Step 1: Define Requirements

First, specify functional and performance targets:

• Input: 5 V @ 2 A (USB-C)
• Output: 9 V @ 300 mA (3-series LEDs, ~12 W)
• Dimming: Touch-controlled PWM, stepless
• Certification: CE & FCC EMC compliance

Compare three solution paths in the table below and choose the best fit:

Step 2: Topology Analysis

BOOST topology works by storing energy in an inductor and releasing it to step 5 V up to 9 V, maintaining stable output.

Key Features

• Constant-voltage output: perfect for LED constant-current drive
• High efficiency: up to 92%+
• Simple layout: fewer parts, easier debugging

Recommended Components

• MP3429 BOOST IC: 0.5 A–3 A output, integrated synchronous rectification.
• AO3400 MOSFET: 8 mΩ R_DS(on), high-speed switching.
• CDRH3D28-4R7 Inductor: 4.7 µH ±20%, 3 A saturation current.
• 10 µF 0603 ceramic capacitors (Cin/Cout): low ESR, improved transient response.
• 0.18 Ω ±1% sense resistor: ensures accurate current sensing.

Selection tips:

• Match inductor DCR and saturation current to peak load;
• MOSFET voltage rating ≥ 2× max output voltage;
• Consider capacitor voltage rating and temperature coefficient;
• Make sense resistor power rating ≥ 2× dissipation.

Step 3: Calculations & Error Analysis

Inductor Value

Formula: L = (VIN × (1–VIN/VOUT)) / (ΔI × fSW).

Example: 5 V → 9 V, ΔI = 0.3 A, fSW = 1.2 MHz, L ≈ 6.17 µH → choose 6.8 µH.

Sense Resistor

Rs = Vshunt / ILED. With Vshunt = 50 mV, ILED = 300 mA → Rs ≈ 0.167 Ω → choose 0.18 Ω.

Error Analysis

• Inductor tolerance ±20% affects ripple;
• Capacitor ESR impacts output ripple;
• Sense resistor temperature drift affects accuracy.

Step 4: LTspice Simulation Tips

Follow these steps for quick and effective LTspice simulations:

Getting Started

1. Download LTspice XVII from Analog Devices.
2. Import the MP3429 model file (.model) into LTspice and start a new schematic.
3. Add inductor, MOSFET, diode, capacitors—wire up the BOOST topology.
4. Use the directive “.tran 0 5ms” for a 5 ms transient run; click “Run”.
5. After simulation, use the probe tool to measure waveforms; adjust parameters as needed.
6. Perform parameter sweeps with “.step param L 10uH 100uH 10uH” to analyze voltage stability and ripple, then choose optimal values.

These steps will help you efficiently simulate and optimize your BOOST converter.

Step 5: Schematic Design Tips

Follow these guidelines to avoid mistakes and improve quality:

• Align schematic symbols with PCB footprints;
• Use clear net names: VIN, VOUT, ILED;
• Add protection components: TVS diodes, RC snubbers;
• Place test points (TP1, TP2, TP3) in accessible locations;

Step 6: Advanced PCB Layout

Good layout reduces EMI and improves thermal performance:

• Short, wide copper traces for power loops;
• Place Cin close to IC, Cout near LED string;
• Separate high-current ground from signal ground;
• Use multiple vias for heat dissipation and ground returns;

Source: https://commons.wikimedia.org/wiki/File:PCB_screenshot_wiki.png

Step 7: Prototype Assembly & Soldering

1. Order 2-layer, 1.6 mm boards from JLCPCB;
2. Solder small parts before large, using a 360 ℃ iron and 0.6 mm solder;
3. Aim for smooth, shiny joints; use flux for better wetting;

Step 8: Debugging Methods

Once your prototype is built, systematic debugging ensures correct operation:

Short-Circuit Check with Multimeter

• Power off and disconnect;
• Set multimeter to Ohms;
• Measure between VIN and GND—low resistance indicates a short;

Output Voltage Verification

• Apply the specified input voltage;
• Leave output unloaded;
• Measure output: expect 9 V ±0.2 V;

Load Testing with LED

• Connect the LED load at 300 mA;
• Measure current with multimeter in series;
• Ensure stable current around 300 mA;

Step 9: EMC Filtering & Certification

• Input C–L–C: 47 µF + 4.7 µH + 0.1 µF;
• Output EMI filter: 1 µH + 4.7 µF;
• Ground the metal shield;
• Submit for CE/FCC testing per EN55032.

Step 10: Production Optimization & BOM Cost Analysis

Compare key components to balance cost and performance:

Use a Python script with PyVISA to batch-test voltages and currents for higher production efficiency.

Appendix: Tools & Resources

• LTspice Official Download
• PCB Design Deep Dive
• MP3429-Z Datasheet
• Custom PCB Services