ak2573a AKM Semiconductor, Inc., ak2573a Datasheet - Page 15

• Manufacturer Part Number: ak2573a
• Description: 125m / 156m Laser Diode Driver Apc - Asahi Kasei Microsystems
• Manufacturer: AKM Semiconductor, Inc.

ASAHI KASEI
4.1 APC_FF Function
Fig 4-2 illustrates the APC FF functions. The operation is as follows:
(1) Analog to digital conversion of the voltage (7 bit) that reflects the temperature for every temperature detection
(2) Read the 8 bit current data (address is indicated by the ADC data) from EEPROM and set this value to the
If the current data over temperature is set to each EEPROM address, the compensated current is supplied to the LD
automatically.
To use this function, current data should be stored in EEPROM in advance. The temperature sensor is cover –40# to
115# and EEPROM is prepared with 1.5# steps.
Fig 4-2 APC FF function
4.2 APC_FB Function
Fig 4-3 shows APC_FB functions. It operates as follows:
(1) APC_COMP compares vpd and vapc_ref.
(2) The digital filter calculates the compensation current (R_APC_FB) to equalize vpd with vapc_ref to keep LD
The vapc_ref (RE_APC_TRGT) can be changed over temperature automatically. Temperature compensation
procedure is as same as APC FF (data of DAC_APC is read out EEPROM in response to the temperature).
For the stable operation, the cut-off frequency of RPD and CPD should be 1kHz to 10kHz.
Fig 4-3 APC FB function
<MS0189-E-01>
Monitor
CPD
PD
period (128ms typ).
I-DACs.
power constant.
TEMPSENS
Temperature
RPD
TEMPSENS
charatcteristics
RE_APC_TRGT
PDIN
PDMON
Electrical volume for Monitor PD
TEMPSENS
PDGAIN
Addressing
with
R_TEMP
DAC_APC
(7bit)
ADC
Memory for
Memory for
I-DAC2
vpd
I-DAC1
ADC
vapc_ref
R_TEMP
R_TEMP
Address
512kHz(typ)
COMP
APC_
EEPROM
EEPROM
Data
comp_out
-15-
R_DAC1_FF
R_DAC2_FF
may set initial valuein response to
the temperature at power-on
to accelerate power-up sequence
1/N
APC FF
Digital Filter
I-DAC1
I-DAC2
1/s
MOD Current
BIAS Current
R_APC_FB
Driver
+
R_DACx
[AK2573A]
I-DAC
LD
2004/5