MAX3656(2010) Ver la hoja de datos (PDF) - Maxim Integrated
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componentes Descripción
Fabricante
MAX3656 Datasheet PDF : 15 Pages
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155Mbps to 2.5Gbps Burst-Mode
Laser Driver
Design Example
Select Laser
Select a communication-grade laser for the proper data
rate. Assume the laser output average power is PAVG =
0dBm, the operating temperature is -40°C to +85°C,
and the laser diode has the following characteristics:
wavelength: λ = 1.3µm, threshold current: ITH = 22mA
at +25°C, threshold temperature coefficient: βTH =
1.3%/°C, laser-to-monitor transfer: ρMON = 0.2A/W
(ρMON = ρMONITORDIODE x LLASER-TO-MONITORDIODE),
and laser slope efficiency: η = 0.05mW/mA at +25°C.
Determining RAPCSET
The desired monitor diode current is estimated by IMD =
PAVG ✕ ρMON = 200µA. The IMD vs. RAPCSET graph in the
Typical Operating Characteristics shows RAPCSET at 12kΩ.
Determining RMODSET
Assuming re = 10 and an average power of 0dBm (1mW),
the peak-to-peak optical power PP-P = 1.64mW (Table 1).
The required modulation current is 1.64(mW)/0.05(mW/mA)
= 32.8mA. The IMOD vs. RMODSET graph in the Typical
Operating Characteristics shows RMODSET at 9kΩ.
Determining RBIASMAX
Determine the maximum threshold current (ITH(MAX)) at
TA = +85°C and end of life. Assuming (ITH(MAX)) =
50mA, the maximum bias current should be:
IBIASMAX = ITH(MAX)
In this example, IBIASMAX = 50mA. The IBIASMAX
vs. RBIASMAX graph in the Typical Operating Charact-
eristics shows RBIASMAX at 8kΩ.
ZO = 50Ω
ZO = 50Ω
ZO = 50Ω
ZO = 50Ω
VCC
130Ω
IN+
82Ω VCC
130Ω
MAX3656
IN-
82Ω
VCC
130Ω
82Ω VCC
BEN+
130Ω
BEN-
82Ω
ZO = 50Ω
ZO = 50Ω
100Ω
ZO = 50Ω
ZO = 50Ω
100Ω
IN+
IN-
MAX3656
BEN+
BEN-
Figure 5. Connecting to CML Outputs
VCMBEN + (100mV to 800mV)
VCMBEN
VCMBEN - (100mV to 800mV)
3.3V
R1 = 1.65kΩ
VCMBEN = +2.0V
R2 = 2.54kΩ
IN+
IN-
BEN+
BEN-
MAX3656
Figure 4. Connecting to PECL Outputs
Figure 6. Single-Ended Biasing for Burst Enable
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