I need an analog supply for testing my energy harvesting project as my switch mode bench supply can be a bit too noisy. This is what got me thinking about building an analog supply.
I have used a resistor divider up to this point, but needed something that can source a bit more current.
This is a quick and dirty proof of concept hack of a MIC29152 (1.5A Adjustable) to show that it is possible for its output to go below the 1.24V reference with the help of feedback magic.
It is wired as an inverting amplifying of gain -1 and reference point at 1.24V (instead of usual 0V) The 10 ohms provides a minimum load (>5mA) for the LDO and needs to be reduced for output below 50mV.
This is just a quick hack. The voltage adjustments are bit finicky. Without properly closing the feedback loop to a more stable reference, it isn't all that great. It is already an improvement over a resistor divider.
I have notice that the LDO needs at least 1.6V to operate correctly. Reading between the lines of the following dropout characteristics points to a similar value. Officially they don't list the minimum operating voltage spec as they expect its output to be >=1.24V, so by the time you add in the minimum dropout for the load, you would have meet the requirement.
This has been accounted for in the control voltage design. I might need to increase the voltage slightly.
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