ASAHI KASEI
[AK2572]
8. Start-Up Setting in SFP Support Mode
8.1 TXFAULT Detection at Power-Up and after Release from Shutdown
8.1.1 OPTALM
In SFP support mode setting (RE_SFP_SET＝”0”), a mask time can be programmed for TXFAULT detection by
OPTALM during the shutdown release so that a time constant delay derived from the external Rpd and Cpd for
detection of the averaged monitor-PD current at the turning-on of LD must be taken into consideration. Block
diagram in Figure 8-1, and pre-settable mask time relation in Table 8-1 are shown.
In the AK2572, the delay time can be shortened by accelerated start-up setting which is made by initial value
setting function of R_APC_FB and so on.
But when OPTALM is selected as one of the TXFAULT target ALMs, and a mask time is set to be shortened, be
noted that LD optical power will not reach the expected level within the mask time and it may be shutdown
through OPTALM detection to TXFAULT control sequence if initial set value of APC_FF or APC_FB is far off.
Figure 8-1 OPTALM Detection Block Diagram
PDGAIN setting
APC Feedback value (R_APC_FB)
APC_
DIGITAL
FILTER
(RE_PDGAIN)
LD
Monitor
PD
COMP
PDIN
vpd
TXFAULT
CONTROL
PDGAIN
OPALM setting
(R_OPTALM)
Cpd
Rpd
vapc_ref
OPTALM
_COMP
APC target
(R_APC_TRGT)
DAC_APC
ATT
A time constant delay at
shutdown release derived
from the external Rpd and
Cpd must be taken into
consideration
OPTALM threshold
(optalm_ref)
Table 8-1 Time to Valid TXFAULT Detection by OPTALM
RE_ RE_TIMER RE_APC_ RE_APC Mask time for TXFAULT
SFP_SET _OPTALM INIT_SET _FF_SET detection by OPTALM
Note
0
1
x
x
0
x
1
x
x
160 ms [Typ.]
160 ms [Typ.]
2 ms [Typ.]
2 ms [Typ.]
0 ms
00, 01, 10
0
1
11
x
x
Accelerated start-up setting
Accelerated start-up setting
Non-support SFP
8.1.2 EXTALM1, EXTALM2
In SFP support mode setting (RE_SFP_SET＝”0”), a mask time can be set for TXFAULT detection by
EXTALM1 and EXTALM2 at the shutdown release.
In Table 8-2, a delay time relation to be set is shown.
Table 8-2 Time to Valid TXFAULT Detection byEXTALM1, EXTALM2
RE_TIMER_EXTALM1
RE_TIMER_EXTALM2
Mask time for TXFAULT detection
by EXTALM1, EXTALM 2
RE_SFP_SET
Note
0
1
X
0 ms
2 ms [Typ.]
0 ms
0
1
Non-support SFP
-30-
< MS0290-E-01>
2004/8
AKM [ ASAHI KASEI MICROSYSTEMS ]
