Article

5 V Power Controller

Battery operation from 2 V to 8 V

These days many components and microcontrollers are designed for low-voltage operation and can be powered directly from a battery. For various reasons, however, it is often necessary to power them from a 5 V supply. Designing a high-efficiency supply is time-consuming, and so here we present a universal solution in the form of our 5 V power controller.

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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

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PCB

Download Gerber file: 090719-1-V20

Extra info / Update

• Input voltage range 2 V to 8 V (for example from two AA cells or two lithium-ion or lithium-polymer cells)
• Power a 5 V circuit drawing up to 150 mA using two AA cells
• Especially designed for 5 V microcontroller circuits
• Efficiency: 75 % at 2 V and >76 % from 3 V to 8 V input voltage
• Standard, readily available components
• All connections on 2.54 mm pitch headers
• Soft-off function under processor control
• Power on button can also be used as general input button
• Low current consumption in soft-off standby

Component list

Resistors
(all SMD 0805, 1%)
R1,R2,R4 = 10kOhm
R3 = 10Ohm (see text)
R5 = 100kOhm
R6 = 560kOhm
R7 = 680kOhm
Capacitors
C1,C6,C7 = 100µF 25V SMD (e.g. Farnell # 1735335)
C2,C8 = 100nF 100V SMD (e.g. Reichelt.de # SMD-1812 100N, see text)
C3 = 1µF 25V SMD tantalum 0805 (e.g. Farnell # 1135280)
C4 = 10nF 100V SMD (e.g. Reichelt.de # SMD-1812 10N, see text)
C5 = 220µF 35V SMD (e.g. Farnell # 9695877)
Inductors
L1,L2 = 33µH, 2A, 0.12Ohm SMD (e.g. Farnell # 1612699, Reichelt.de # L-PISM 33µ)
L3 = 27µH, 0.8A, 0.26Ohm, SMD (e.g. Farnell # 1539570)
Semiconductors
(all SMD)
D1,D2 = BAT54S (SOT-23, STMicroelectronics)
D3 = MBRS340 (SMC, ON Semiconductor)
T1 = BSS138N (SOT-23, Infineon)
IC1 = LT1302 (SO-8, Linear Technology)
Miscellaneous
K1,K2 = 2-pin pinheader
K3 = 5-pin pinheader
PCB # 090719, see Elektor Shop or www.elektor.com/090719
PCB artwork download (free)