M02068_17 Datasheet, PDF (12/18 Pages) M/A-COM Technology Solutions, Inc. – 3.3 Volt Laser Driver IC for 155/622 Mbps

Functional Description
3.5
Enable Control
The CX02068 incorporates a dual polarity laser driver enable function. When ENA is LOW or DIS is HIGH, both
the bias and modulation currents are off.
3.6
Current Monitors
The CX02068 features bias and modulation current monitor outputs. The BIAS_MON output sinks a current equal to
nominally 1/55 of the laser bias current (I_BIAS). The MOD_MON output sinks a current equal to nominally 1/55 of the
laser modulation current (I_MOD). BIAS_MON and MOD_MON should be connected through a pull-up resistor to V_CC.
Choose a pull-up resistor value that ensures a voltage at BIAS_MON greater than V_CC -1.6 V and a voltage at
MOD_MON greater than V_CC -1.0 V. These pins should be tied to V_CC if not used.
3.7
Slow-Start
For laser safety and reliability, the CX02068 incorporates a slow-start circuit that provides a delay of approximately
200 ns before enabling the laser diode.
3.8
Temperature Compensation
The CX02068 features built in temperature compensation of the modulation current set using external resistors.
Current pulled from TC_SLOPE adjusts the slope of the temperature compensation where as current pulled from
TC_START sets the threshold temperature for the coefficient.
02068-DSH-001-C
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