AK2573A Datasheet, PDF (14/38 Pages) Asahi Kasei Microsystems – 125M / 156M Laser Diode Driver + APC

ASAHI KASEI
[AK2573A]
3.2 Duty Adjustment
AK2573A supplies a programmed duty adjustment in response to the temperature from an on-chip temperature
sensor (every 6℃, Duty data is stored in E_DUTY_TC, see Table 8-3 for more information). Write same data into
E_DUTY_TC for constant duty adjustment. Table 3-3 and 3-4 show the characteristics of duty adjustment function.
Table 3-3 Duty Adjustment characteristics
Item
Symbol min
typ
max Unit
Remarks
Maximum Pulse Extended
Td
0.5
ns Note 1
1 LSB Pulse Extended Step Tstep
0.03
ns 32 Steps
Pulse Extended Stability
Tsta
0.2
ns Ta=-40 to 85℃, VDD=3.1～
3.5V, 0.3ns Extended (Note 1)
Note 1: This parameter is characterized and is not 100% tested.
Table 3-4 Pulse Extended
R_DUTY Pulse Extended (typ) [ns]
0
0
1
0.03
2
0.06
.
.
.
.
30
0.90
31
0.93
Remark
4. APC
The AK2573A has two APC functions, APC FF (Feed-forward) and APC FB (Feedback).
APC FF supplies a programmed current in response to the temperature from an on-chip temperature sensor.
APC_FB provides stable a power control function using a digital feedback algorithm. The APC_FF and APC_FB is
user programmable. Fig4-1 illustrates APC block diagram.
Fig 4-1 APC Block Diagram
Monitor
PD
CPD
RE_TEMP_OFFSET
TEMPSN
S
TEMPMON
PDMON
RPD
PDGAIN
(RE_PDGAIN)
PDIN
PDGAIN vpd
APC Target
(RE_APC_TRGT)
DAC_APC
Temperature ALM
(RE_TEMPALM)
ALM Polarity
(RE_ALM_POL)
TEMP
ALM
ADC
APC FF
(R_DAC1_FF)
R_TEMP ^EEPROM
APC Operation
(RE_APC_FF_SET)
K_DAC1
_FBRT
APC FB Operation
(RE_APC_FB_SET)
K_DAC2
_FBRT
APC FB Initial setting
(RE_APC_INIT_SET)
APC FF
(R_DAC2_FF)
APC Feedback
(R_APC_FB)
apc_comp_out
APC_
COMP
Digital Filter
1/N
1/s
OPTALM
(RE_OPTALM_)
vapc_ref
ATT
OPTALM Reference
(optalm_ref)
TEMPALM
Gain
(RE_DAC1_GAIN)
R_DAC1
Imod _Driver
+
I-DAC1
IMOD
IMODN
I-DAC1 FB
(R_DAC1_FB)
* 0.0095
Gain
I-DAC2 FB _{(RE_DAC2_GAIN)}
(R_DAC2_FB)
MODMO
N
+
R_DAC2
I-DAC2
Ibias IBIAS
ALMPolarity
(RE_ALM_POL)
* 0.0095
BIASMON
R_DAC1
R_DAC2
CURR
ALM
CURRALM
Over current ALM
(RE_CURRALM)
ALM Polarity
(RE_ALM_POL)
OPTALM
OPTALM
<MS0189-E-01>
-14-
2004/5