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AIC809-46CUTR , 3-PIN MICROPROCESSOR RESET CIRCUITS
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AIVR3K42 , APLUS INTEGRATED CIRCUITS INC
AK002M4-31 , GaAs MMIC Control FET in SOT 143 DC-2.5 GHz
ADN2841ACP-32-ADN2841ACP-48
Dual-Loop 50 Mbps.2.7 Gbps Laser Diode Driver
REV.0
Dual-Loop 50 Mbps–2.7 Gbps
FUNCTIONAL BLOCK DIAGRAM
FEATURES
50 Mbps to 2.7 Gbps Operation
Typical Rise/Fall Time 80 ps
Bias Current Range 2 to 100 mA
Modulation Current Range 5 to 80 mA
Monitor Photodiode Current 50 �A to 1200 �A
Closed-Loop Control of Power and Extinction Ratio
Laser Fail and Laser Degrade Alarms
Automatic Laser Shutdown, ALS
Dual MPD Functionality for DWDM
Optional Clocked Data
Full Current Parameter Monitoring
5 V Operation
48-Lead LFCSP Package
32-Lead LFCSP Package (Reduced Functionality)
APPLICATIONS
DWDM Dual MPD Wavelength Fixing
SONET OC-1/3/12/48
SDH STM-1/4/16
Fiber Channel
Gigabit Ethernet
GENERAL DESCRIPTIONThe ADN2841 uses a unique control algorithm to control both
average power and extinction ratio of the laser diode (LD) after
initial factory set up. External component count and PCB area are
low as both power and extinction ratio control are fully integrated.
Programmable alarms are provided for laser fail (end of life) and
laser degrade (impending fail).
The ADN2841 has circuitry for a second monitor photodiode
which enables DWDM wavelength control.
Laser Diode Driver
ADN2841–SPECIFICATIONS
(VCC = 5 V � 10%. All specifications TMIN to TMAX unless otherwise noted1. Typical
values as specified at 25�C.)
ADN2841NOTESTemperature Range: –40°C to +85°CWhen the voltage on DATAP is greater than the voltage on DATAN, the modulation current flows in the IMODP pin.Guaranteed by design and characterization. Not production tested.IDTONE may cause eye distortion.ICC for power calculation is the typical ICC given.All VCCS should be shorted together.
Specifications subject to change without notice.
ABSOLUTE MAXIMUM RATINGS1(TA = 25°C unless otherwise noted.)
VCCtoGND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7 V
OperatingTemperatureRange
Industrial . . . . . . . . . . . . . . . . . . . . . . . . . . –40°Cto+85°C
StorageTemperatureRange . . . . . . . . . . –65°Cto+150°C
Junction Temperature (TJ MAX) . . . . . . . . . . . . . . . . . . 150°C
48-LeadLFCSPPackage
Power Dissipation . . . . . . . . . . . . . . .(TJ MAX – TA)/θJA mW
θJA Thermal Impedance2 . . . . . . . . . . . . . . . . . . . .25°C/W
Lead Temperature (Soldering for 10 sec) . . . . . . . . 300°C
ORDERING GUIDE32-Lead LFCSP Package
Power Dissipation . . . . . . . . . . . . . . .(TJMAX–TA)/θJAmW
θJA Thermal Impedance2 . . . . . . . . . . . . . . . . . . . .32°C/W
Lead Temperature (Soldering for 10 sec) . . . . . . . . . 300°C
NOTES
1Stresses above those listed under Absolute Maximum Ratings may cause perma-
nent damage to the device. This is a stress rating only; functional operation of the
device at these or any other conditions above those listed in the operational
sections of this specification is not implied. Exposure to absolute maximum rating
conditions for extended periods may affect device reliability. Transient currents of
up to 100 mA will not cause SCR latch-up.
2θJA is defined when the part is soldered onto a four-layer board.
CAUTIONESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000V readily
accumulate on the human body and test equipment and can discharge without detection. Although
the ADN2841 features proprietary ESD protection circuitry, permanent damage may occur on
devices subjected to high-energy electrostatic discharges. Therefore, proper ESD precautions are
Figure 1.Setup and Hold Time
ADN2841
PIN FUNCTION DESCRIPTIONS
PIN CONFIGURATIONS
48-Lead LFCSP
PIN 1
ADN2841
TOP VIEW
(Not to Scale)
GND2 37
VCC2 38
IMODN 39
IMODN 40
GND2 41
IMODP 42
IMODP 43
GND2 44
GND2 45
IBIAS 46
IBIAS 47
CCBIAS 48
GND 1
LBWSET 2
ASET 3
ERSET 4
PSET 5
GND 6
IMPD 7
IMPDMON 8
IMPDMON2 9
IMPD2 10
GND4 11
VCC4 12
24 GND
23 GND
22 CLKN
21 CLKP
20 GND1
19 DATAP
18 DATAN
17 GND1
16 VCC1
15 GND
14 PAVCAP
13 ERCAP
36 GND235 IDT
ONE
34 GND233 IBMON32 IMMON31 GND330 VCC329 ALS28 F
AIL
27 DEGRADE26 CLKSEL25 GND
32-Lead LFCSP
PIN 1
INDICATOR
TOP VIEW
(Not to Scale)
LBWSET 1
ASET 2
ERSET 3
32 CCBIAS
ERCAP 9
VCAP 10VCC1 11
GND1 1
CLKP 15CLKN 16
PSET 4
IMPD 5
IMPDMON 6
GND4 7
VCC4 8
31 IBIAS30 GND229 GND228 IMODP27 GND226 IMODN25 VCC2
ADN2841
24 IBMON
23 IMMON
22 GND3
21 VCC3
20 ALS
19 FAIL
18 DEGRADE
17 CLKSEL
PIN FUNCTION DESCRIPTIONS (continued)
ADN2841
LOOP BANDWIDTH SELECTIONFor anyrate operation the user should hardwire the LBWSET
pin high and use 1 µF capacitors to set the actual loop band-
width. These capacitors are placed between the PAVCAP and
ERCAP pins and ground. It is important that these capacitors
be low-leakage multilayer ceramics with an insulation resistance
greater than 100 GΩ or a time constant of 1000 sec, whichever
is less.The ADN2841 may be optimized for 2.7 Gbps operation
by keeping the LBWSET pin low. This results in a much shorter
loop time constant (a 10� reduction). The value of PAVCAP
and ERCAP capacitors required for 2.5 Gbps operation is 22 nF.
ALARMSThe ADN2841 alarms are designed to allow interface compliance
to ITU-T-G958 (11/94) section 10.3.1.1.2 (transmitter fail) and
section 10.3.1.1.3 (transmitter degrade). The ADN2841 has
two active high alarms, DEGRADE and FAIL. A resistor between
ground and the ASET pin is used to set the current at which
these alarms are raised. The current through the ASET resistor is
a ratio of 100:1 to the FAIL alarm threshold. The DEGRADE
alarm will be raised at 90% of this level.
Example:
NOTE: The smallest value for RASET is 1.2 kΩ, as this corre-
sponds to the IBIAS maximum of 100 mA.
The laser degrade alarm, DEGRADE, gives a warning of imminent
laser failure if the laser diode degrades further or environmental
conditions continue to stress the LD, e.g., increasing temperature.
The laser fail alarm, FAIL, is activated when the transmitter can
no longer be guaranteed to be SONET/SDH-compliant. This
occurs when one of the following conditions arises:The ASET threshold is reached.The ALS pin is set high. This shuts off the modulation and
bias currents to the LD, resulting in the MPD current dropping
to zero. This gives closed-loop feedback to the system in which
ALS has been enabled.
DEGRADE will only be raised when the bias current exceeds
90% of ASET current.
MONITOR CURRENTSIBMON, IMMON, and IMPDMON and IMPDMON2 are
current controlled current sources from VCC. They mirror the
bias, modulation, and MPD current for increased monitoring
functionality. An external resistor to GND gives a voltage pro-
portional to the current monitored.
DUAL MPD DWDM FUNCTION (48-PIN LFCSP ONLY)The ADN2841 has circuitry for an optional second monitor
photodiode, MPD2.
GENERALLaser diodes have current-in to light-out transfer functions as shown
in Figure 2. Two key characteristics of this transfer function are the
threshold current, ITH, and slope in the linear region beyond the
threshold current, referred to as slope efficiency, LI.
ER =
ITHCURRENT
PAV
OPTICAL PO
WERFigure 2.Laser Transfer Function
CONTROLA monitor photodiode (MPD) is required to control the LD. The
MPD current is fed into the ADN2841 to control the optical
power and extinction ratio, continuously adjusting the bias current
and modulation current in response to the laser’s changing
threshold current and light-to-current (LI) slope (slope efficiency).
The ADN2841 uses automatic power control (APC) to main-
tain a constant power over time and temperature.
The ADN2841 uses closed-loop extinction ratio control to allow
optimum setting of extinction ratio for every device. Hence
SONET/SDH interface standards can be met over device varia-
tion, temperature, and time. Closed-loop modulation control
eliminates the need to either overmodulate the LD or include
external components for temperature compensation. This reduces
research and development time and second-sourcing issues
caused by characterizing LDs.
Average Power and Extinction Ratio are set using the PSET and
ERSET pins, respectively. Potentiometers are connected between
these pins and ground. The potentiometer, RPSET, is used to
change the average power. The potentiometer, RERSET , is used
to adjust the extinction ratio. Both PSET and ERSET are
kept 1.23 V above GND.
RPSET and RERSET can be calculated using the following formulas:
where IAV is average MPD current.
where PCW is the dc optical power specified on the laser data
sheet, IMPD_CW is MPD current at that specified PCW, and PAV is
the required average power.
Note that IERSET and IPSET will change from device to device.
However, the control loops will determine actual values. It is not
required to know exact values for LI or MPD optical coupling.
