Low-Cost Boost Converter 3.3V Input – 5V Output at 250mA

Rajkumar Sharma
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SKU: EL135097
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This is a low-cost boost converter that converts a 3.3V input to 5V at 250mA load current. The LM2578A chip is used to build this project. The LM2578A is a switching regulator which can easily be set up for such DC-to-DC voltage conversion circuits as the buck, boost and inverting configurations. In this board, the IC is configured as a boost converter. The operating frequency is 50Khz.

Features

Input Voltage 3.3V
Output Voltage 5V DC (+/-5%)
Output Current 250mA
Efficiency Approx 80%
Current Limit 2A
Operating Frequency 50Khz
Thermal Shutdown
PCB Dimensions 38.58 x 17.94mm

Connections

CN1: Pin 1 = 3.3V DC Input, Pin 2 = GND
CN2: Pin 1 = 5V DC Output, Pin 2 = GND

The boost or step-up converter converts a DC voltage to a higher DC voltage. When the switch software is turned on, energy is stored in the inductor L and the inductor current iL ramps up at a slope determined by the input voltage. Diode D is off during this period. Once the switch, SW, turns off, diode D starts to conduct and the energy stored in the inductor is released to the load. Current in the inductor ramps down at a slope determined by the difference between the input and output voltages.

The LM2578A is a switching regulator which can easily be set up for such DC-to-DC voltage conversion circuits as the buck, boost and inverting configurations. The LM2578A features a unique comparator input stage which not only has separate pins for both the inverting and non-inverting inputs but also provides an internal 1.0V reference to each input, thereby simplifying circuit design and p.c. board layout. The output can switch up to 750 mA and has output pins for its collector and emitter to promote design flexibility. An external current limit terminal may be referenced to either the ground or the Vin terminal, depending upon the application. In addition, the LM2578A has an onboard oscillator, which sets the switching frequency with a single external capacitor from <1 Hz to 100 kHz (typical).

Schematic

Parts List

NO	QNTY	REF.	DESC	MANUFACTURER	SUPPLIER	SUPPLIER PART NO
1	2	CN1,CN2	2 PIN MALE HEADER PITCH 2.54MM	WURTH	DIGIKEY	732-5315-ND
2	1	C1	220uF/16V ELECTROLYTIC 6.3MM	ELITE	DIGIKEY	4191-EV1C221MP26311EUCT-ND
3	1	C2	470uF/16V ELECTROLYTIC 8MM	NICHICON	DIGIKEY	UVR1C471MPDDTB-ND
4	3	C3,C4,C6	1nF/50V CERAMIC SMD SIZE 0805	MURATA/YAGEO	DIGIKEY
5	1	C5	22PF/50V CERAMIC SMD SIZE 0805	MURATA/YAGEO	DIGIKEY
6	1	D1	SS34 FAST SWITCHING DIODE	ONSEMI	DIGIKEY	SS34FSCT-ND
7	1	L1	33uH/2A	PULSE ELECTRONICS	DIGIKEY	553-AWVS00808040330M00CT-ND
8	1	Q1	MJD44H11T4G DPK	ONSEMI	DIGIKEY	MJD44H11T4GOSCT-ND
9	1	R1	140K 1% SMD SIZE 0805	MURATA/YAGEO	DIGIKEY
10	1	R2	11K 1% SMD SIZE 0805	MURATA/YAGEO	DIGIKEY
11	2	R3,R7	200E 1% SMD SIZE 0805	MURATA/YAGEO	DIGIKEY
12	1	R4	0.05E 1% SMD SIZE 2512	MURATA/YAGEO	DIGIKEY
13	1	R5	1E 1% SMD SIZE 0805	MURATA/YAGEO	DIGIKEY
14	1	R6	43K 1% SMD SIZE 0805	MURATA/YAGEO	DIGIKEY
15	1	U1	LM3578 SOIC8	TI	DIGIKEY	296-35906-1-ND