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PTH08T250W: Use TRACK pin to drive a laser diode at constant current

Danilo A.
Mastermind 28750 points
Part Number: PTH08T250W

Hi Team,

A customer wants to use the TRACK pin of PTH08T250W to drive a laser diode with nominal voltage of 1.8V at constant current of 12A. He plans to connect a current sense resistor at the output and connect a current sense amplifier or microcontroller to send a proportional voltage to the TRACK pin. Will this circuit work? 

Regards,

Danilo

  • 0
    TI__Genius 17905 points

    Hi Danilo,

    My concern with what you have drawn is that it is adding an additional feedback loop on top of the main voltage regulation loop, and what impact that could have on stability.

    I have asked a colleague more familiar with this part to take a look and advise as well.

    Regards,
    Kris

  • 0
    TI__Mastermind 28020 points

    Hi Danilo,

    I would look at regulating the Vadj voltage instead of the Track voltage. 

    The app-note below shows several simple methods for accomplishing this. The device described in the paper is an older device, but the concept still applies. The PTH08T250W regulates to internal reference voltage of 0.7V instead of 1.25V as shown in the paper.

    Please review and let us know if this will work for you.

    Thanks, Jason

  • 0 in reply to J Arrigo
    TI__Mastermind 28750 points

    Hi Jason and Kris,

    Thank you for your feedback and for sharing the SLTA006A application notes. This resolved the challenge of driving high constant current to the laser.

    Thank you for your support.

    Regards,

    Danilo