F0513005L Datasheet, PDF (11/13 Pages) Eudyna Devices Inc – 3 Gb/s NRZ Data Rate Laser Diode Driver

3 Gb/s Laser Diode Driver
F0513005L
♦ General Description
Bias current and modulation current are very important electrical characteristics in a la-
ser diode. A center value of the driving current of a laser diode is bias current, which is
designed to be presettable ranging from 1 to 50 mA by a controlled voltage of V_B terminal
according to the threshold current of an employed laser diode and the application. An optical
output power is proportional to an amplitude of the driving current of a laser diode called
modulation current which can be controlled from 1 to 50 mA by a voltage of V_M terminal.
Protection against laser thermal runaway is provided by auto power control. V_APC terminal is
used to control the bias current setting negative feedback, monitoring the optical output
power by PIN photo diode.
♦ Positive Temperature Characteristics
The most remarkable feature of the F0513005L, which can not be found in other IC's, is
the positive temperature characteristics of the modulation current designed to be +0.5 %/°C.
Emission efficiency in typical laser diodes exhibits negative temperature characteristics;
their optical output decreases with increasing ambient temperature. In the case of multi-
quantum well (MQW) laser diodes, which is the focus of keen interest, the temperature coef-
ficient of -0.5 %/°C is reported. The F0513005L can successfully compensate the tempera-
ture fluctuation of the optical output power, providing a stable extinction ratio. If a driver
circuit does not have a positive temperature characteristic in the modulation current, the bias
current increases above the threshold current at higher temperature, resulting in degradation
of the extinction ratio. It is not impossible to achieve this kind of compensation by external
circuits; it is, however, unrealistic owing to inevitably troublesome tuning.
♦ User-friendly Design
The F0513005L features a user-friendly design for system designers, permitting a single
+5 V power supply operation. A differential ECL compatible input for direct control from ECL
or conventional GaAs logic IC's is provided. Two unique auto power controls (V_APC1, V_APC2)
permit modulation of the bias current control setting as a mechanism to protect the laser
diode against thermal runaway. The APC controls may be modulated at rates up to 100
MHz.