AK2571 Datasheet, PDF (6/52 Pages) Asahi Kasei Microsystems – Single-Chip Automatic Power/Temperature Control for WDM Laser Diodes

AKM Confidential
AK2571
3.1 Functional description
Block
Function
Note
T_V CONV
ADC
EEPROM
ADDER
I-DAC1
I-DAC2
I-DAC3
EA_MOD
PDGAIN
DACAPC
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. This data is output through
I-DAC and supplies the Laser Diode modulation and BIAS currents. If this function is not
required set E_APC_FF_SET to a fixed value and set the current value in E_DACx_FIX.
8-bits A-to-D converter for temperature detection. (5-bit MSB is used for temperature
compensation)
E_APC_FF_SET=0 (Default): APC is not activated. Fixed data (E_DACx_FIX, x=1-3) is sent
to I-DACs.
E_APC_FF_SET=1: APC activation. 5-bits MSB of ADC sent to E_DACxTV[A/D], x=1-3
and work the APC sequence.
E_APC__FB_SET.Dacx(x=1-3)=0 (default): Do not add aging compensation current to
I-DACs.
E_APC_FB_SET.Dacx(x=1-3)=1: Add aging compensation (R_APC_CMPNST) current to
I-DACs.
8-bit current output DAC (120mA max.). Output current corresponds to R_DAC1 data.
When R_DAC_SET=1, this outputs is enabled.
8-bit current output DAC (20mA max.). Output current corresponding to R_DAC1 data.
When R_DAC_SET=1, this outputs is enabled.
8 bit current output DAC (20mA max.). Output current corresponding to R_DAC1 data.
When R_DAC_SET=1, this outputs is enabled.
Dithering function. R_EA_SW=0: Non-Active/ 1: Active. R_EA_FREQ: Modulation
frequency selection: 16kHz(000), 32kHz(001), 64kHz(010), 128kHz(011) and 256kHz(100).
R_EA_GAIN: Additional level to I=DAC1 out selection:16%(00), 8%(01), 10.4%(10) and
2%(11).
Amplifies the input signal from the monitoring Photo Diode. (vpd).
Customers can set the gain from 0dB to 21dB(Typ.) by 0.7dB steps, using values stored in the
EEPROM.
Input range: 0.2V - 1.5V
Full-scale output through PDMON can be set from 0.4V to1.1V in 0.1V steps. Internal
attenuator adjusts the full scale per E_PDMON_SET..
Generates the target APC (R_APC_TRGT) voltage (vact_ref) in proportion to PDGAIN.
APC_COMP
DIGITAL
FILTER
CUALM_COMP
OPALM_GAIN
OPALM_COMP
Compares the PD monitoring voltage (vpd) with APC target voltage (vapc_ref), if vpd <
vapc_ref, outputs UP signals to digital filter. And if vpd > vapc_ref, outputs DOWN signals to
digital filter. The sampling rate is 512kHz.
Receives signals from APC_COMP, calculates the value to make vpd and vapc_ref equal. Its
value is the LD aging error (R_APC_CMPNST), and is limited by the value of
E_APC_FB_MAX. There is no need to supply negative current for aging error.
LD aging error current (R_APC_CMPNST) over Alarm value (E_CUALM_SET), output
CUALM. Its polarity is selected by register R_ALM_POL.
OPALM (light sparkle fail) output level (vopalm_ref) setting by register R_OPALM_SET.
000: 1/2, 001: 1/3, 010: 1/4, 011: 1/5, 100: 1/6, 101:1/8
Compares the PD monitoring voltage (vpd) with OPALM voltage (vpalm), if vpd < vpalm,
outputs OPALM (light power down alarm). Its polarity is selected by register R_ALM_POL.
<Rev. 0.6E Preliminary>
-6-
2001/11