LT3071 Current Monitoring

Hi Michael,

Can you double check your design using LTspice?

I suggest trying to copy the layout of the demo board as close as possible.

Hi Ron,

i did a simulation in LTspice. In the simulation everything works fine.

Is there a limitations to the load of the current-monitor? I reduced the value to 1k, but there was no change in the behavior. 

The (measured) behavior of current-output of the monitor is also not linear:

Iload = 1A -> Imon = 445uA

Iload = 1.5A -> Imon = 604uA

Iload = 2A -> Imon = 770uA

Hi MichaelK,

did you see the diagram on bottom left of page 6 of data sheet?
The Imon has a big uncertainty: 1A output current produces 0(!) to 0,7mA Imon.
Also the pink band is braod with all output currents.
So you can not expect Imon to have good linearity or precision.
Additionally the graph has a lower 1A limit. Below you don't know what you'll get!
Also the maximum tolerable voltage at Imon is missing in data sheet.
It looks like Imon has a bias current of 365uA @ Iout = 0A.
Unfortunately in the text it reads differently: "The I MON pin
sources a current typically equal to IOUT/2500 or 400μA
per amp of output current".
So I always reccomend checking the data sheets as thoroughly as Sherlok Holmes would do it.
Another possibility would be, that you've degraded your Imon pin somehow. But this is less probable.

Hi Alexxx,

you're right. I didn't  saw the diagram on page six......!!!!

I think, my Imon pin is working and is not degraded. I know, the monitor is specified only for currents >1A. So i will do some calibration measurements for each regulator and correct the values in software.

Thanks!