Datasheet
DS1886
SFP and PON ONU Controller
with Digital LDD Interface
32Maxim Integrated
DS1886 with MAX3710 Operating Modes
The user has the option of selecting among open loop,
APC loop, and dual closed-loop operation modes. These
can be programmed using the DPC_EN and APC_EN
bits in the MAX3710 TXCTRL3 register (Address H0x08),
programmed through A2h Table 02h, Register E6h.
Table 7 indicates what the values in each LUT cor-
responds to in each of the modes. LUT values are not
automatically updated when changing between operat-
ing modes.
Open Loop Mode, DPC_EN = 0, APC_EN = 0
In open loop mode, the laser bias and modulation are
both controlled using LUTs. Each LUT consists of an
8-bit LUT with up to 2NC temperature resolution and an
8-bit offset LUT. This allows the DS1886 to fully support
the 10-bit bias DAC and 9-bit modulation DAC inside the
MAX3710.
APC Loop Mode, DPC_EN = 0, APC_EN = 1
In APC loop or single closed-loop mode, the laser bias
is controlled by an APC loop, while the modulation is
controlled using a temperature-indexed LUT. The APC
setpoint is controlled using an LUT having up to 16NC
resolution. The APC loop initial value (SET_IBIAS) is set
using an LUT having up to 2NC resolution. The modula-
tion LUT consists of an 8-bit LUT with up to 2NC tempera-
ture resolution and an 8-bit offset LUT. This allows the
DS1886 to fully support the 10-bit bias DAC and 9-bit
modulation DAC inside the MAX3710.
Dual Closed-Loop Mode, DPC_EN = 1, APC_EN = 1
In dual closed-loop mode, the laser bias is controlled
by an APC loop, while the modulation is controlled with
an extinction ratio loop. The APC setpoint and extinction
ratio setpoints are controlled using 8-bit LUTs with up to
2NC temperature resolution and 8-bit offset LUTs. Each
loop is initialized using 8-byte LUTs.
Table 7. DS1886 LUT Functions in Open Loop, APC Loop, and Dual Closed-Loop Modes
TABLE REGISTER OPEN LOOP APC LOOP DUAL CLOSED LOOP
04h
80h–A7h 8-Bit Modulation Value [7:0] 8-Bit Modulation Value [7:0] 8-Bit TXCTRL5[7:0]
F0h–F7h IMODMAX[8:1] IMODMAX[8:1] IMODMAX[8:1]
F8h–FFh Modulation Offset [9:2] Modulation Offset [9:2]
SET_IMOD[8:1]
(MOD Initial Value)
06h
80h–A7h 8-Bit BIAS Value [7:0] 8-Bit SET_IBIAS [9:2] 8-Bit SET_IBIAS [9:2]
F0h–F7h IBIASMAX[9:2] IBIASMAX[9:2] IBIASMAX[9:2]
F8h–FFh BIAS Offset [9:2] 8-Bit APC Value [7:0] 8-Bit APC Value [7:0]
08h
F8h–FFh INCBYTE (set to all zeros)
INCBYTE
7:4 = BIASINC
3:0 = MODINC (set to all zeros)
INCBYTE
7:4 = BIASINC
3:0 = MODINC