AK2572 Datasheet, PDF (25/50 Pages) Asahi Kasei Microsystems – APC for Burst Mode Applicable Direct Modulation Laser Diode

ASAHI KASEI
[AK2572]
5. Burst Mode Operation
The AK2572 is put into Burst mode support operation by setting RE_BURST_SET＝“1”.
When the Burst mode operation is enabled, do not use APC_FB function. Control the LD current by APC_FF
function only (RE_APC_FF_SET＝“3”, RE_APC_FB_SET＝“0”), and OPTALM and CURRALM should not
be selected as the target alarm on TXFAULT-pin (RE_OPTALM_SET＝“0”, RE_CURRALM_SET＝“0”).
Figure 5-1 Burst Mode Operation
Burst ON (Active)
Burst OFF (Inactive)
Burst Signal (BURST-pin)
I-DAC1, I-DAC2, V-DAC3
Temperature Detection
APC_FF Operation
R_DACx (x=1~3)
EXTALM1
EXTALM2
TEMPALM
ON (Output Current / Voltage)
ON
ON (Update Data)
Hold Data
61ns [typ]
ON/OFF
ON
ON
ON (Output Current / Voltage)
ON
ON (Update Data)
Update Data
ON
ON
(1) Alarm mask function
EXTALM1 and EXTALM2 can be masked for 61 ns [Typ.] at the rising edge of Burst signal by
RE_BURST_ALM setting. By enabling this masking operation, EXTALM1 and EXTALM2 for
TXFAULT-pin output (Logical “OR” function of alarms set by EEPROM / Register) is masked but output to
status register R_TXFLT_ST is not masked and ALM detect result is always retained in that register.
(2) APC operation masking function
Updating APC_FF data (R_BIAS_FF, R_MOD_FF) and temperature detection by the On-chip temperature
sensor are always executed. DAC setting data (R_DACx [x＝1~3]) are updated during the Burst OFF.
During the Burst ON, DAC setting data are not updated but the updated data made during the previous
Burst OFF period is held.
5. 1 Power Leveling ï¼»1ï¼½
In Power Leveling [1] mode, the data to be loaded to register (R_MOD_FF) from one of two patterns of the
Modulation current temperature compensation data which are retained in EEPROM is selected by Hardware
pin control (MOD_CTRL-pin) and it can be used as APC_FF data.
EXTALM2 / MOD_CTRL-pin becomes MOD_CTRL control pin when both RE_PWR_LVL1_SET and
RE_SFP_SET are set to “1”, and Power Leveling [1] function is available. EEPROM data is set to each DAC by
MOD_CTRL-pin as shown in Table 5-1.
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< MS0290-E-01>
2004/8