AK2571 Datasheet PDF - AKM


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AK2571
AKM

Part Number AK2571
Description Single-Chip Automatic Power/Temperature Control
Page 30 Pages

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AK2571
= Preliminary =
AK2571
Single-Chip Automatic Power/Temperature Control
for WDM Laser Diodes
Features
Single Chip LSI that integrates APC (Auto Power Control) and ATC (Auto Temperature Control) functions for
WDM Laser Module
A controlling TEC (Thermal Electrical Cooler) stabilizes the temperature of LD module in the range of +/-0.1°C
by PID algorithm.
Parameters controlling Laser Diode are user programmable and stored in EEPROM
www.DataSheIent4teUr.ncoaml Temperature Sensor detects on-chip temperature, enabling compensation internal and external
components that may be affected by changing ambient temperature.
Autonomous operation (internal oscillator and logic).
Pin-selectablewavelengthdata fortunablelaserdiodes(fouroptions).
Single 3.3V operation
64-pin LQFP or Bare chip
Description
The AK2571 is a single-chip solution for WDM Laser Diode Module applications. It integrates both ATC (Auto
Temperature Control) and APC (Auto Power Control) functions in a small 64-pin LQFP or bare die package..
The ATC function of the AK2571 detects the LD module temperature via an external thermister and uses the PID
algorithmto controlthe Thermo-Electric Cooler(TEC).Thisprovides +/-0.1°C stabilization.. Acustomercan programthe
appropriate PID parameters into the internal EEPROM , thereby providing compensation characteristics for each Laser
Diode. TEC control is handled through either PWM or Analog current control through I-DAC4. These are easily selected
by an EEPROM (Register) setting.
The APC has two functions. The first function is to compensate for Laser Diode power decreases caused by aging. The
other function is to compensate for temperature variations of AK2571 and external components (current amplifier or
driver circuits) which may be affected by ambient temperature within the LDM. The AK2571 does this by controlling
BIAS and modulation current according to the look up table in EEPROM .
The AK2571 has every alarm needed for WDM modules (Loss of power, Over current, Temperature etc.). There is a
dithering function for modulation current that improves the extinction ratio for long distance transmissions.
Also, parameter and compensation data can be stored for four wavelengths. If a customer uses a tunable laser diode, it is
very easy to change the wavelength by pin control.
<Rev. 0.6E Preliminary>
-1-
2001/11



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Block Diagram
AK2571
AK2571 - Block Diagram -
RB (12k) BIAS
BIAS GEN
Monitor
PD
PDMON
Gain Adj
RPD PDIN
CPD
REFOUT
Regulator
www.DataSheet4U.com
Rth
TEMPIN Gain &
OFFSET
Adj
RL
T-V
Conv.
EEPROM
Store the
parameter and
look up table
ADC
WAVE1
WAVE0
SHUT_APCN
SHUT_ATCN
OSC
Digital I/F
MODE
STATUS
CSN SKN DI DO READY REG EEP
I-DAC1
IOUT1
IOUT2
APC I-DAC2
I-DAC3
IOUT3
Driver
+
LD
Alarm Decision
STATUS_MON
TIMERALM
OPALM(Optical out down)
CUALM(Over Current)
TEMPALM(Temperature ALM
PIDALM(TECControl current ALM)
WLALM(Target Temperature ALM)
HEATP
PWM
or
COOLP
PID Current
direction
control
COOLN
HEATN
TEC
Monitor
DAC
AMON
IOUT4H
I-DAC4
IOUT4C
Curret
Amp/
Bypass
<Rev. 0.6E Preliminary>
-2-
2001/11



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AK2571
Circuit Description
1. Overview
The AK2571 has two primary functions. The first function is APC (Automatic Temperature Control) which supplies
adequate modulation /BIAS current to a Laser diode and the other is ATC (Automatic Temperature control) which
controls the TEC (Thermo Electric Cooler) to stabilize the temperature of the Laser diode.
1. 1 APC
There are three Digital to Analog Converters (I-DAC1, 2, 3) that output the current for modulation, BIAS and EA
(Electrical Absorption) Modulation.
Maximum output currents :
I-DAC1: 120mA (typ.),
www.DaIt-aDSAheCe2t4aUn.cdoIm-DAC3: 20mA (typ.)
Each DAC has a current limit function whose value is stored in the internal EEPROM. This is especially important for
I-DAC1, which has the modulation function for dithering.
In WDM systems, there is no need for discrete laser diode temperature compensation. However the outer current
amplifier or LD drivers may be affected by ambient temperature changes. In order to compensate for these the AK2571
has a feed-forward APC that can supply adequate current corresponding to the ambient temperature change detected by
the internal T_V converter.
Please refer the part “3. APC” for details.
1.2 ATC
The AK2571 controls TEC to stabilize the input voltage from the temperature sensor of the LD module (Thermistor). The
control algorithm is PID (Proportion Integration Differential) which has user-programmable parameters that are stored in
EEPROM. There are two ways for driving TEC, one is PWM (more energy effective than DC drive), the other is DC
current drive through I-DAC, which has lower noise.
Please refer the part “4. ATC” for details.
1.3 ControlSequence
There are three functional modes in AK2571 below.
1) Self-operation mode: The AK2571 operates ATC and APC independently. When self-operating mode starts, , ATC Lock
(detectswhen the target temperature is reached), APC Count up (preventsjumps in BIAS and Modulation currents) and
Timer (countsthetimefromdevicestarttobeginningofoperation)areavailable.
2) Register Access Mode: AK2571 permits writing registers through the digital interface. Customers can adjust any
parameters or tables in this mode.
3) EEPROM mode: AK2571 permits EEPROM writes. Customers can store the parameters or table data in EEPROM.
Please refer the part “5. Sequencer” for details.
<Rev. 0.6E Preliminary>
-3-
2001/11



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AK2571
2. Reference
2.1 Definition
All values are expressed in the order shown below
Tab_(Function Block_)Main name(Function_).Sub name[Bit]
Setting way
Tab Mainname
Sub name
Bits Example
Register
R REGISTER NAME Subregistername [x,x] R_PDGAIN
(Capital letter)
R_DAC_SET.Dac1
R_DAC_SET[2:0]
EEPROM
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E EEPROM NAME Subeepromname [x,x] E_PDGAIN
(Capital letter)
E_DAC_SET.Dac1
PIN P PIN NAME (Capital
letter)
P_WAVE0
Register and EEPROM names may include additional tags as described below
Classify
AdditionalTag Contents
Example
FunctionBlock APC
APC relate
E_APC_FF_SET
DAC
I-DAC relate
E_DAC1_FIX
ATC ATCrelate
E_ATC_OFFSET
ALM
Alarm relate
E_ALM_POL
PID PIDrelate
E_PID_P
LK ATCLockcounterrelate
E_LK_CNT_SET
TMPRT
Temperature decode value
R_TMPRT_TRNT
Function
SET
Settled value (ALM or Counter etc.)
E_DAC1_SET
WIN
Hysteresis (ALM or counter etc.)
E_TMPRTALM_WIN
CTRL
Hysteresis (ALM or counter etc.)
E_INI_CTRL_USR
FIX FixeddataforAPC
E_DAC1_FIX
TV APCcompensationdata
E_DAC1_TV
CMPNST
LD aging compensation data
R_APC_CMPNST
TRGT
Targetvalue(TemperatureorVoltageetc.) E_APC_TRGT
CRNT
Current value
R_TMPRT_CRNT
BFR Beforevalue
R_TMPRT_BFR
<Rev. 0.6E Preliminary>
-4-
2001/11




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