M02061 Datasheet, PDF (23/37 Pages) M/A-COM Technology Solutions, Inc. – 3.3 or 5 Volt Laser Driver

Functional Description
3.2
Features
• High speed operation; suitable for SFP/SFF applications from 155Mbps to 4.25 Gbps. Typical rise/fall times of
55 ps.
• Programmable temperature compensation. Modulation output and bias output can be controlled using a few
discrete resistors.
• Supports DDMI (SFF-8472) diagnostics when combined with the M02088.
• DC or AC coupled modulation drive. Up to 100mA modulation current available when AC coupled.
• Low overshoot allows high extinction ratio with low jitter.
• Automatic Laser Power Control, with “Slow-Start”.
• Differential data inputs to minimize pattern dependent jitter, PECL and CML compatible.
• Packaged in a QFN24
• 3.3V or 5V operation
3.3
General Description
The M02061 is a highly integrated, programmable laser driver intended for SFP/SFF module with data rates up to
4.25 Gbps. Using differential PECL data inputs, the M02061 supplies the bias and modulation current required to
drive an edge-emitting laser. Monitor outputs and internal safety logic support the DDMI requirements.
The M02061 laser driver consists of the following circuitry: an internal regulator, bias current generator and
automatic power control, data inputs, buffer with pulse width adjust, modulation current control, modulator output,
laser fail indication, disable control, and monitor outputs for the bias current, modulation current, and transmitted
power.
3.3.1
Internal Regulator
The M02061 contains an internal 3.3V regulator so high bit rate performance can be achieved with 5V or 3.3V
power supply.
When operating from a 5V supply (V_CC is connected to +5V), an internal regulator provides a voltage of
approximately 3.3V to the majority of the on-chip circuitry. The on-chip regulator is internally compensated,
requiring no external components. However, for 5V operation with high modulation currents, it may be necessary to
add 12 ohms in series with 100nF to ground at VCC3 or the internal power supply may dip and cause a fault
condition. When a 3.3V supply is used (V_CC and V_CC3 connected to 3.3V) the regulator is switched off and the
internal circuitry is powered directly through the V_CC3 supply pin. The decision as to whether or not the internal
regulator is required is made via the VCC3_SEL pin, which also determines whether the safety circuitry needs to
monitor for proper +5V supply voltage.
For 3.3V applications, SV_CC is sourced from V_CC3 through a switch (leave SV_CC open for 5V applications). SV_CC is
to be used to power the anode of the laser diode and the cathode of the photo diode, any resistive or ferrite pull-ups
on the OUT+ and OUT- outputs should be connected directly to VCC. When a fault condition is present, FAIL will
assert and the switch sourcing SV_CC will open so no current can pass through the laser. SV_CC does not need any
external capacitance, if capacitance to ground is added at SV_CC it should be <100 pF. When SVCC is used, add a
100k Ω pullup resistor to VCC at pin 14 (IBIASout).
For 5V operation, an analog switch controlled by SHTDWNOUT can be used to source 5V to the laser anode. In
the case of a fault condition, SHTDWNOUT will go high and open the analog switch which will result in an open
circuit at the laser. SHTDWNOUT is designed to drive a CMOS logic input. An FET transistor may have excessive
Miller capacitance and a fault may be signalled if it turns on too slow.
02061-DSH-001-G
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