AK2573A Datasheet, PDF (36/38 Pages) Asahi Kasei Microsystems – 125M / 156M Laser Diode Driver + APC

ASAHI KASEI
[AK2573A]
10. Module Adjustment Example
Table 10-1 shows the module adjustment example.
Table 10-1 Module Adjustment Example
No. Item
Contents
1 Go to Adjustment mode Issues “Changing to Adjustment mode command” (see Table 9-2) via
I²C^TM I/F.
2 SFP setting
Set R_SFP = 0 to avoid TXFAULT detection at adjustment mode.
3 APC setting
Set R_APC_FB_SET = ”00” and R_APC_FF=11. BIAS and MOD
current is set as “Open Loop”.
4 LD current adjustment Set R_DAC1_GAIN and R_DAC2_GAIN, then adjust
R_APC_FF_DAC1 for modulation current and R_APC_FF_DAC2 for
BIAS current of LD.
5 Duty adjustment
Adjust R_DUTY for 50% duty of LD power, if necessary. After duty
adjustment, tune MOD and BIAS current by R_APC_FF_DAC1 and 2, if
necessary.
6-A PDGAIN adjustment
Adjust R_PDGAIN for PDMON = 1V. Go to step-7.
If you cannot measure PDMON voltage, see step 6-B.
6-B PDGAIN adjustment
Set R_APC_TRGT=100000 and R_PDGAIN=000000 (Gain=23.5dB).
Then set R_APC_FF_SET and R_APC_FB_SET as your configulation.
APC FB adjusts LD output automatically. Adjust R_PDGAIN for
normal LD output. R_APC_TRGT adjustment is for fine tunning of
optical power. Go to step-8.
7 APC FB setting
Set R_APC_TRGT = “10000”.
Set R_APC_FB_SET according to your configuration.
8 APC FB target
adjustment
Adjust R_APC_TRGT to tunning LD output. LD output is adjusted
automaticaaly according to the R_APC_TRGT.
9 Read temperature data Read R_TEMP (on-chip temperature sensor detection temperature).
10 Estimate LD temperature (1) 2 or more temperature adjustment
characteristics
Do step 2 to 8 with different temperature and estimate LD current data of
look-up table.
(2) Single point adjustment
Calculate LD current data of look-up table with on-chip temperature
sensor gain (-1.49℃/LSB), R_TEMP and LD characteristics.
11 Write adjustment data to (1) Make the data for EEPROM.
EEPROM
(2) Issue mode change command to EEPROM.
(3) Write adjustment data to EEPROM.
(4) Read EEPROM data and verify it.
12 Self running mode
Issue mode change command to self-running. AK2573A operates
temperature detection, feed current in response to temperature, and a
feedback operation automatically according to the data in EEPROM.
<MS0189-E-01>
-36-
2004/5