Archive:BreadboardPower

           

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
Download	File:Breadboardpower-0.1.zip

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Goal

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.

Implementation

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.

Status

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

Layout

Releases

Version 0.1

File:Breadboardpower-0.1.zip

Bugs:

• 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