AK2572 Datasheet, PDF (13/50 Pages) Asahi Kasei Microsystems – APC for Burst Mode Applicable Direct Modulation Laser Diode

ASAHI KASEI
[AK2572]
3. I-DAC, V-DAC Functional Part
The AK2572 equips Current source type I-DAC1 (Max. sourcing current＝10.2 mA [Typ.]) and Voltage output
type V-DAC3 (Max. output voltage＝2.2 V [Typ.]) for the LD modulation current setting, and Current sink type
I-DAC2 (Max. sink current＝85.0 mA [Typ.] ) for the bias current setting. Selection of enable / disable each DAC
is set by RE_DAC_SET. Output current of I-DAC1 (Max. value＝10.2 mA / 1.02 mA [Typ.]) and I-DAC2 (Max.
value＝85.0 mA / 42.5 mA [Typ.]), and output voltage of V-DAC3 (Max. value＝2.2 V / 1.2 V [Typ.]) can be
switched by gain setting. This gain switching allows to lower current consumption and to improve the accuracy
per 1 LSB. In Tables 3-1 ~ 3-3, the characteristics of I-DAC2, I-DAC1 and V-DAC3 are shown.
I-DAC2 directly sets the LD bias current. A current multiplied by a factor of 0.012 [Typ.] of I-DAC2 set value is
output (Current source) on BIASMON-pin.
Table 3-1 I-DAC2 characteristics (I-DAC2 is set “Enabled” / “Disabled” by RE_DAC_SET [1]＝“1” / “0”)
RE_DAC2_GAIN Gain Max. output current (Code＝FFh)［Typ］ Range ［Typ］ Current/step ［Typ］
1
1
85.0 mA
0 ~ 85.0 mA
333 μA
0
1/2
42.5 mA
0 ~ 42.5 mA
167 μA
[Note] I-DAC2 characteristics : Resolution＝8 bits, DNL＝±1 LSB (DAC code＝10h ~ FFh)
Output current variation at Maximum DAC code (FFh)＝Typ.±8 %
Temperature compensation data (Retained in EEPROM), which are set for I-DAC1 and V-DAC3, can be
selected by RE_MODV_SEL setting as shown in Table 3-4.
When E_MOD_TC (128 address locations) is assigned as the setting data, I-DAC1(RE_MODV_SEL＝“0”)
generates a reference current of the modulation current to external Laser Diode Driver (LDD), and V-DAC3
(RE_MODV_SEL＝“1”) generates a reference voltage of the Modulation current to external LDD. A voltage
driver type LDD can also be adopted by converting an I-DAC1 output current to a voltage by external
resistors or by using V-DAC3 output voltage. When E_EXTRA_TC (32 address locations) is assigned as the
setting data, I-DAC1 output (RE_MODV_SEL＝“1”) or V-DAC3 output (RE_MODV_SEL＝“0”) can be used
as APD control voltage or LDD reference voltage etc.. When temperature compensation by E_EXTRA_TC is
not required, same data should be written at all address locations.
Table 3-2 I-DAC1 characteristics (I-DAC1 is set “Enabled” / “Disabled” by RE_DAC_SET [0]＝“1” / “0”)
RE_DAC1_GAIN Gain Max. output current (Code＝FFh)［Typ］ Range ［Typ］ Current / step［Typ］
1
1
10 .2 mA
0 ~ 10 .2 mA
40 μA
0
1/10
1.02 mA
0 ~ 1.02 mA
4 μA
[Note] I-DAC1 characteristics : Resolution＝8 bits, DNL＝±1 LSB (DAC code＝10h ~ FFh)
Output current variation at Maximum DAC code (FFh)＝Typ.±8 %
Table 3-3 V-DAC3 characteristics (V-DAC3 is set “Enabled” / “Disabled” by RE_DAC_SET [2]＝“1” / “0”)
RE_DAC3_GAIN Gain Max. output voltage (Code＝FFh)［Typ］ Range ［Typ］ Voltage / step［Typ］
1
1.2 / 2.2
1.2 V
0 ~ 1.2 V
4.7 mV
0
1
2.2 V
0 ~ 2.2 V
8.6 mV
[Note] V-DAC3characteristics : Resolution＝8 bits, DNL＝±1 LSB (DAC code＝20h ~ FFh)
Output voltage variation at Maximum DAC code (FFh)＝Typ.±8 %
Table 3-4 RE_MODV_SEL setting
RE_MODV_SEL
I-DAC1
V-DAC3
0
E_MOD_TC
E_EXTRA_TC
1
E_EXTRA_TC
E_MOD_TC
[Note] Although E_MOD_TC has 128 address locations and E_EXTRA_TC has 32 address locations,
temperature resolution of each temperature compensation data is 0.75 ℃ [typ.] because of the
temperature compensation data is derived from a linear interpolation method (Refer to Section 4.1).
-13-
<MS0290-E-01>
2004/8