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AKM AK2571 Manual

Single-chip automatic power/temperature control for wdm laser diodes
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AKM Confidential
Single-Chip Automatic Power/Temperature Control
for WDM Laser Diodes
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
Internal 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-selectable wavelength data for tunable laser diodes (four options).
Single 3.3V operation
64-pin LQFP or Bare chip
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
algorithm to control the Thermo-Electric Cooler (TEC). This provides +/- 0.1°C stabilization.. A customer can program the
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>
= Preliminary =
Features
Description
-1-
AK2571
AK2571
2001/11

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  • Page 1 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 algorithm to control the Thermo-Electric Cooler (TEC). This provides +/- 0.1°C stabilization.. A customer can program the appropriate PID parameters into the internal EEPROM , thereby providing compensation characteristics for each Laser Diode.
  • Page 2 AKM Confidential AK2571 Block Diagram AK2571 - Block Diagram - IOUT1 RB (12k) BIAS I-DAC1 BIAS GEN EEPROM Driver IOUT2 Store the PDMON I-DAC2 parameter and Monitor look up table IOUT3 Gain Adj I-DAC3 PDIN STATUS_MON TIMERALM REFOUT Regulator OPALM(Optical out down)
  • Page 3 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.
  • Page 4 AKM Confidential 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 Main name Sub name Bits Example Register REGISTER NAME Sub register name [x,x] R_PDGAIN (Capital letter) R_DAC_SET.Dac1 R_DAC_SET[2:0]...
  • Page 5 AKM Confidential AK2571 All circuit blocks and internal nodes are noted as below Main name Example Circuit Block BLOCK NAME (Capital letter) I-DAC1 Internal Node Signal name (Small letter) vout 2.2 Functional explanation Some values are stored in both register and EEPROM to simplify user programming. Explanations of these values are in the register description tables.
  • Page 6 T_V CONV Internal Temperature Sensor. Outputs a voltage that corresponds to the surface temperature of the AK2571. This function controls temperature compensation of an external current amplifier, driver IC, etc. By activating the E_APC_FF_SET (=1), the ADC outputs the digital data of T_V CONV as the address of EEPROM stores the lookup table of temperature compensation data for external components every 5.6degree.
  • Page 7 3.2 Feed forward APC Function The AK2571 compensates for ambient temperature variations caused by the current amplifier or driver chip located outside of the LD module. If this function is not required, a fixed-current source for the LD can be used instead..
  • Page 8 AKM Confidential AK2571 Table 3-2 R_PDMON_SET setting R_PDMON_SET (E_PDMON_SET)[2:0] PDMON Full Scale 1.1V 0.1V / step 0.4V Table 3-3 R_PDGAIN setting R_PDGAIN_SET (E_PDGAIN_SET)[4:0] Gain 11111 21.7dB 0.7dB / step 00000 Make sure the PDMON voltage equals the value of R(E)_PDMON_SET.
  • Page 9 AKM Confidential AK2571 3.4 Gain setting of I-DAC1,2,3 See the table below for a description on how to set the three I-DACs full-scale voltages. The resolution is set in proportion with the gain. I-DAC1 gain setting R_DAC1_GAIN Gain set value Max...
  • Page 10 AKM Confidential AK2571 3.5 Modulation for dithering through I-DAC1 I-DAC1 has a modulation function for dithering. It’s added to the current of I-DAC1 and output through IOUT1. Its function is available to set R_EA_SW. Figure 3-3 shows the block diagram and Table 3-8 / 3-9 explains the setting...
  • Page 11 The internal temperature sensor’s output voltage function is shown in Figure 3-4. This offset is different for each device, and is adjusted during factory test by AKM. If re-adjustment of the offset is necessary (for higher accuracy, etc.), it is possible to rewrite the R(E)_TV_OFFSET.
  • Page 12 00001 -400 00000 Default value of E_TV_OFFSET is set by AKM. 3.7 Example schematics of connect ion to external components Figures 3-5 to 3-10 illustrate typical system connections. When connecting to a negative voltage source, use a level shifter to ensure that the signal voltages stays within the specified range..
  • Page 13 AKM Confidential AK2571 Figure 3-5 Figure-3-6 Direct Modulation with Positive Power Supply Direct Modulation with Negative Power Supply LD-A AK2571 LD Module IOUT2 I-DAC2 AK2571 IOUT1 I-DAC1 IOUT3 I-DAC3 Driver circuit IOUT2 Driver Circuit I-DAC2 Figure 3-7 Figure 3-8 Direct Modulation with Voltage Controlled LD Driver...
  • Page 14 AKM Confidential AK2571 4. ATC (Automatic Temperature Compensation) Figure 4-1 ATC Block diagram ALM polarity PIDALM TEMPALM Temperature alarm (R_ALM_POL) ALM polarity threshold (R_ALM_POL) TEMPALM PID ALM (E_TMPRTALM_WIN) COMP threshold PIDALM (E_PIDALM_SET) COMP Detect term set ATC_LOCK set (E_LK_CNT_SET) (E_LK_TMPRT_WIN)
  • Page 15 Gain & Offset AK2571 amplifies (x13 typically) the input signal to enable higher resolution from the 8-bit ADC. The input signal should be set to the midpoint of its full scale to meet the target temperature of the offset setting function.
  • Page 16 AKM Confidential AK2571 4.2 PID control Figure 4-2 explains the block diagram for PID control and table 4-3 indicates the parameter setting range Figure 4-2 PID control E_PID_P PID control value Target temperature Proportion (R_PID_VALABS) (R_TMPRT_TRGT) Parameter E_PID_D E_PID_I PID integration...
  • Page 17 AKM Confidential AK2571 4.3 TEC control The TEC control process is illustrated in table 4-4. Figures 4-3 to 4-6 explain the circuit that drives TEC and table 4-5 indicate the pin strapping for different control modes. Figure 4-3 PWM control...
  • Page 18 4.4 Gain & Offset The AK2571 amplifies (typically x13) the input signal from the thermister to provide higher resolution for the 8-bit ADC. It also adds an offset voltage to meet the middle of full scale at target temperature. Table 4-6 indicates temperature levels that correspond to ADC values when using a thermister R0=10kohm@25degree, B=3900 and Table 4-7 indicates a thermister R0=10kohm@25degree, B=3450.
  • Page 19 AKM Confidential AK2571 Table 4-6 Temperature corresponding to code of ADC (Thermister: R0=10kohm@25degree,B=3900) R_ATC_OFFSET Offset voltage Temperature [degree] (typ) ADC=0 ADC=96 ADC=128 ADC=160 ADC=256 0.30 -7.6 -3.2 -1.9 -0.6 0.33 -5.6 -1.5 -0.2 0.36 -3.8 0.39 -2.0 0.42 -0.3 0.45 10.0...
  • Page 20 AKM Confidential AK2571 Table 4-6 Temperature levels corresponding to ADC values (Thermister: R0=10kohm@25degree,B=3450) R_ATC_OFFSET Offset voltage Temperature [degree] (typ) ADC=0 ADC=96 ADC=128 ADC=160 ADC=256 0.30 -11.3 -6.3 -4.7 -3.3 0.33 -9.2 -4.4 -2.9 -1.5 0.36 -7.1 -2.6 -1.2 0.39 -5.2 -0.8...
  • Page 21 AKM Confidential AK2571 4.5 ATC Feedback function The ATC Feedback function compensates for wavelength shifts caused by aging. R_CTRL_USER.Atc_fb = “1” enables the function, “0” disables it. Turning on this function changes the target temperature according to LD aging error from the PD monitor voltage.
  • Page 22 5. Sequencer 5.1 Operation mode The AK2571 has three operation modes shown below. Use the serial interface to change from one mode to another. Figure 5-1 shows the operating flowchart and table 5-1 indicates the circuit block capabilities. 1) Self-operation mode: Operates ATC and APC automatically according to the data stored in EEPROM.
  • Page 23 AKM Confidential AK2571 Table 5-2 Condition ATC status APC status APC_FB ATC_FB APCALM ATCALM of finish Power ON Status-1 ATC Lock ATC Lock Disable Disable Disable User setting User setting (Only work) Status-2 Normal Count up or Disable Disable User setting...
  • Page 24 Control registers Figure 5-3 illustrates the register format. There are two areas in these registers, one is for AKM factory use and the other is for user customization. Even though both areas are re-writable, the AKM values SHOULD NOT BE OVERWRITTEN.
  • Page 25 Digital interface. 2) Common settings 2-1) Write zero (“0”) to all registers R_CTRL_AKM .to stop the AK2571 working. 2-2) Select I-DACx for APC by using the R_DAC_SET register. 2-3) If the temperature corresponding to wave length is known (either exactly or approximately), set the input temperature offset by using the R_ATC_OFFSET register.
  • Page 26 5-5) Change temperature and repeat this sequence. 6) Set another wavelength The AK2571 can store the data for four wavelengths in EEPROM. To get the data for another three wavelengths, repeat the sequence from 2) to 5). Wavelength selection is via pin control.
  • Page 27 AKM Confidential AK2571 5.3.2 Confirmation of other functions 1) OPALM confirmation When the APC adjustments are complete, set R_OPALM_SET. Gradually decrement the value of R_DACx OPALM is output as a current. Confirm LD light power is settled value or not by monitoring the output of PDMON.
  • Page 28 EEPROM address.. Table 7-2 indicate the relationship between WAVE0, 1 and the EEPROM addresses. Addresses from [xx111010] to [xx111111], which contain system data, user program area and AKM factory data, are valid regardless of the settings of WAVE0,1.
  • Page 29 1111 0000 Wavelength-3 data 1001 1010 User program area 1111 0000 Wavelength-4 data 1001 1001 Factory usage by AKM 1111 Table 7-2 Relation of WAVE0, 1and EEPROM [A7, A6] WAVE1 WAVE0 Address 2bit from MSB Remarks Wavelength-1 Wavelength-2 Wavelength-3 Wavelength-4 <Rev.
  • Page 30 AKM Confidential AK2571 7.2 Data construction 1) Temperature compensation data Force the temperature compensation current on the output of DAC1-3 using the internal T_V converter. Digital MSB 4-bits of data from the T_V converter becomes the address of EEPROM and 5-bit (R_TV[3]) selects the 8-bits data whether D15-D8 or D7-D0.

  • Page 31: Table Of Contents

    AKM Confidential AK2571 Refer table 3-7 E_DAC3_GAIN I-DAC3 Gain set 0010 D5-D4 00: 1, 01: 1/2, 10: 1/4 E_EA_SW EA ON/OFF set 0010 0: OFF, 1: ON Refer table 3-9 E_EA_GAIN EA Gain set 0010 D10-D9 00: 16%, 01: 8%...

  • Page 32: E_Apc_Fb_Max

    AKM Confidential AK2571 Table 6-5 Data and address construction for each wavelength Address Data A3-A0 0000 E_ATC_OFFSET[5:0] E_PDMON_SET[2:0] E_PDGAIN[4:0] 0001 E_MON_DAC_FIX[7:0] 0010 E_EA_ E_DACi_GAIN FREQ GAIN DAC3 DAC2 DAC1 E_APC_TRGT［6:0］ 0011 E_APC_FB_MAX[7:0] 0100 E_DAC2_FIX[7:0] E_DAC1_FIX[7:0] 0101 E_DAC3_FIX[7:0] 0110 E_ATC_FB_SET[3:0] E_ATC_FB_MAX[7:0]...

  • Page 33: E_Wl_Alm_Set

    AKM Confidential AK2571 OFFSET Adjusted by AKM adjustment E_MON_SET MON-DAC output 1101 Refer table 6-1 E_STATUS_SET STATUS 1101 Refer table 6-2 output set E_ALM_SHUTDW ALM output set 1110 0x: ALM enable 10: Fix not active polarity 11: Fix active polarity...
  • Page 34 AKM Confidential AK2571 Ｄａｔａ Addrｅss [7:6] [5:4] [3:0] 1010 E_DAC_SET[2:0] Ctrl PWM[1:0] Ana 1011 CNT_SET APC_FB_SET 1100 E_TV_OFFSET[4:0] 1101 E_STATUS_SET E_MON_SET[3:0] 1110 E_OPALM_SET ALM_SH 1111 TIMER_SET 1010 E_APC_CNT_CTRL_USR[7:0] E_INI_CTRL_USR[7:0] 1011 E_FIX_CTRL_USR[7:0] 1100 E_LK_CNT_SET E_LK_TMPRT_WIN[7:0] 1101 E_PID_P[7:0] E_PID_D[7:0] 1110 E_PID_MAX[5:0] E_PID_I[7:0]...
  • Page 35 00: I-DAC1 select 01: I-DAC2 10: I-DAC3 11: disable R_TV_OFFSET[4:0] Internal T_V conv. Offset 000110 Refer table 3-10 adjustment AKM factory usage R_MON_SET[3:0] MON-DAC output set 000111 Refer table 6-1 R_STATUS_SET[6:4] STATUS MON output set 000111 Refer table 6-2 R_ALM_SHUTDW[1:0] 2...
  • Page 36 AKM Confidential AK2571 R_DAC3[7:0] I-DAC3 set 001110 R_STATUS[7:0] Status register 010000 R_ALM_ST[3:0] 010001 R_TMPRT_CRNT[7:0] Theremistor temperature data 010010 R_TV[7:0] Internal conv. 010011 Temperature data R_APC_CMPNST[7:0] LD aging error current 010100 R_ATC_CMPNST[7:0] Target temperature shift value 010101 R_MON_DAC[7:0] Monitor DAC set...
  • Page 37 AKM Confidential AK2571 Table 8-2 Register Map Ｄａｔａ Addrｅss R･W [5:4] [3:0] 15 14 13 12 11 00 0000 R_ATC_OFFSET[5:0] R_PDMON_SET[2:0] R_PDGAIN[4:0] 0001 R_MON_DAC_FIX[7:0] 0010 R_EA_ R_DACi_GAIN FREQ GAIN DAC3 DAC2 DAC1 R_APC_TRGT［6:0] 0011 0100 R_DAC_SET[2:0] Ctrl PWM[1:0] Ana 0101...
  • Page 38 AKM Confidential AK2571 CSN must be set for each instruction. It cannot be used continuously. Digital I/F can connect directly to a SPI interface In this case, set (CPOL, CPHA) = (0, 0) or (1, 1). (CPOL, CPHA) = (0, 0) : Status output through DO pin (CPOL, CPHA) = (1, 1) : Status output disable 1.1 Register access [READ] mode （RDREG)
  • Page 39 AKM Confidential AK2571 1.3 EEPROM access mode（WRDS、WREN command） I3 I2 I1 I0 0 0 0 0 ： WRDS 0 0 1 1 ： WREN 1.4 EEPROM access [WRITE] mode （WRITE） High-Z Te/w READY READY 1.5 EEPROM access [READ] mode（READ） High-Z <Rev.
  • Page 40 AKM Confidential AK2571 1.6 Move operation mode I3 I2 I1 I0 0 0 0 0 ： Self operation（NORMAL） 0 1 1 1 ： Register access（REGMODE） 1 1 1 0 ： EEPROM mode（EEPMODE） <Rev. 0.6E Preliminary> -40- 2001/11...
  • Page 41 After its release, AK2571 start from reset. 2.3 Shut down control through SHUT_APCN pin SHUT_APCN=”0” make AK2571 only APC shut down which stop the current output through I-DAC1-3. After its release, AK2571 start to work by the data before shut down soon.
  • Page 42 AKM Confidential AK2571 Electric Characteristics (1) Absolute maximum rating Parameter Symbol Unite Remarks Voltage supply VDD=all VDD (AVDD, L1DD, L2VDD, L3VDD, TVDD, -0.3 DVDD) Grand level GND=all VSS (AVSS, BVSS, LVSS, TVSS, DVSS, =all GND DAVSS ) Input voltage（Beside VDDs）...
  • Page 43 AKM Confidential AK2571 (6) Digital Input / Output AC characteristics（Beside Serial Interface） Parameter Symbol Unite Remarks Reset pulse width Tpwr RESETN ns Refer figure 1 Note) Duty Cycle：（Tpwh／(Tpwh＋Tpwl））×100 % Tpwh Tpwl RESETN Tpwr Figure 1 Reset pulse width Figure 2 Input Clock Duty Cycle (7) Digital Input / Output AC characteristics（Serial Interface）...
  • Page 44 AKM Confidential AK2571 Tskw Tskw Tskp Tcss Tdih Tdis High-Z Figure 3: input command timing Tcsh 不定 High-Z Figure 4: data output timing Tcsh Te/w Tdis Tdih 不定 High-Z Trch READY Figure 5: EEPROM write timing <Rev. 0.6E Preliminary> -44-...
  • Page 45 AKM Confidential AK2571 Tsksl Invalid High-Z High-Z READY Figure 6: status output through DO pin * Status output Monitoring DO pin, indicates the status of READY. After the WRITE command is executed, SK is fixed Low and CSN moves from High to Low, DO pin changes to status output mode and outputs a READY signal.
  • Page 46 AKM Confidential AK2571 *1) AMON output voltage *2) Center voltage of Output ”Vmon” is indicated by the expression below, if DAC code = ”K”. Vmon = (2.1 - 0.5 ) / 255 * K + 0.5 [V] (10) DAC_APC characteristics...
  • Page 47 AKM Confidential AK2571 (12) EA_MOD characteristics Dithering current by EA_MOD function is added to current of I-DAC1and output through IOUT1pin. Output current through I-DAC1 shifts if this function is enabled by the register R_EA_SW(E_EA_SW). (1) Dithering Frequency The dither frequency is selected through register (EEPROM) R_(E_) EA_FREQ, and is derived by dividing the OSC 2.048MHz(typ) clock.
  • Page 48 *1) SHUT DOWN release time is regulated in SHUT_APCN. (16) T_V conversion characteristics Parameter Condition Unite Remark T_V Conv. gain Offset adjustment -0.7 °C/step ±5% Design target Regulated by the digital data after A-to-D conversion. Its offset is adjusted by AKM in testing. <Rev. 0.6E Preliminary> -48- 2001/11...
  • Page 49 REFOUT pin ±5% thermister Design target *1) PDIN voltage is user programmable by register setting(Refer 3.3.1) in the range of 0.4 to1.1V by 0.1V/step. (18) Internal oscillator (OSC) characteristics (AKM adjust in testing) Parameter Condition Unite Remark Frequency Adjusted by AKM in testing 2.048...
  • Page 50 Shut down APC. ”L” = Shut down. SHUT_ATCN Shut down ATC and APC. ”L” = Shut down. RESETN Reset input. ”L”= reset AKM Test pin. Connect to GND in ordinary L1VDD Voltage supply for I-DAC1 NC pin. Connect to GND. PDIN Monitors PD voltage input.
  • Page 51 “H” output when the AK2571 is in EEPROM mode. STATUS_MO Monitors the AK2571 status. TIMERALM Timer ALM. Outputs an alarm if the AK2571 doesn’t enter normal operating mode within the settling period. OPALM Loss of power. Outputs an alarm if the voltage from PDIN is below the threshold.
  • Page 52 AKM Confidential AK2571 Package Conditions 1) Package : 64-LQFP 2) Marking a.1pin indicate: Marked ○ is 1pin b. AKM trademark: AKM c. AKM marking: AK2571 d. Date code: YYWWXXX YY: Year WW: Week(1～52) XXX： LOT code 12.0 ±0.4 10.0 AK2571 YYWW 0゜～10゜...

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