AK2574 Datasheet, PDF (28/30 Pages) Asahi Kasei Microsystems – 156M Laser Diode Driver + APC for Burst Mode

ASAHI KASEI
[AK2574]
7. Module Adjustment Example
Table 7-1 shows the module adjustment example.
Table 7-1 Module Adjustment Example
No. Item
Contents
1 Go to Adjustment mode Issues “Changing to Adjustment mode command” (see Table 5-2) via I²C^TM I/F.
2 Continuous operation
Set BRST=”H” to operate AK2574 as a continuous operation.
3 LD current adjustment Adjust R_DAC1 for modulation current and R_DAC2 for BIAS current of LD.
4 Duty adjustment
Adjust R_DUTY for 50% duty of LD power, if necessary. After duty
adjustment, tune MOD and BIAS current by R_DAC1 and R_DAC2, if
necessary.
5 TXACT adjustment
Adjust LD power by R_DAC1 and R_DAC2 to 3dB down of minimum LD
power that you would like to detect TXACT. Input the burst control signal and
adjust R_DAC_TXACT for tunning TXACT detection time. For more
information, see “3.1 TXACT”.
6 Verification of TXACT
Set R_DAC1 and R_DAC2 back to normal power. Confirm TXACT detection
time.
7 Read temperature data Read R_TEMP (on-chip temperature sensor detection temperature).
8 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.
9 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.
10 Self running mode
Issue mode change command to self-running. AK2574 operates temperature
detection, feed current in response to temperature, and a feedback operation
automatically according to the data in EEPROM.
<MS0266-E-00>
-28-
2003/12