AK2573A Datasheet, PDF (23/38 Pages) Asahi Kasei Microsystems – 125M / 156M Laser Diode Driver + APC

ASAHI KASEI
[AK2573A]
RE_SFP = 0 operation
Set “H” when OPTALM, CURRALM, TEMPALM or DATAALM is detected
Set “L” when no ALM detected.
RE_SFP=1 operation
Support TX_FAULT of the SFP (Small Form-factor Pluggable) requirement.
Set and hold “H” when detected OPTALM, CURRALM, TEMPALM or DATAALM and go into shutdown
mode.
Reset to “L” when TXDIS1 or TXDIS2 is “H“ → “L”. Refer to “6. Shutdown” for more information.
During “Adjustment mode”, TXFAULT detection is ignored.
6. Shutdown
6.1 Shutdown Operation
Fig6-1showstheshutdownoperation. TheAK2573AsupportstheSFP(SmallForm-factorPluggable)requirement.
Fig 6-1 Shutdown Operation
TXDIS1
TXDIS2
1
X
X
1
0
0
0
0
0
0
RE_SFP
X
X
0
1
1
TXFAULT
X
X
X
0
1
Operation
Shutdown
Shutdown
Normal Operation
Normal Operation
Shutdown
Remarks
Shutdown with pin
Shutdown with pin
SFP TXFAULT
Operation
Fig 6-2 Shutdown Condition
Function
Operation
I-DAC1 / 2 output High-Z (0mA output)
APC_FF
Normal Operation.
APC_FB
ALM
Keep the data at shutdown request.
Normal Operation
TXFAULT
R_SFP=0: Normal Operation
R_SFP=1: Keep the data at shutdown request.
Remarks
6.2 Temperature Comparison between Shutdown Request and Release
The AK2573A keeps the temperature data at shutdown request and compares it with temperature at release request
to avoid over-current conditions at the LD. When the AK2573A detects a temperature difference between at
shutdown request and the release request, the APC FB data is set to 0 or to initial values in response to the
temperature at the release request. The temperature difference is programmable.
WhentheAK2573Adoesnotdetectatemperaturedifference,itkeepstheAPCFBdata,resultingin fasteroperation.
This function works at release request as follows:
if (ABS(R_TEMP_STDW – R_TEMP)) > R_TEMP_WIN)
R_APC_FB = 0 or reset to the initial value in response to the R_TEMP
where, R_TEMP_STDW is a temperature at shutdown request
R_TEMP is a temperature at release request
R_TEMP_WIN is a temperature difference (user programmable)
APC FF continues to operate during shutdown for fast performance when a release request is received. However, the
I-DAC current stays at 0mA.
<MS0189-E-01>
-23-
2004/5