I want to power this 7W 450nm Laser Diode (Nichia NUBM44) using a 3.7V 3.3Ah Li-ion Battery (ICR18650-3350-F). The power required by the laser diode is 5V@4A. Most laser drivers I could find qualified for this type of diode (For example, the ACS4500BU) required a power supply of 6V.
I could use a boost converter in addition to this driver, however I am in a space-constrained project and feel it would be much more convenient if the boost converter could also act as a driver by giving back a constant current.
I managed to find a boost converter (MAX1709) which could take an input anywhere from 0.7-5V and output either 3.3V/5.5V @ 4A. This seems perfect, as my diode takes 5V@4A, and from what I can tell the datasheets claim it has voltage as well as current regulation.
I've been drawing the connections in KiCad, and am somewhat confused with the MAX1709 datasheet on how and what I am supposed to do with certain pins.
This is where I need help:
I want to know if the connections I have so far are correct, and if not what I would need to do to fix them. I also would like to know that even if I got the connections down perfectly, would this be a relatively safe system for powering a laser diode, or is there something more to a laser driver than just a voltage/current regulator?
With that said, here is my current setup in using the MAX1709 to convert a 3.7V, 3.3Ah battery to a 5V@4A power supply. Fair note, there is more to my setup than just the MAX1709, however I will only mention the connections that concern the MAX1709, as I am most unsure if that is correct (I'll leave a description of each of my connections below.)
PGND: Connect all other PGND pins together, then to GND
LX: Connect 2, 3, and 4 LX pins together, as well as Vin, and finally a set of two parallel 150uF capacitors for current stability and a 5A Schottky diode connected to OUT (the datasheet mentioned using an inductor for 'switching frequency', not sure if this matters however.)
FB: PGND (to internally allow for the setting of voltage.)
GND: Connect all other GND pins together, then to GND.
ONA, ONB: Not Connected (Don't need functionality.)
CLK: Not Connected (Or do I need an oscillation for my diode?)
3.3/5: OUT (pull to high to indicate 5V output.)
SS/LIM: Not Connected (Is this safe?)
REF: Not Connected (Not really sure what it's used for.)
EP: Not Connected (In the future I'll probably connect it to the ground plane or add a heatsink to dissipate the heat.)
OUT: Connected to 3.3/5 pin, a 2ohm resistor for 'stability', and a diode to LX pin, and the anode of the laser diode.
Laser diode: Connect anode to OUT pin, and cathode to GND.
Li-ion battery: Connect GND to GND plane, and +3.7V to a pushbutton to turn the laser on/off, then inductor (?), and finally the LX pins
As I mentioned, this was only a list of the connections concerning the MAX1709, but if you see anything else wrong with my setup feel free to point it out.