DS1875T+ Maxim Integrated Products, DS1875T+ Datasheet - Page 17

• Manufacturer Part Number: DS1875T+
• Description: IC SFP CTRLR/TRIPLEXER 38-TQFN
• Manufacturer: Maxim Integrated Products

Specifications of DS1875T+

• Applications: Fiber Optics
• Interface: I²C
• Voltage - Supply: 2.85 V ~ 3.9 V
• Package / Case: *
• Mounting Type: Surface Mount
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

When using autodetect mode or closed-loop mode,
BEN should be equal to V
mode, BEN should be ground or any burst length.
The MOD output is an 8-bit scaleable voltage output
that interfaces with the MAX3643’s VMSET input. An
external resistor to ground from the MAX3643’s
MODSET pin sets the maximum current that the voltage
at the VMSET input can produce for a given output
range. This resistor value should be chosen to produce
the maximum modulation current the laser type requires
over temperature. Then the MOD output’s scaling is
used to calibrate the full-scale (FS) modulation output
to a particular laser’s requirements. This allows the
application to take full advantage of the MOD output’s
resolution. The modulation LUT can be programmed in
2°C increments over the -40°C to +102°C range.
Ranging of the MOD DAC is possible by programming
a single byte in Table 02h, Register 8Bh.
Figure 1. Power-Up Timing (BEN is a Long Burst)
SAMPLE
V
BIAS
I
MOD
V
BIAS
CC
______________________________________________________________________________________
CC
V
BIAS LUT
POA
VALUE
or long burst. In open-loop
t
INIT
Modulation Control
PON Triplexer and SFP Controller
1
DC Operation
2
3
4
5
On power-up the modulation and bias outputs remain off
until V
been completed, and, if the V
a V
alarm level must clear the V
these conditions (t
enabled with the value determined by the temperature
conversion and the modulation LUT (Table 04h).
When the MOD output is enabled, the BIAS output is
turned on to a value equal to the temperature-indexed
value in the BIAS LUT (Table 08h). Next, the APC inte-
grator is enabled, and single LSB steps are taken to
tightly control the average power.
If a fault is detected and TX-D is toggled to re-enable
the outputs, the DS1875 powers up following a similar
sequence to an initial power-up. The only difference is
that the DS1875 already determined the present tem-
perature, so the t
DS1875 to recall the APC and MOD set points from
EEPROM.
CC
6
BIAS and MOD Output During Power-Up
APC INTEGRATOR ON
CC
conversion above the customer-defined V
7
is above V
8
INIT
9
INIT
POA
) are satisfied, the MOD output is
10
, a temperature conversion has
time is not required for the
CC
11
CC
low alarm (t
ADC alarm is enabled,
12
13
INIT
). Once all
CC
low
17