LTC3780, preparing the board

 

First, let's remove the 3.3k resistor that ties Feedback to the ground.

That's that one :


Remove the voltage potentiometer. Ive replaced it with a header. The pinout on the below picture is :

FB (RED)

VO (Green)

VO (Green)





Cut the small track between the 2 Vos so that the middle one is connected to nothing.

On the back let's put a small perf board (with the usual craftmanship)  that does the wiring described in the previous post, except the digital pot. i.e.




So now we have on the pin header :
Red : Direct feedback, we'll use that later for current control.
Green(middle)  : Voltage potentiometer (0..110k) referenced to ground.
Green(bottom) : VOut

Power it on with nothing connected : Vo=1.6v = 2xFeedback = as expected since FB=vo/2 (two 100k resistors), the current is very small the diode effect is ~0.


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