Tiny power supply

I see a lot of examples of electronic experiments, mainly with low power devices, powered by batteries. If this could be a handy and smart solution for experiments and/or wireless/remote applications, it might not be  so desirable for all the others. Also could be a pricey one, sometime.

I always use a desk power supply, with enough resources (adjustable from 0 V to 40 V and current 0 A to 10 A), but sometimes I feel better with some other approach with a smaller footprint 😉 – my desk (work table) is so tiny…

My solution is a shortcut between a desk (bench) power supply and an dedicated one. During the last months I had the occasion to play with some nice pieces of electronic named PTN78060WAS, a pretty cryptic name, doesn’t it? That is, according to data sheet, a “high-efficiency, step-down integrated switching regulator”. It is made by Texas Instruments.

The coin is 1 eurocent and is a little smaller than an 1 US cent, in diameter and not in value 😉

Because there are two voltages, generally used with the current low power devices, 3.3V and 5V, I choose to build my tiny power supply with these two values. The standard application is shown on the first page of the data sheet and comprise a required resistor to set the output value of voltage. There is a table, on page 11, with Output Voltage Set-Point Resistor Values, therefore  for 3.3V  Rset = 79.3 kΩ and for 5.0V Rset = 21.0 kΩ. The final schematic is the same with these values:

Ci = 10 microF, ceramic (not polarized)

Co = 100 microF, polarized

Rset = 79.3 kΩ (for 3.3V) and 21.0 kΩ (for 5.0V)

Could be a little hard to find these exact values for Rset but the old trick with serial and parallel connection might give you a hand to figure out some closer values. Or you can use two potentiometers: 100 kΩ and 50 kΩ.

The upper is 3.3V and the lower is 5V

 

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