Datasheet LTC3670 (Analog Devices) - 10

link to page 10 LTC3670
APPLICATIONS INFORMATION Buck Regulator Inductor Selection
Different core materials and shapes will change the size/cur- Many different sizes and shapes of inductors are avail- rent and price/current relationship of an inductor. Toroid able from numerous manufacturers. Choosing the right or shielded pot cores in ferrite or Permalloy materials inductor from such a large selection of devices can be are small and do not radiate much energy, but generally overwhelming, but following a few basic guidelines will cost more than powdered iron core inductors with similar make the selection process much simpler. electrical characteristics. Inductors that are very thin or have a very small volume typically have much higher core The buck regulator is designed to work with inductors in and DCR losses, and will not give the best efficiency. The the range of 2.2µH to 10µH. A 4.7µH inductor is a good choice of which style inductor to use often depends more starting point. Larger value inductors reduce ripple cur- on the price vs size, performance, and any radiated EMI rent which improves output ripple voltage. Lower value requirements than on what the buck regulator needs to inductors result in higher ripple current and improved operate. transient response time. To maximize efficiency, choose an inductor with a low DC resistance. Choose an inductor Table 1 shows several inductors that work well with the with a DC current rating at least 1.5 times larger than the buck regulator. These inductors offer a good compromise maximum load current to ensure that the inductor does not in current rating, DCR and physical size. Consult each saturate during normal operation. If output short-circuit manufacturer for detailed information on their entire is a possible condition, the inductor should be rated to selection of inductors. handle the maximum peak current specified for the buck regulator.
Table 1. Recommended Inductors for the Buck Regulator L MAXIMUM IDC MAXIMUM DCR SIZE in mm INDUCTOR TYPE (µH) (A) (Ω) (L
×
W
×
H) MANUFACTURER
EPL2014-472ML 4.7 1.3 0.254 1.8 × 2.0 × 1.4 Coilcraft www.coilcraft.com LPS3015 4.7 1.1 0.2 3.0 × 3.0 × 1.5 3.3 1.3 0.13 3.0 × 3.0 × 1.5 DE2818C 4.7 1.25 0.072 3.0 × 2.8 × 1.8 Toko 3.3 1.45 0.053 3.0 × 2.8 × 1.8 www.toko.com DE2812C 4.7 1.15 0.13* 3.0 × 2.8 × 1.2 3.3 1.37 0.105* 3.0 × 2.8 × 1.2 CDRH3D16 4.7 0.9 0.11 4.0 × 4.0 × 1.8 Sumida www.sumida.com CDRH2D11 4.7 0.5 0.17 3.2 × 3.2 × 1.2 3.3 0.6 0.123 3.2 × 3.2 × 1.2 SD3118 4.7 1.3 0.162 3.1 × 3.1 × 1.8 Cooper 3.3 1.59 0.113 3.1 × 3.1 × 1.8 www.cooperet.com *Typical DCR Rev A 10 For more information www.analog.com Document Outline Features Description Applications Typical Application Absolute Maximum Ratings Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Typical Application Related Parts