980 nm laser Specs

[Vizier87]

Hi dudes,
I recently acquired this product for my fibre optics circuit. However, the specs are quite vague to me. From the datasheet:

**broken link removed**

So I suppose the Forward voltage can be as much as it needs, only that is follows the 800 mA limit, is it? Or is there anything else I'm unaware of?

Thanks guys.
Vizier87

 

[crutschow]

Absolute Maximum Rating show limits beyond which the device may fail. Since it's a current operated device the voltage is dependent on the current and thus the voltage is not listed in that table as an independent variable.

On page 2 the forward voltage is listed as ranging from 1.9V to 2.5V. It's not totally clear but it's likely this voltage range is seen at the Operating Drive Current listed for the particular device model you have.

 

[Vizier87]

Thanks bro... I'll try using a normal regulator and see where it gets me first..

 

[Vizier87]

okay... bearing the max ratings in mind, I plan to drive the laser using a normal adjustable regulator and a Power BJT, possibly using PWM. Any warnings? I'm all ears.

Also, the monitor diode gives output in what terms? And the ratings of the Peltier cooler aren't given either....

 

[crutschow]

A laser diode is a current operated device similar to an LED. As such it requires current limiting to avoid zapping the diode.

The most efficient way is to use a switching current regulator. (Voltage PWM would require a resistor in series).

If efficiency is not a concern then you can place a resistor in series with the voltage or use a voltage regulator configured as a constant current source.

You can use a LM317 to make a current source by adding a resistor between the output and the load and the adjustment pin also connected to the load. The current approximately equals 1.2/R.

 

[crutschow]

.................
Also, the monitor diode gives output in what terms? And the ratings of the Peltier cooler aren't given either....

The data sheet states the monitor detector responsivity is given in µA/mW. You can use a current-to-voltage converter (such as an op amp configured as a transimpedance amp) to monitor the laser output level.

The data sheet shows the Peltier operating at a current level of 1.3A at 2.5V (last two items on 2nd page).

There is also a thermistor output which can be used to monitor the module temperature.

 

[ronv]

Unless you are going to run it at low power you will need feedback from the monitor to keep it from going into thermal runaway.

 

[Vizier87]

okay guys... thanks for the input!!