristics (continued)
(Typical Operating Characteristics are measured on the MAX3766 evaluation kit, VCC = +5.0V, TA = +25°C, unless otherwise noted.)
BIAS CURRENT vs. RBIASMAX
(NO APC, OPEN-LOOP CONFIGURATION)
100
MONITOR CURRENT vs. TEMPERATURE
10
NOMINAL = 1mA
1
10
1
1
NOMINAL = 200µA
0.1
NOMINAL = 20µA
0.01
NOMINAL = 2µA
0.001
10 100 1k 10k 100k
-40 -20 0 20 40 60 80 100
RBIASMAX (Ω)
AMBIENT TEMPERATURE (°C)
DATA-DEPENDENT JITTER
vs. TEMPERATURE (CMD = 0.1µF)
260
240
220
200 223- 1 PRBS PATTERN
180
160 213 PRBS PATTERN
72 CONSECUTIVE ZEROS
140
120
100
-40
-20 0 20 40 60 80
AMBIENT TEMPERATURE (°C)
100
UNSUCCESSFUL STARTUP
VENABLE
VMD
FAIL
VSAFETY (τ = 30µs)
SUCCESSFUL STARTUP
VENABLE
FAIL
VMD
VSAFETY (τ = 1500µs)
SMOOTH STARTUP
100µW/
div
OPTICAL OUTPUT WITH DATA ON
OPTICAL OUTPUT WITH DATA OFF
DATA OUT (AC COUPLED)
DATA OUT (AC COUPLED)
10µs/div
50µs/div
5µs/div
ABRUPT SHUTDOWN
OPTICAL OUTPUT WITH DATA ON
100µW/
div
OPTICAL OUTPUT WITH DATA OFF
5µs/div
REFERENCE VOLTAGE
vs. TEMPERATURE
3.40
3.20
VREF1
3.00
2.80
2.60
2.40
VREF2
2.20 RTC = OPEN
2.00
-45 -25 -5 20 40 60 80
AMBIENT TEMPERATURE (°C)
100
_______________________________________________________________________________________ 5
5 Page 
622Mbps LAN/WAN Laser Driver with
Automatic Power Control and Safety Shutdown
VCC
OR
ENABLE
VCC
MAX809MEUR-T
RESET
ENABLE
MAX3766*
SAFETY
CSAFETY
*IN LATCHED SHUTDOWN
CONFIGURATION
Figure 6. Reset Pulse Generator
If PC board space is not a constraint, Maxim recom-
mends enabling the transmitter with a reset-pulse gen-
erator, such as the MAX809, which generates a reset
signal after VCC reaches 4.5V (Figure 6). This method
ensures that the transmitter starts correctly, even if the
supply ramps very slowly.
__________________Design Procedure
Select Laser
Select a communications-grade laser with a rise time of
0.5ns or better for 622Mbps applications. The voltage
swing at the OUT+ pin affects the output waveform,
and is largely determined by the laser resistance,
inductance, and modulation current. To obtain the
MAX3766’s AC specifications, the output voltage at
OUT+ must remain above VCC - 2.5V at all times.
An approximation for the minimum voltage at OUT+ is
given by the following equation (Table 1):
( )VOUT(MIN) = VCC(MIN) - VLASER - IMOD
⎛
⎝⎜RL
+
RD
+
L
tr
⎞
⎠⎟
Select a laser that meets the output voltage criteria. A
high-efficiency laser requires low modulation current
and generates low voltage swing at OUT+. Laser pack-
age inductance can be reduced by trimming leads.
Typical package leads have inductance of 25nH per
inch (1nH/mm). A compensation filter network can also
be used to reduce ringing, edge speed, and voltage
swing.
Table 1. Output Voltage Approximation
VARIABLE
VOUT(MIN)
VCC(MIN)
VLASER
RL
IOUT
RD
L
tr
DESCRIPTION
Approximation for the lowest voltage at the OUT+ pin
Minimum power supply
Laser forward voltage at operating power
Laser dynamic resistance
Laser modulation current
Any damping resistance or line termination in series with the laser
(but not in series with BIAS)
Total series inductance of laser, laser package, and board traces to the
MAX3766
20% to 80% rise time of the laser modulation current, filtered by a
compensation network
TYPICAL VALUE
2.2V
4.5V
1.3V
3Ω
30mA
10Ω
6nH
300ps
(20% to 80%)
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet MAX3766.PDF ] | |
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