Datasheet LT3479 (Analog Devices) - 8
| Hersteller | Analog Devices |
| Beschreibung | 3A, Full Featured DC/DC Converter with Soft-Start and Inrush Current Protection |
| Seiten / Seite | 20 / 8 — APPLICATIONS INFORMATION. Capacitor Selection. Table 1. Ceramic Capacitor … |
| Dateiformat / Größe | PDF / 256 Kb |
| Dokumentensprache | Englisch |
APPLICATIONS INFORMATION. Capacitor Selection. Table 1. Ceramic Capacitor Manufacturers. MANUFACTURER. PHONE. WEB
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LT3479
APPLICATIONS INFORMATION Capacitor Selection
can pass a current larger than its rated value without damaging it. Aggressive designs where board space is Low ESR (equivalent series resistance) ceramic capaci- precious will exceed the maximum current rating of the tors should be used at the output to minimize the output inductor to save board space. Consult each manufacturer ripple voltage. Use only X5R or X7R dielectrics, as these to determine how the maximum inductor current is materials retain their capacitance over wider voltage and measured and how much more current the inductor can temperature ranges better than other dielectrics. A 4.7μF reliably conduct. to 10μF output capacitor is suffi cient for most high output current designs. Converters with lower output currents Physically larger inductors provide better effi ciency than may need only a 1μF or 2.2μF output capacitor. smaller ones. Figure 1 shows a 3% to 4% effi ciency gain in using a larger inductor in a 1MHz, 5V to 12V application.
Table 1. Ceramic Capacitor Manufacturers
The effi ciency of the TOKO FDV0630-4R7M, which mea-
MANUFACTURER PHONE WEB
sures 7mm × 7.7mm and 3 mm thick, peaks at 87%. The Taiyo Yuden (408) 573-4150 www.t-yuden.com smaller Sumida CDRH4D28-4R7 which is 5mm × 5mm and AVX (803) 448-9411 www.avxcorp.com 3mm thick yields a peak effi ciency of 85% in an identical Murata (714) 852-2001 www.murata.com application. Thus, if board space is abundant, then larger inductors should be used to maximize effi ciency.
Inductor Selection
90 Several inductors that work well with the LT3479 are listed in Table 2. However, there are many other manufacturers 85 and devices that can be used. Consult each manufacturer 80 TOKO FDV0630-4R7 for more detailed information and their entire range of 75 SUMIDA CDRH4D28-4R7 parts. Ferrite core inductors should be used to obtain the 70 best effi ciency. Choose an inductor that can handle the 65 necessary peak current without saturating, and ensure EFFICIENCY (%) 60 that the inductor has a low DCR (copper-wire resistance) to minimize I2R power losses. A 4.7μH or 10μH inductor 55 will suffi ce for most LT3479 applications. 50 0 0.2 0.4 0.6 0.8 Inductor manufacturers specify the maximum current IOUT (A) 3479 F01 rating as the current where the inductance falls to some percentage of its nominal value—typically 65%. An inductor
Figure 1. Effi ciency vs Inductor Size Table 2. Suggested Inductors MANUFACTURER IDC INDUCTANCE MAX DCR L
×
W
×
H PART NUMBER (A) (μH) (mΩ) (mm) MANUFACTURER
CDRH6D283R0 3 3 24 6.7 × 6.7 × 3.0 Sumida CDRH6D28100 1.7 10 65 6.7 × 6.7 × 3.0 www.sumida.com CDRH4D284R7 1.32 4.7 72 5.0 × 5.0 × 3.0 LM N 05D B4R7M 2.2 4.7 49 5.9 × 6.1 × 2.8 Taiyo Yuden LM N 05D B100K 1.6 10 10 5.9 × 6.1 × 2.8 www.t-yuden.com LQH55DN4R7M01L 2.7 4.7 57 5.7 × 5.0 × 4.7 Murata LQH55DN100M01K 1.7 10 130 5.7 × 5.0 × 4.7 www.murata.com FDV0630-4R7M 4.2 4.7 49 7.0 × 7.7 × 3.0 Toko www.toko.com 3479fc 8
APPLICATIONS INFORMATION Capacitor Selection
can pass a current larger than its rated value without damaging it. Aggressive designs where board space is Low ESR (equivalent series resistance) ceramic capaci- precious will exceed the maximum current rating of the tors should be used at the output to minimize the output inductor to save board space. Consult each manufacturer ripple voltage. Use only X5R or X7R dielectrics, as these to determine how the maximum inductor current is materials retain their capacitance over wider voltage and measured and how much more current the inductor can temperature ranges better than other dielectrics. A 4.7μF reliably conduct. to 10μF output capacitor is suffi cient for most high output current designs. Converters with lower output currents Physically larger inductors provide better effi ciency than may need only a 1μF or 2.2μF output capacitor. smaller ones. Figure 1 shows a 3% to 4% effi ciency gain in using a larger inductor in a 1MHz, 5V to 12V application.
Table 1. Ceramic Capacitor Manufacturers
The effi ciency of the TOKO FDV0630-4R7M, which mea-
MANUFACTURER PHONE WEB
sures 7mm × 7.7mm and 3 mm thick, peaks at 87%. The Taiyo Yuden (408) 573-4150 www.t-yuden.com smaller Sumida CDRH4D28-4R7 which is 5mm × 5mm and AVX (803) 448-9411 www.avxcorp.com 3mm thick yields a peak effi ciency of 85% in an identical Murata (714) 852-2001 www.murata.com application. Thus, if board space is abundant, then larger inductors should be used to maximize effi ciency.
Inductor Selection
90 Several inductors that work well with the LT3479 are listed in Table 2. However, there are many other manufacturers 85 and devices that can be used. Consult each manufacturer 80 TOKO FDV0630-4R7 for more detailed information and their entire range of 75 SUMIDA CDRH4D28-4R7 parts. Ferrite core inductors should be used to obtain the 70 best effi ciency. Choose an inductor that can handle the 65 necessary peak current without saturating, and ensure EFFICIENCY (%) 60 that the inductor has a low DCR (copper-wire resistance) to minimize I2R power losses. A 4.7μH or 10μH inductor 55 will suffi ce for most LT3479 applications. 50 0 0.2 0.4 0.6 0.8 Inductor manufacturers specify the maximum current IOUT (A) 3479 F01 rating as the current where the inductance falls to some percentage of its nominal value—typically 65%. An inductor
Figure 1. Effi ciency vs Inductor Size Table 2. Suggested Inductors MANUFACTURER IDC INDUCTANCE MAX DCR L
×
W
×
H PART NUMBER (A) (μH) (mΩ) (mm) MANUFACTURER
CDRH6D283R0 3 3 24 6.7 × 6.7 × 3.0 Sumida CDRH6D28100 1.7 10 65 6.7 × 6.7 × 3.0 www.sumida.com CDRH4D284R7 1.32 4.7 72 5.0 × 5.0 × 3.0 LM N 05D B4R7M 2.2 4.7 49 5.9 × 6.1 × 2.8 Taiyo Yuden LM N 05D B100K 1.6 10 10 5.9 × 6.1 × 2.8 www.t-yuden.com LQH55DN4R7M01L 2.7 4.7 57 5.7 × 5.0 × 4.7 Murata LQH55DN100M01K 1.7 10 130 5.7 × 5.0 × 4.7 www.murata.com FDV0630-4R7M 4.2 4.7 49 7.0 × 7.7 × 3.0 Toko www.toko.com 3479fc 8