Selecting the right SMD inductor for a DC-DC converter is one of the most common tasks in power electronics design. The inductor value, saturation current, DCR and package size directly determine efficiency, transient response and solution size.
This guide walks through the key parameters for SMD inductors and how to choose the right part for your buck, boost or buck-boost converter.
Shaanxi SiRui Technology Co., Ltd. manufactures SMD power inductors and custom wound inductors for DC-DC applications. Contact: sales@sirui-tech.com | Web: www.sirui-tech.com
1. Key Parameters
- Inductance (L): determines ripple current; higher L = lower ripple but larger size
- Saturation current (Isat): DC current at which L drops 30%; must exceed peak inductor current
- RMS current (Irms): current at rated temperature rise; must exceed RMS current
- DCR: winding resistance; lower = higher efficiency
- Package size: height critical for portable devices (1.0–3.0 mm typical)
2. Calculating Inductance (Buck)
L = (Vin – Vout) × Vout / (Vin × f_sw × ΔI_L). Typical ripple: 20–40% of rated current.
3. SMD Inductor Types
| Type | Shielded | Height | Best For |
|---|---|---|---|
| Molded SMD | Yes | 1.0–3.0 mm | High density, low EMI |
| Wire-wound drum | No | 2.0–5.0 mm | Low cost, high current |
| Multilayer chip | Yes | 0.8–2.0 mm | Low current (<2A) |
4. Common Mistakes
- Only looking at Isat, not Irms—part may overheat
- Ignoring DCR—at high current, DCR loss dominates efficiency
- Choosing too high inductance—larger size, slower transient
- Forgetting temperature effect on DCR
5. Sirui-Tech SMD Products
- Molded SMD inductors: shielded, 1–100 μH, up to 30 A
- Wire-wound SMD: cost-effective options
- Custom designs: wound to customer specs
Conclusion
SMD inductor selection balances inductance, saturation current, DCR and size. Size for peak current plus margin, and verify both Isat and Irms. For high-efficiency designs, DCR is the key parameter.
Need SMD inductors? Contact Sirui-Tech at sales@sirui-tech.com with your inductance, peak current and target DCR.