M02061 Datasheet, PDF (27/37 Pages) M/A-COM Technology Solutions, Inc. – 3.3 or 5 Volt Laser Driver

Functional Description
When DC coupled, OUT+ should be connected through a series resistor to the laser such that the total impedance
seen at the output is 25 ohms. This will result in the optimum pulse response while allowing the maximum
modulation current (see Figure 4-2).
The output can also be AC coupled to the laser. This is the required operating mode when using a 3.3V supply
(unless the laser has a small forward voltage and OUT+ will not go below 1.6V). When AC coupled the dynamic
resistance seen by OUT+ should still be 25 ohms. In addition to a resistor in series with the laser, a capacitor is
added in series and a ferrite is used to pull up the collector at OUT+ to V_CC.
When the laser is AC coupled, the OUT- pin is usually tied to the laser anode through an AC coupled series resistor
which matches the impedance seen by the OUT+ pad (see Figure 4-1).
The output stage also has a separate current path to GND labelled GND₀. This isolates the output switching
currents from the rest of the system.
Figure 3-6. Modulator Output
0.75 nH ^* _OUT-
0.4pF
0.75 nH ^*
OUT+
For V_CC =5V, OUT+ and OUT-
should not be driven below 1.15V
For V_CC = 3.3V, OUT+ and OUT-
should not be driven below 1.6V.
GND_A
(optional
external
inductance)
* Denotes bond
wire internal to
MLF package
3.3.7
Fail Output
The M02061 has a FAIL alarm output which is compatible with the TX_FAULT signalling requirements of common
pluggable module standards.
The ESD protection on this pin provides a true open collector output that can withstand significant variation in V_CC
when signalling between circuit boards. Also, if the M02061 loses power the pull-up will signal a fail condition. In a
simple static protection scheme used by other ICs the protection diodes would clamp the FAIL signal to ground
when the chip loses power.
02061-DSH-001-G
Mindspeed Technologies^®
27
Mindspeed Proprietary and Confidential