Question there was something wrong with the ALS pin in the Fig 30 of the datasheet. Answer ALS should connect to GND so that bias and modulation current will not be turn off.

Where can I find the user guide for the ADN2871/ADN2873 evaluation boards?

Question Where can I find the user guide for the ADN2871/ADN2873 evaluation boards? Answer Please refer to the attached ADN2871/ADN2873 evaluation board application note.

ADN2871: Differential drive circuit for driving a VCSEL Laser diode.

Q

The ADN2871 laser driver datasheet gives a recommended differential drive
circuit for driving a VCSEL Laser diode. The recommended impedance of the
transmission lines between the driver and laser diode are 20ohm. How critical
is it that these lines are matched to 20ohms. The closest we can get to is
about 30ohm. The data
rates which we are going use is 100Mbps and 1Gbps.

A

I would recommend ADN2873 instead. When the selected TOSA turn on resistance is
only about 15ohm or 10ohm,
the transmission line impedance of about 25 ohm to 30ohm is preferred.
Our solution needs the proper termination at the LDD side. So, a termination
resistor close/matched to the transmission line impedance is preferred. In this
passive termination circuit, the IMOD current high frequency components will be
divided per the termination resistance vs. the laser diode turn on resistance.

Tags: adn2871

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