AK2573A Datasheet, PDF (24/38 Pages) Asahi Kasei Microsystems – 125M / 156M Laser Diode Driver + APC

ASAHI KASEI
Table 6-3 Operation at shutdown release
RE_SFP TXFAULT at
RE_TEMP_
Shutdown request DET
0
X
0
0
X
1
0
X
1
1
0
0
1
0
1
1
0
1
1
1
X
Temp Difference
result
X
0
1
X
0
1
X
R_APC_FB
Initial value
Hold data
Initial value
Initial value
Hold data
Initial value
Initial value
[AK2573A]
Remark
7. Power-up / down Timing
7.1 Delay Time of TXFAULT Detection with OPTALM
In correspond to the delay time caused by RPD and CPD to get the moniter PD average current, the delay time of
TXFAULT detection with OPTALM is set when RE_SFP=”1” (SFP support). AK2573A has 2 delay time when
RE_SFP=”1”: normal delay and accelerated delay. Accelerated delay may be selected when both I-DAC1 and I-DAC2
are set to APC_FF or APC_FB with an initial value setting.
Table 7-1 shows the delay time of TXFAULT detection with OPTALM and Fig 7-1 illustrated block diagram.
Note: When accelerated delay is selected with RE_SFP=”1”, APC_FF data or initial data of APC_FB should be
suitable, otherwise AK2573A might go into shutdown by detection of OPTALM after delay time.
Fig 7-1 APC_FB Block Diagram
LD
CPD
Monitor
PD
RPD
PDGAIN
(R_PDGAIN)
PDIN
PDGAIN
vpd
APC_
COMP
Digital
Filter
OPTALM Level
(R_OPTALM)
Detection and reset OPTALM
vary with the cut-off
frequency of CPD and RPD
APC Terget
(R_APC_TRGT
)
DAC_APC
vapc_ref
ATT
OPTALM
reference
(opalm_ref)
APC Feedback
(R_APC_FB)
OPTALM
TX_FAULT
Control
Table 7-1 Delay time of TXFAULT detection with OPTALM
RE_SFP R_TIMER_ R_APC_ R_APC_ Delay Time of TXFAULT Remarks
OPTALM INIT_SET FF_SET detection with OPTALM
0
X
X
X
0 ms
disable TXFAULT
detection
1
0
X
X
160 ms (typ)
1
1
0
00
160 ms (typ)
01
10
1
1
1
1
X
11
2 ms (typ)
1
X
2 ms (typ)
Acceleration
power-up
<MS0189-E-01>
-24-
2004/5