MAX3737ETJ+T Maxim Integrated Products, MAX3737ETJ+T Datasheet - Page 11

• Manufacturer Part Number: MAX3737ETJ+T
• Description: IC LSR DRVR 2.7GBPS 3.63V 32TQFN
• Manufacturer: Maxim Integrated Products
• Type: Laser Diode Driver (Fiber Optic)r

Specifications of MAX3737ETJ+T

• Data Rate: 2.7Gbps
• Number Of Channels: 1
• Voltage - Supply: 2.97 V ~ 3.63 V
• Current - Supply: 47mA
• Current - Modulation: 85mA
• Current - Bias: 100mA
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 32-WFQFN Exposed Pad
• Mounting Type: Surface Mount
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

100Ω resistor to ground at each monitor output gives the
following relationships:
External sense resistors can be used for high-accuracy
measurement of bias and photodiode currents. On-chip
isolation resistors are included to reduce the number of
components needed to implement this function.
When designing a laser transmitter, the optical output is
usually expressed in terms of average power and
extinction ratio.
helpful in converting between the optical average
power and the modulation current. These relationships
are valid if the mark density and duty cycle of the opti-
cal waveform are 50%.
For a desired laser average optical power (P
optical extinction ratio (r
tion currents can be calculated using the equations in
Table
edge of the laser to monitor transfer (ρ
efficiency (η).
The MAX3737 operates in APC mode at all times. The
bias current is automatically set so average laser power
is determined by the APCSET resistor:
Table 3. Optical Power Relations
Note: Assuming a 50% average input duty cycle and mark density.
Average power
Extinction ratio
Optical power of a 1
Optical power of a zero
Optical amplitude
Laser slope efficiency
Modulation current
Threshold current
Bias current (AC-coupled)
Laser to monitor transfer
Programming the Monitor Diode Current
3. Proper setting of these currents requires knowl-
PARAMETER
V
V
MC_MON
BC_MON
V
PC_MON
Table
______________________________________________________________________________________
P
AVG
= (I
= (I
e
3 gives relationships that are
), the required bias and modula-
Multirate Laser Driver with Extinction
MOD
BIAS
= I
=
Design Procedure
MD
ρ
I
MON
MD
/ 268)
/ 82)
✕
100Ω
✕
✕
100Ω
100Ω
MON
SYMBOL
ρ
P
I
I
P
MOD
BIAS
MON
I
AVG
P
P
r
TH
P-P
η
Set Point
) and slope
e
1
0
AVG
) and
The APCSET pin controls the set point for the monitor-
diode current. An internal current regulator establishes
the APCSET current in the same manner as the MODSET
pin. See the I
Operating Characteristics and select the value of R
SET
The laser driver automatically adjusts the bias to maintain
the constant average power. For DC-coupled laser diodes:
Determine the modulation current from the laser slope
efficiency:
The modulation current of the MAX3737 consists of a
static modulation current (I
to I
portion of I
internal current regulator, which maintains the reference
voltage of V
tor. See to the I
Operating Characteristics and select the value of R
SET
Programming the Modulation Current with
BIAS,
that corresponds to the required current at +25°C:
that corresponds to the required current at +25°C:
and a current proportional to temperature. The
MOD
REF
I
MOD
MD
P
MOD
I
P
across the external programming resis-
P
1
BIAS
set by MODSET is established by an
I
0
MD
I
AVG
= 2P
AVG
η = P
I
= 2P
vs. R
P
MOD
=
RELATION
P
r
P-P
I
=
≥ I
2
e
MD
vs. R
0
= (P
AVG
= P
1
2
at I ≥ I
AVG
TH
=
P-P
×
Ratio Control
= P
= P
/ P
APCSET
I
×
0
BIAS
1
+ I
r
P
/ I
MODS
MODSET
e
AVG
1
P-P
+ P
/ P
/ (r
AVG
R
/ (r
MOD
MOD
- P
η
TH
0
e
APCSET
V
/ η
1
e
0
+
+ 1)
) / 2
REF
+ 1)
I
), a current proportional
/ 2
MOD
×
graph in the Typical
2
graph in the Typical
r
r
e
e
Compensation
+
-
1
1
MOD-
APC-
11