M02061 Datasheet, PDF (25/37 Pages) M/A-COM Technology Solutions, Inc. – 3.3 or 5 Volt Laser Driver

Functional Description
signals may be DC coupled as long as the source of the input signals is operating at a 3.3V supply and the signals
are referenced to VCC3 at the M02061.
3.3.4
Pulse Width Adjust
The data output buffer incorporates pulse-width adjustment control to compensate for laser pulse width distortion.
A potentiometer can be connected between the PWA input and GND for adjustment (programming resistance
should be between 1kΩ and 20kΩ). By adjusting the potentiometer, the pulse-width can be adjusted over a range
of approximately ±40 ps. Pulse width control can be disabled by connecting PWA to V_CC3, resulting in roughly a
50% crossing point at the output and reducing supply current by approximately 1.5mA.
3.3.5
Modulation Control
There are programmable control lines for controlling the modulation current and its temperature compensation.
These inputs can be programmed simply with a resistor to ground.
The modulation current amplitude is controlled by the MOD_SET input pin. The modulation current is temperature
compensated by the TC_SLOPE inputs. The temperature compensation is independent of the setting.
If the temperature compensation at TCSLOPE is disabled, the modulation output current is simply:
IOUT = 100 x (1.3V / R_MODSET)
Where R_MODSET is the resistance from pin MOD_SET to ground.
Figure 3-5 is the most accurate method for selecting RTCslope.
However, you can also select R_TCSLOPE using the following relationship:
R_TCSLOPE = 19.5*(TC)^-1.5, where TC is the desired slope of the modulation current from 25°C to 85°C in%/°C and
R_TCSLOPE is in kΩ. If no temperature compensation is desired, leave R_TCSLOPE open.
In any case, R_TCSLOPE will have negligible effect at M02061 case temperatures below 10°C.
For example:
Given a laser with a desired modulation current at low temperatures of 30mA and a temperature coefficient of -
0.5%/°C at high temperatures (which will require a laser driver temperature coefficient of +0.5%).
Choose R_MODSET = 100 x (1.3V / 30mA) = 4.3kΩ
Choose R_TCSLOPE =19.5*(0.5)^-1.5 kΩ = 56kΩ.
02061-DSH-001-G
Mindspeed Technologies^®
25
Mindspeed Proprietary and Confidential