[SOLVED] Pulsed laser diode driver

[chippevijaya]

Dear friends,
I want to drive my pulsed laser diode(SPLPL-90) with 12A current, for that i have taken the mic4452(micrel) 12A mosfet driver.
What my question whether i can connect laser diode directly to output of the mic4452 or first i have to connect mosfet to mosfet driver and then laser diode to it.

 

[keith1200rs]

I would suggest you look at the application notes for the Osram lasers

Also, the application note for the hybrid laser is useful:



Keith

 

[dick_freebird]

A bang-bang FET driver is not what you really want. To
get good stability and response the laser diode needs
to be kept lasing (just above lasing threshold) in the "zero"
state, and pulsed to the "1" state at even higher current.
Some sort of wired-or circuit, open drain current mode
is the ticket. If the FET driver has split high side and low
side legs then this could be just resistors, if that is not
too much of a speed impact.

With the bang-bang driver a limiting resistor to set the
max current is a good idea.

 

[keith1200rs]

A bang-bang FET driver is not what you really want. To
get good stability and response the laser diode needs
to be kept lasing (just above lasing threshold) in the "zero"
state, and pulsed to the "1" state at even higher current.

While I agree that is a good way to drive low power lasers, where the threshold current might be 50mA and an extra 5mA takes you to full power, it is not appropriate for high power pulsed lasers. The SPL PL90_3 has a threshold current of 0.75A and pulsed current of 30A. If you put the threshold current through it all the time (typically 4V drop) it would blow up - 3W continuous power in the laser. At 160K/W it would surely die. There would also be eye safety issues if the laser was visible which is a typical use in a laser rangefinder for example.

Keith