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Building Tiny DDL Driver

I'll leave jib to help you. He understand better than me :p
I was with my email open so I answered fast. I'm going to sleep soon. ;)

good luck with the driver dude, build me one :p
 





Jib... you're really going to hate me soon - I think you should be charging me tuition ;)

Do you know of an IC that fits the following specs:

- LDO (like an LM1117)
- 1.5A or higher current
- Normal LM317 pinout
- Is Negative regulating?

It occurred to me that my upcoming C-Mount build will require a case (+) design. On the bright side, that diode is only ~2.2V, so I can get away with a singe li-ion build, as long as I have an LDO regulator :) Was going to go LM337, but they have an LM317's voltage drop (I believe)
 
From my understanding you don't want to use a neg-reg if your source voltage is positive. Is the case pin not isolated from LD+? The only thing I can think of is using one of those 3A transistors as a Current Sink driver, but I don't know too much about those.
 
With my C-Mount diode, there actually isn't a case pin, the case itself is the LD+. There would be no way whatsoever to isolate it from the case.

My case must be positive.

So neg-regs don't just regulate the (-) rail instead of the (+) ?
 
rhd said:
With my C-Mount diode, there actually isn't a case pin, the case itself is the LD+. There would be no way whatsoever to isolate it from the case.

My case must be positive.

So neg-regs don't just regulate the (-) rail instead of the (+) ?
Click to expand...

Nope, they actually output negative voltages with -1.25V the closest you can get to GND without biasing the Adj pin w/ +1.25V.

Check out the datasheet for the LM337 from OnSemi: http://www.onsemi.com/pub/Collateral/LM337-D.PDF
 
So, regulating the (-) line from the battery at -5V relative to ground, if ground was the case (+) feed from the battery.

^

That's not the same thing as regulating the (+) from the battery to +5V relative to ground, if ground is the (-) feed from the battery?

If not - don't worry about an explanation - I'll take your word for it and go do my own research. I'll need to come up with a new approach though, because I have no choice but to do a case-positive build.
 
rhd said:
So, regulating the (-) line from the battery at -5V relative to ground, if ground was the case (+) feed from the battery.

^

That's not the same thing as regulating the (+) from the battery to +5V relative to ground, if ground is the (-) feed from the battery?

If not - don't worry about an explanation - I'll take your word for it and go do my own research. I'll need to come up with a new approach though, because I have no choice but to do a case-positive build.
Click to expand...

I think you may be right, as this system is not connected to earth ground. Its more about electron flow than potential in relation to earth ground.
 
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