MAX3656ETG+T Maxim Integrated Products, MAX3656ETG+T Datasheet - Page 11

IC LASR DRVR 2.5GBPS 3.6V 24TQFN

MAX3656ETG+T

Manufacturer Part Number
MAX3656ETG+T
Description
IC LASR DRVR 2.5GBPS 3.6V 24TQFN
Manufacturer
Maxim Integrated Products
Type
Laser Diode Driver (Fiber Optic)r
Datasheet

Specifications of MAX3656ETG+T

Data Rate
2.5Gbps
Number Of Channels
1
Voltage - Supply
3 V ~ 3.6 V
Current - Supply
40mA
Current - Modulation
85mA
Current - Bias
70mA
Operating Temperature
-40°C ~ 85°C
Package / Case
24-TQFN Exposed Pad
Mounting Type
Surface Mount
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Other names
MAX3656ETG+T
MAX3656ETG+TTR
When using the MAX3656’s APC feature, program the
average optical power by adjusting the APCSET resis-
tor. To select this resistor, determine the desired moni-
tor current to be maintained over temperature and
lifetime. See the I
Operating Characteristics and select the value of
R
Set the LONGB pin according to Table 2 to optimize
APC loop operation.
The laser modulation current output OUT+ is optimized
to drive a 15Ω load and must be DC-coupled. A series
damping resistor, R
the laser diode. The combined value of the series
damping resistor and the laser diode equivalent series
resistance should be close to 15Ω. An RC shunt com-
pensation network, R
the laser diode cathode and ground should be provided
to reduce optical output aberrations and duty-cycle dis-
tortion caused by laser diode parasitic inductance. The
values of R
the laser diode and PC board layout characteristics for
optimal optical eye performance (refer to Application
Note 274: HFAN-02.0: Interfacing Maxim’s Laser Drivers
with Laser Diodes ). The OUT- pin is connected through
a 15Ω resistor and switching diode to the laser diode
anode. The switching diode at OUT- improves the opti-
cal output eye and burst-enable delay by better match-
ing the laser diode characteristics.
For data rates greater than 1Gbps, a parallel RL peak-
ing network, R
anode and V
a differential drive for the laser diode to improve
rise/fall times and reduce jitter. The values of R
L
board layout characteristics for optimal optical eye
performance.
Current in the BIAS output switches at high speed
when bursting; therefore, the BIAS+ pin should be con-
nected directly through a resistor, equal to R
determined above, to the laser diode cathode. The
Table 2. Setting the LONGB Input Pin
P
APCSET
are also adjusted to match the laser diode and PC
LONGB
0 or 1
0
1
that corresponds to the required current.
COMP
CC
P
/L
is recommended. This network creates
Interfacing with Laser Diodes
and C
P
MD
______________________________________________________________________________________
, connected between the laser diode
Setting the LONGB Input Pin
D
Programming the APC Loop
COMP
, provides impedance matching to
vs. R
COMP
continuous mode operation
/C
Burst on-time >1.2µs or
Data rates of 155Mbps
APCSET
Burst on-time ≤1.2µs
COMP
can be adjusted to match
CONDITION
, connected between
graph in the Typical
155Mbps to 2.5Gbps Burst-Mode
P
D
and
as
BIAS- pin is connected through a 10Ω resistor and
switching diode to V
The MAX3656 data and BEN inputs are internally biased.
Although the inputs are compatible with LVPECL signals,
it is not necessary to drive the MAX3656 with a standard
LVPECL signal. While DC-coupled, the MAX3656 oper-
ates properly as long as the specified common-mode
voltage and differential voltage swings are met.
Because of the on-chip biasing network (Figure 3), the
MAX3656 inputs self-bias to the proper operating point
to accommodate AC-coupling.
See Figures 4 and 5 for connecting to PECL or CML
data outputs.
Figure 3. MAX3656 Internal Biasing
BEN+
BEN-
IN+
IN-
V
V
V
V
CC
CC
CC
CC
Input Termination Requirements
5kΩ
5kΩ
5kΩ
5kΩ
CC
V
V
CC
CC
.
16kΩ
24kΩ
16kΩ
24kΩ
Laser Driver
MAX3656
V
V
CC
CC
11

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