MAX3869EGJ Maxim Integrated Products, MAX3869EGJ Datasheet - Page 8

• Manufacturer Part Number: MAX3869EGJ
• Description: Laser Driver +3.3V, 2.5Gbps SDH-S ONET Laser Driver wi
• Manufacturer: Maxim Integrated Products

Specifications of MAX3869EGJ

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

laser package is used to convert the optical power into
a photocurrent. The APC loop adjusts the laser bias
current so that the monitor current is matched to a ref-
erence current set by R
the APC loop is determined by an external capacitor
(C
ciated with the APC loop-time constant, and to guaran-
tee loop stability, the recommended value for C
0.1µF.
When the APC loop is functioning, the maximum allow-
able bias current is set by an external resistor, R
An APC failure flag (FAIL) is set low when the bias current
can no longer be adjusted to achieve the desired aver-
age optical power. To filter out the APC loop noise, use
+3.3V, 2.5Gbps SDH/SONET Laser Driver
with Current Monitors and APC
Figure 4. Functional Diagram
8
APC
_______________________________________________________________________________________
). To eliminate the pattern-dependent jitter asso-
BIASMON
MOBMON
ENABLE
DATA
CLK
I
I
MAX3869
BIAS
MOD
37
29
MODSET
APCSET
R
D
MODSET
Q
. The time constant of
R
LATCH
BIASMAX
165x
0
1
BIASMAX
MUX
BIASMAX
FAIL
APC
5x
DETECTOR
FAILURE
40x
is
.
C
APC
CAPC
an external capacitor at APCFILT with a recommended
value of 0.1µF.
APC closed-loop operation requires the user to set three
currents with external resistors connected between
ground and BIASMAX, MODSET, and APCSET. Detailed
guidelines for these resistor settings are described in
the Design Procedure section.
If necessary, the MAX3869 is fully operational without
APC. In this case, the laser current is directly set by two
external resistors connected from ground to BIASMAX
and MODSET. See the Design Procedure section for
more details on open-loop operation.
I
MOD
I
MD
APCSET
R
APCSET
I
OUT+
BIAS
OUT-
L
L
BIAS
MD
P2
P1
V
CC
25Ω
R
C
V
P
D
CC
Open-Loop Operation
R
D
1000pF