MAX3669ETG+ Maxim Integrated Products, MAX3669ETG+ Datasheet - Page 10

• Manufacturer Part Number: MAX3669ETG+
• Description: IC LASR DRVR 622MBPS 5.5V 24TQFN
• Manufacturer: Maxim Integrated Products
• Type: Laser Diode Driver (Fiber Optic)r

Specifications of MAX3669ETG+

• Data Rate: 622Mbps
• Number Of Channels: 1
• Voltage - Supply: 3.14 V ~ 5.5 V
• Current - Supply: 40mA
• Current - Modulation: 75mA
• Current - Bias: 80mA
• 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

+3.3V, 622Mbps SDH/SONET
Laser Driver with Current Monitors and APC
The total power dissipation of the MAX3669 can be esti-
mated by the following:
where I
MAX
cal laser forward voltage.
The following is an example of how to set up the
MAX3669.
A communication-grade laser should be selected for
622Mbps applications. Assume the laser output aver-
age power is P
ratio is r
-40°C to +85°C, and the laser diode has the following
characteristics:
The desired monitor diode current is estimated by
I
vs. APC Set Resistor graph in the Typical Operating
Characteristics shows that R
To achieve a minimum extinction ratio (r
temperature and lifetime, calculate the required extinc-
tion ratio at +25°C. Assuming r
optical power P
The required modulation current is 1.81(mW) /
0.05(mW/mA) = 36.2mA. The Modulation Current vs.
Modulation Set Resistor graph (see Typical Operating
Characteristics) shows that R
Calculate the maximum threshold current (I
T
50mA, the maximum bias current should be:
10
MD
A
Wavelength:
Threshold Current:
Threshold Temperature
Coefficient:
Laser to Monitor Transfer:
Laser Slope Efficiency:
= +85°C and end of life. Assuming I
, I
= P
______________________________________________________________________________________
MOD
BIAS
AVG x
e
= 6.6 (8.2dB), the operating temperature is
P = V
is the modulation current, and V
is the maximum bias current set by R
+ I
ρ
I
BIAS
MON
MOD
Applications Information
AVG
Calculate Power Consumption
p-p
CC x
= I
= 200µA. The Monitor Diode Current
= 1.81mW, according to Table 1.
(V
= 0dBm, the minimum extinction
I
CC
TH(MAX)
CC
+ (V
- 20Ω
APCSET
MODSET
Determine R
Determine R
CC
Determine R
e
+ I
x
λ = 1.3µm
Ι
β
ρ
η = 0.05mW/mA
at +25°C
= 20, the peak-to-peak
- V
TH
TH
MON
MOD
I
MOD
should be 6kΩ.
f
= 22mA at +25°C
)
= 1.3%/°C
should be 5kΩ.
x
= 0.2A/W
/ 2
Select Laser
I
/ 2)
e
BIAS
) of 6.6dB over
f
TH(MAX)
TH(MAX)
BIASMAX
is the typi-
MODSET
APCSET
BIAS-
) at
=
In this example, I
Maximum Bias Set Resistor graph in the Typical
Operating Characteristics shows that R
be 3kΩ.
To avoid saturating the current mirror of BIASMON, the
voltage at this pin should not drop below (V
The resulting condition is:
where I
the application.
To avoid saturating the current mirror of MODMON, the
voltage at this pin should not drop below (V
The resulting condition is:
To drive modulation currents greater than 50mA at
3.3V, external pullup inductors (Figure 5) should be
used to DC-bias the modulation output at V
configuration isolates the laser forward voltage from the
output circuitry and allows the output at OUT+ to swing
above and below the supply voltage V
Figure 5. Output Termination for Maximum Modulation Current
MAX3669
Modulation Currents Exceeding 50mA
BIASMAX
R
MODMON
R
OUT+
OUT-
BIAS
MD
BIASMON
10Ω
is the maximum current expected for
V
BIAS
CC
≤
= 68.1mA. The Bias Current vs.
≤
FERRITE BEAD
1V
1.6V
⎛
⎜
⎝
Determine R
Determine R
A
I
FERRITE
BEADS
MOD
MOD
⎛
⎜
⎝
I
1µF
BIASMAX
C
D
A
BIAS
⎞
⎟
⎠
5Ω
R
D
CC
BIASMAX
100pF
.
⎞
⎟
⎠
LD
BIASMON
MODMON
CC
CC
CC
. Such a
- 1.6V).
should
- 1V).
R
FILT
C
FILT