Datasheet

DS1886
SFP and PON ONU Controller
with Digital LDD Interface
34Maxim Integrated
The offsets are also temperature indexed. Figure 16 illus-
trates how the offsets would affect the final output as the
temperature varies.
Table 10 shows the temperature resolution for the offsets.
MODULATION Value
Figure 17 shows how to calculate the MODULATION value
that is recalled from the LUT and sent to the MAX3710.
BIAS Value
Figure 18 shows how to calculate the BIAS value that is
recalled from the LUT and sent to the MAX3710.
Figure 16. Offset LUT
Figure 17. MODULATION LUT (Open Loop and APC Mode) Figure 18. BIAS LUT (Open Loop)
Table 10. Temperature Resolution for Offsets
ROW BYTE 0 BYTE 1 BYTE 2 BYTE 3 BYTE 4 BYTE 5 BYTE 6 BYTE 7
F8h
-40NC -8NC +8NC +24NC +40NC +56NC +72NC +88NC
9
MOD OFFSET[9:2]
DS1886
MODULATION VALUE
POW_LEV
[1:0]
8 7 6 5 4 3 2
1
MOD[7:0]
07 6 5 4 3 2
MAX3710
SET_IMOD[8:0]
GAIN
POWER
LEVEL (dB)
00 1*0
01 0.5-3
1X 0.25-6
KRMD[2:1]
(MAX3710)
1X
01
00
TXCTRL3
1X
01
00
0
255
511
VALUE DETERMINED BY LUTs WITH CORRESPONDING
OFFSET LUTs
767
1023
EACH OFFSET REGISTER CAN BE INDEPENDENTLY SET BETWEEN
0 AND 1020. 1020 = 4 x FFh. THIS EXAMPLE ILLUSTRATES POSITIVE
AND NEGATVE TEMPCO.
LUT
BITS
7:0
F8h
LUT
BITS
7:0
F9h
LUT
BITS
7:0
FAh
LUT
BITS
7:0
FBh
LUT
BITS
7:0
FCh
LUT
BITS
7:0
FDh
LUT
BITS
7:0
FEh
LUT
BITS
7:0
FFh
0
255
511
-40°C -8°C +8°C +24°C +40°C
OFFSET LUTs [8 REGISTERS] OFFSET LUTs [8 REGISTERS]
+56°C +72°C +88°C +104°C
VALUE DETERMINED BY LUTs WITH CORRESPONDING
OFFSET LUTs
767
1023
EACH OFFSET REGISTER CAN BE INDEPENDENTLY
SET BETWEEN 0 AND 1020. 1020 = 4 x FFh. THIS
EXAMPLE ILLUSTRATES POSITIVE TEMPCO.
LUT
BITS
7:0
F8h
LUT
BITS
7:0
F9h
LUT
BITS
7:0
FAh
LUT
BITS
7:0
FBh
LUT
BITS
7:0
FCh
LUT
BITS
7:0
FDh
LUT
BITS
7:0
FEh
LUT
BITS
7:0
FFh
-40°C -8°C +8°C +24°C +40°C +56°C +72°C +88°C +104°C
9
BIAS OFFSET[9:2]
THE BIAS VALUE THAT IS RECALLED FROM THE LUT AND SENT TO THE MAX3710
IS CALCULATED AS FOLLOWS:
8 7 6 5 4 3 2
1
BIAS[7:0]
07 6 5 4 3 2
MAX3710
SET_IBIAS[9:0]