MIC29312 based linear driver

[Jufran88]

Isn't Vout regarding the back pin where the extra voltage is dissipated into heat? If so, that can be ignored right?

I tried testing the Enable pin with a different voltage input at 1.5V and 2.4V (I had a CR123 cell that needs to be recharged) and that didn't work either.

 

[rhd]

Vout is where all the current flows from, towards the ADJ pin, where the drop gets measured to make sure it is 1.25V. That's my understanding.

 

[Jufran88]

Gah, I tried different configurations tying ADJ to GND and OUT to GND, but no luck. I guess I'll be waiting for your tests results. I hope you get your package soon! I'm really wondering if I fried it or not. If we both can't get it to work there has to be a design error.

 

[foulmist]

your driver should be working as intended ... I have the same problem with my test load... it seems that the test/dummy load is the problem...

my L1117 driver is set to 431mA but when I connect it to the dummy load I measure 0.01mV or 0.00 mV across the resistor ...... but when I connect my Laser Diode it is working just fineee :wtf:

so I guess this is some problem of the dummy load ... I can't figure out my problem either... but it's not the Driver for sure ... maybe I am missing something .....some help would be highly appreciated ! :beer:

 

[Jufran88]

That does sound strange, but I've used my test load many times to check the current so I'm positive it can't be my test load. I'm gonna try and use a new MIC29312 later today. I'll post my findings.

EDIT:
So, I built another driver and the same thing happened. Outputs only 9mA. Sad face.

 

[foulmist]

That does sound strange, but I've used my test load many times to check the current so I'm positive it can't be my test load. I'm gonna try and use a new MIC29312 later today. I'll post my findings.

EDIT:
So, I built another driver and the same thing happened. Outputs only 9mA. Sad face.

hey man, did you figure it out yet?? :drool:

 

[Jufran88]

No, I didn't but I think I found an error in the board. I'll test it out later when I get off from work.

 

[rhd]

I just wired one up as you had on your board, same issue you were facing.

 

[rhd]

I've been having slightly more success this afternoon with this:
Digi-Key - AP1184T5L-UDI-ND (Manufacturer - AP1184T5L-U)

However, I'm not sure I've got it wired correctly. Confused with the different between Adj Sense FB etc

 

[Jufran88]

So, I tested my guess at what's wrong on the board and it failed again. I'm losing hope on this driver. I had better luck with my LMS1587. Arghh.

Hey rhd, did the boards I sent you arrive yet? Or did you wire up the IC without the PCB? The IC in that link has an awesome dropout! However, it has those control and Vsense pins that can make it confusing and add additonal capacitors.

 

[rhd]

I wired them directly.

It's quite possible that the way this IC works doesn't provide for the fluke that allows 317/1085/1117s to do constant current.

 

[Jufran88]

I'm pretty sure you can use them as a current source. I was reading a write up by Micrel on designing with their LDOs.

Found here: http://www.micrel.com/_PDF/other/LDOBk.pdf

There's a section in there regarding current source design, but it still doesn't explain what could be going wrong.

 

[rhd]

Awwwwww.... We're writing them wrong

IC and load ground are not common. It looks like the resistor goes between ground and adjust, and load between adjust and v out.

Check out page 36

 

[Jufran88]

I was just reading that and I didn't even see it.

I will be be away so I won't be able to test it out until monday. I need to update my boards and I'll send you 1 set for free.

So, if the load ground and the power supply ground aren't common would that pose a problem?

 

[rhd]

Ditto - don't worry, I missed it too

Non common (-) are fine for 405 and 445, just not red and ir. So, for us, no problem.

And truthfully, you can make it work with reds too. Just need to wrap the aixiz in kapton tape once, and wind a copper wire inside the host wall to grab the negative feed.

 

[Jufran88]

Did you already test it out to see if it works that way? And what happened to Jib's post he deleted it.

I'm excited for this driver once again :beer: