M02066 Datasheet, PDF (11/20 Pages) M/A-COM Technology Solutions, Inc. – 3.3 Volt Laser Driver IC for Applications to 3 Gbps Data Sheet

Functional Description
3.3
Modulator
The M02066 modulation output is optimized for driving a 25Ω load; the minimum required voltage at OUT+ and
OUT- is 0.6V. To interface with the laser diode, a matching resistor (RD) is required for impedance matching. An
RC shunt network is necessary to compensate for the laser diode parasitic inductance, thereby improving the
optical eye.
Typical values are R_SHUNT = 39Ω, C_SHUNT = 3.9 pF.
These values will need to be optimized for a specific laser.Any capacitive loading at the cathode of a laser diode will
degrade the optical output performance. An inductor is used to isolate the BIAS pin from the laser cathode. See
Figure 3-1.
The modulator output stage is designed to drive up to 85mA in either AC-coupled or DC-coupled mode. DC-
coupled performance depends on the laser used.
R_MODSET determines the modulation current according to the following formula: I_MOD = 350/R_MODSET
Figure 3-2 shows the modulation current for a given R_MODSET resistor.
Figure 3-2. Modulation Current vs. R_MODSET
Modulation C urrent in m A
90.00
80.00
70.00
60.00
50.00
40.00
30.00
20.00
10.00
0.00
0
10
20
30
40
Rmodse t (kohms)
02066-DSH-001-D
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Preliminary Information / Mindspeed Proprietary and Confidential