AKM Confidential
AK2571
3.1 Functional description
Block Function
Note
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. 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.
ADC
8-bits A-to-D converter for temperature detection. (5-bit MSB is used for temperature
compensation)
EEPROM
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.
ADDER 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.
I-DAC1
8-bit current output DAC (120mA max.). Output current corresponds to R_DAC1 data.
When R_DAC_SET=1, this outputs is enabled.
I-DAC2
8-bit current output DAC (20mA max.). Output current corresponding to R_DAC1 data.
When R_DAC_SET=1, this outputs is enabled.
I-DAC3
8 bit current output DAC (20mA max.). Output current corresponding to R_DAC1 data.
When R_DAC_SET=1, this outputs is enabled.
EA_MOD
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).
PDGAIN
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..
DACAPC
Generates the target APC (R_APC_TRGT) voltage (vact_ref) in proportion to PDGAIN.
APC_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.
DIGITAL
FILTER
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.
CUALM_COMP 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_GAIN
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
OPALM_COMP 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
