From The Munich Maker Lab's Wiki
Jump to navigation Jump to search
Breadboard Power

Release status: beta [box doku]

Description Simple regulated power supply that can be used on breadboards
Author(s)  Simon (SimonRichter)
Last Version  0.1 (2014-11-30)
Platform  electronics
License  PD
Attention.png You are visiting an old member project. The information found on "BreadboardPower" might be out of date.


I'd like to have a simple regulated power supply that can be used on breadboards, providing 5V, 3.3V and a third, adjustable voltage.


The board uses an Allegro A4490 triple regulator and a few supporting components.

For each output, the IC realises a switching FET that is activated when a feedback voltage is below 0.8V, connecting the supply input with the output.

The switched voltage is run through an inductor, and further smoothed with a parallel capacitor. An additional capacitor on the input side further stabilizes the system.

When the FET opens, the inductor builds up a reverse voltage, which is caught in a flyback diode.

The design attempts to minimize the area covered by the traces running non-continuous signals, in order to reduce EM emissions.

Bill of Materials

Id Size Type Value Description
C1 0402 47nF Power-On Reset Time Constant
C2 0402 47nF Charge Pump Capacitor 1
C3 0402 47nF Charge Pump Capacitor 2
C4 0804 47µF Output Filter (1)
C5 0804 47µF Input Filter (1)
C6 0804 47µF Output Filter (2)
C7 0804 47µF Input Filter (2)
C8 0804 47µF Output Filter (3)
C9 0804 47µF Input Filter (3)
D1 LSM115J Flyback Diode (1)
D2 LSM115J Flyback Diode (2)
D3 LSM115J Flyback Diode (3)
D4 0603 LED Power LED
L1 Taiyo Yuden NRG4026T470M 47µH Inductor (1)
L2 Taiyo Yuden NRG4026T470M 47µH Inductor (2)
L3 Taiyo Yuden NRG4026T470M 47µH Inductor (3)
P1 0,1" Connector Bottom Connector, 10x1
P2 0,1" Connector Enable Jumpers, 3x2
R1 0402 10kΩ Pull-Up for Power On Reset
R2 0402 100kΩ Current Limiter Enable (1)
R3 0402 100kΩ Current Limiter Enable (2)
R4 0402 100kΩ Current Limiter Enable (3)
R5 0402 221kΩ Voltage Divider Upper Half (1)
R6 0402 42.1kΩ Voltage Divider Lower Half (1)
R7 0402 215kΩ Voltage Divider Upper Half (2)
R8 0402 68.8kΩ Voltage Divider Lower Half (2)
R9 0402 240Ω Voltage Divider Lower Half (3)
R10 0402 100Ω Current Limiter Power LED
RV1 Bourns PRS11S 50kΩ Voltage Divider Upper Half (3)
U1 Allegro A4490 Regulator IC

You can fudge the resistor values to reach different voltages and change the range covered by the potentiometer.


First PCBs have been manufactured, and one has been assembled. It appears to work. Next: testing.

Work in Progress


Completed Board


Fingers for Scale


Obligatory Glamour Shot





Version 0.1


  • The input and output capacitors use a 0603 footprint rather than 0804. 47µF capacitors are not yet available in that size. Still solderable.
  • The footprint for the LED is too small. Still solderable.
  • The drill size for the potentiometer's mechanical attachment is too small, it should probably be 1.5mm.
  • The resistor values given have only a limited range on the variable output; use a smaller fixed resistor for greater voltages
  • The two rightmost connections are not labeled
  • The current limiting resistors for the enable signals could be placed in line with the enable inputs, so the external circuitry doesn't need a current limiter.
  • The traces could be laid out better