Step-Up Boost Converter Circuit Design: Using the MT3608 for 5V to 12V Applications
Step-Up Boost Converter Circuit Design: Using the MT3608 for 5V to 12V Applications
Step-Up Boost Converter Circuit Design: Using the MT3608 for 5V to 12V Applications
📅 Updated: April 2026 | ⏱ 8 min read | 🔋 Boost Converter Design
Many portable electronics, sensors, and IoT devices operate from a single Li‑ion battery (3.7–4.2V) or a USB power source (5V), yet they often require a higher voltage for peripherals such as small fans, LED strips, op‑amps, or relay coils. A boost converter (step‑up DC‑DC converter) efficiently raises the input voltage to a stable, higher output. One of the most popular and affordable boost converter ICs for low‑power applications is the MT3608. This article provides a complete guide to designing a 5V to 12V boost converter using the MT3608, covering circuit schematic, component selection, PCB layout tips, and performance considerations.
What Is the MT3608?
The MT3608 is a monolithic, current‑mode, fixed‑frequency boost converter IC capable of delivering up to 2A of switch current. It operates at a switching frequency of 1.2 MHz, which allows the use of small, low‑profile inductors and ceramic capacitors. The input voltage range is 2V to 24V, making it suitable for single‑cell Li‑ion batteries (3.7V) and USB (5V). The output voltage can be set up to 28V using an external resistor divider. The MT3608 includes built‑in over‑current protection, thermal shutdown, and an internal soft‑start function to limit inrush current. It is available in a tiny SOT‑23‑6 package, ideal for compact designs.
💡 Key features of MT3608:
• Input: 2V to 24V
• Output: up to 28V (adjustable)
• Switch current limit: 2A (typical)
• Switching frequency: 1.2 MHz
• Efficiency: up to 93%
• Internal soft‑start, over‑current protection, thermal shutdown
• Small SOT‑23‑6 package
5V to 12V Boost Converter Circuit Design
The typical application circuit for the MT3608 requires only a handful of external components: an inductor, a Schottky diode, input/output capacitors, and two feedback resistors. The schematic below shows a 5V to 12V boost converter capable of supplying up to ~300–400 mA output current (depending on input voltage and efficiency).
5V input ──┬── C1 ──┬── L1 ──┬── D1 ──┬── C2 ──┬── 12V output
│ │ │ │ │
(+) SW (pin1) │ (+) │
│ │ │ │ │
└────────┴────────┼────────┴────────┘
│
└── R1 ──┬── FB (pin4)
│
R2
│
GND
Simplified schematic – refer to datasheet for complete pinout.
Component Selection
- Inductor (L1): A 10 µH to 22 µH power inductor with saturation current rating > 2.5A is recommended. For a 5V input and 12V output, 22 µH works well. Use a shielded inductor to reduce EMI. Example: CDRH104R‑220 (22 µH, 3.2A).
- Schottky diode (D1): Choose a diode with low forward voltage drop (<0.5V) and fast switching. Current rating should be at least the peak switch current (2A). Common choices: SS34 (3A/40V), 1N5819 (1A/40V) for lower power.
- Input capacitor (C1): 10 µF to 22 µF, low‑ESR ceramic (X5R or X7R). For 5V input, a 10 µF/16V ceramic capacitor is sufficient.
- Output capacitor (C2): 22 µF to 100 µF, low‑ESR ceramic. Use at least 22 µF/25V for 12V output. Adding a 0.1 µF ceramic in parallel reduces high‑frequency noise.
- Feedback resistors (R1, R2): The output voltage is set by: Vout = 0.6V × (1 + R1/R2). For Vout = 12V, choose R2 = 10 kΩ, then R1 = (12/0.6 – 1) × 10k = 190kΩ. Use standard 1% resistors (e.g., 191 kΩ).
- Optional feedforward capacitor (Cff): A 100 pF capacitor in parallel with R1 can improve transient response and stability.
⚠️ Important: The MT3608 has a switch current limit of 2A (typical). This limits the maximum output power. For 5V input and 12V output at 90% efficiency, the maximum output current is approximately (2A × 5V × 0.9) / 12V ≈ 0.75A. In practice, for continuous operation, stay below 400–500 mA to avoid overheating.
Calculating Output Voltage and Component Values
The feedback pin (FB) regulates to 0.6V. Using a voltage divider from the output:
Vout = 0.6 × (1 + R1/R2)
To minimize quiescent current, choose R2 between 10 kΩ and 100 kΩ. R1 is then calculated as:
R1 = R2 × (Vout/0.6 – 1)
For a 12V output with R2 = 10 kΩ, R1 = 190 kΩ (use 191 kΩ, 1%). For a 5V output (from a higher input), R1 = 73.3 kΩ (use 73.2 kΩ).
The inductor ripple current (ΔIL) and peak current (IL,peak) should be checked to ensure the inductor does not saturate. For a boost converter:
ΔIL = (Vin × D) / (fsw × L)
where D = 1 – (Vin/Vout) for ideal boost. At 5V in, 12V out, D ≈ 0.583. fsw = 1.2 MHz, L = 22 µH → ΔIL ≈ 0.11 A. Peak current ≈ Iin,avg + ΔIL/2. With Iout = 0.3A, Iin,avg ≈ (12×0.3)/(5×0.9) = 0.8A, so IL,peak ≈ 0.85A — well within the 2A limit.
📐 Design example summary:
Input: 5V (USB) → Output: 12V @ 300 mA
L1 = 22 µH (saturation ≥ 2A)
D1 = SS34 (3A/40V)
C1 = 10 µF, C2 = 47 µF ceramic
R2 = 10 kΩ, R1 = 191 kΩ (1%)
Efficiency ≈ 88–92%
Peak inductor current ≈ 0.85A (safe)
PCB Layout Guidelines
Proper layout is critical for stability, efficiency, and EMI. Follow these rules when designing your PCB:
- Keep the switching loop small: The loop formed by C1, the MT3608’s SW pin, L1, D1, and C2 must be as tight as possible. Use a ground plane and place components close together.
- Place input capacitor close to the IC: C1 should be as near as possible to the VIN and GND pins of the MT3608 to reduce voltage spikes.
- Use short, wide traces for power paths: Input and output current paths should be wide to reduce resistive losses.
- Keep feedback resistors away from the inductor: The FB pin is high‑impedance; route the feedback trace away from the inductor and SW node to avoid noise coupling.
- Provide a solid ground plane: Use a dedicated ground plane under the converter for low impedance and thermal relief.
- Add thermal vias: The exposed pad of the MT3608 (if present) should be soldered to the PCB with multiple vias to the ground plane for heat dissipation.
Performance and Efficiency
The MT3608 achieves peak efficiency of around 90–93% at moderate loads. For a 5V to 12V conversion, typical efficiency at 100–300 mA is 88–92%. At very light loads (<20 mA), efficiency drops due to fixed quiescent current (≈ 100 µA) and switching losses. At high loads (>500 mA), efficiency may drop due to I²R losses in the inductor and MOSFET. The IC will enter thermal shutdown if the die temperature exceeds 160°C — ensure adequate copper area for cooling.
Measured performance from a well‑built MT3608 module:
- Vin = 5.0V, Vout = 12.0V, Iout = 300 mA → η ≈ 90%
- Output ripple: 30–50 mVpp at 1.2 MHz (depending on output capacitor ESR)
- Line regulation: <0.5% from 4.5V to 5.5V input
- Load regulation: <2% from 50 mA to 400 mA
Applications and Project Ideas
- Power 12V LED strips from a 5V USB power bank.
- Drive small 12V fans for cooling enclosures or 3D printers.
- Provide ±12V rails for op‑amp circuits (using two boost converters or one with a coupled inductor).
- Power relay coils in Arduino or ESP32 projects.
- Create a portable 12V lab supply from a single Li‑ion battery (requires 3.7V to 12V conversion – the MT3608 can boost from 3.7V as well).
- Upgrade a 5V-powered device to use higher voltage sensors or actuators.
Using Pre‑Built MT3608 Modules
If you prefer not to design your own PCB, ready‑made MT3608 boost converter modules are widely available for under $2. They typically include the IC, inductor, diode, capacitors, and a multi‑turn potentiometer for output voltage adjustment. These modules are excellent for rapid prototyping. However, be aware that some cheap modules use counterfeit MT3608 ICs or underrated inductors. When using a pre‑built module, always measure the output voltage before connecting your load and verify that the inductor does not overheat at full load.
⚠️ Caution: The MT3608 does not have output over‑voltage protection or reverse input protection. If the feedback divider opens, the output can rise to dangerous levels (up to Vin + Vdiode). Always include a Zener clamp (e.g., 15V) at the output for safety when experimenting.
Conclusion
The MT3608 boost converter IC offers an inexpensive, compact, and efficient solution for 5V to 12V step‑up applications up to a few hundred milliamps. With a minimal external component count and a fixed 1.2 MHz switching frequency, it is ideal for hobbyist projects, portable devices, and embedded systems. By following the component selection guidelines and PCB layout tips provided in this article, you can design a reliable boost converter that delivers stable 12V power from a USB source or single‑cell Li‑ion battery. Whether you build your own circuit or use a pre‑assembled module, the MT3608 is a versatile workhorse for countless low‑power boost applications. © 2026 Power Electronics Guide – Your resource for MT3608 boost converter design, 5V to 12V step‑up circuits, and DC‑DC conversion tutorials.