Datasheet LTC3410B (Analog Devices) - 8
| Hersteller | Analog Devices |
| Beschreibung | 2.25MHz, 300mA Synchronous Step-Down Regulator in SC70 |
| Seiten / Seite | 16 / 8 — APPLICATIO S I FOR ATIO. Inductor Core Selection. Figure 1. High … |
| Dateiformat / Größe | PDF / 297 Kb |
| Dokumentensprache | Englisch |
APPLICATIO S I FOR ATIO. Inductor Core Selection. Figure 1. High Efficiency Step-Down Converter
Modelllinie für dieses Datenblatt
- LTC3410BESC6#PBF LTC3410BESC6#TRMPBF LTC3410BESC6#TRPBF LTC3410BESC6-1.2#PBF LTC3410BESC6-1.2#TRMPBF LTC3410BESC6-1.2#TRPBF LTC3410BESC6-1.5#PBF LTC3410BESC6-1.5#TRMPBF LTC3410BESC6-1.5#TRPBF LTC3410BESC6-1.8#PBF LTC3410BESC6-1.8#TRMPBF LTC3410BESC6-1.8#TRPBF LTC3410BESC6-1.875#PBF LTC3410BESC6-1.875#TRMPBF LTC3410BESC6-1.875#TRPBF
Textversion des Dokuments
LTC3410B
U U W U APPLICATIO S I FOR ATIO
V 4.7µH
Inductor Core Selection
IN V 2.7V V OUT IN SW 1.2V TO 5.5V C 10pF IN C Different core materials and shapes will change the size/ 2.2µF LTC3410B OUT 2.2µF CER RUN current and price/current relationship of an inductor. Tor- CER VFB oid or shielded pot cores in ferrite or permalloy materials 232k GND are small and don’t radiate much energy, but generally cost 464k more than powdered iron core inductors with similar 3410 F01 electrical characteristics. The choice of which style induc- tor to use often depends more on the price vs size require-
Figure 1. High Efficiency Step-Down Converter
ments and any radiated field/EMI requirements than on what the LTC3410B requires to operate. Table 1 shows The basic LTC3410B application circuit is shown in Fig- some typical surface mount inductors that work well in ure 1. External component selection is driven by the load LTC3410B applications. requirement and begins with the selection of L followed by C
Table 1. Representative Surface Mount Inductors
IN and COUT.
MAX DC Inductor Selection MANUFACTURER PART NUMBER VALUE CURRENT DCR HEIGHT
Taiyo Yuden CB2016T2R2M 2.2µH 510mA 0.13Ω 1.6mm For most applications, the value of the inductor will fall in CB2012T2R2M 2.2µH 530mA 0.33Ω 1.25mm the range of 2.2µH to 4.7µH. Its value is chosen based on LBC2016T3R3M 3.3µH 410mA 0.27Ω 1.6mm the desired ripple current. Large value inductors lower Panasonic ELT5KT4R7M 4.7µH 950mA 0.2Ω 1.2mm ripple current and small value inductors result in higher Sumida CDRH2D18/LD 4.7µH 630mA 0.086Ω 2mm ripple currents. Higher VIN or VOUT also increases the ripple Murata LQH32CN4R7M23 4.7µH 450mA 0.2Ω 2mm current as shown in Equation 1. A reasonable starting point Taiyo Yuden NR30102R2M 2.2µH 1100mA 0.1Ω 1mm for setting ripple current is ∆I NR30104R7M 4.7µH 750mA 0.19Ω 1mm L = 120mA (40% of 300mA). FDK FDKMIPF2520D 4.7µH 1100mA 0.11Ω 1mm ∆ 1 V FDKMIPF2520D 3.3µH 1200mA 0.1Ω 1mm I OUT L = ⎛ ⎞ ( VOUT 1 (1) FDKMIPF2520D 2.2µH 1300mA 0.08Ω 1mm f)( ) − L ⎝⎜ VIN ⎠⎟ The DC current rating of the inductor should be at least
CIN and COUT Selection
equal to the maximum load current plus half the ripple In continuous mode, the source current of the top MOS- current to prevent core saturation. Thus, a 360mA rated FET is a square wave of duty cycle V inductor should be enough for most applications (300mA OUT/VIN. To prevent large voltage transients, a low ESR input capacitor sized + 60mA). For better efficiency, choose a low DC-resistance for the maximum RMS current must be used. The maxi- inductor. mum RMS capacitor current is given by: ⎡ 1/2 V ⎣ (V − V )⎤ OUT IN OUT ⎦ C required I I IN RMS ≅ OMAX VIN 3410bfa 8
U U W U APPLICATIO S I FOR ATIO
V 4.7µH
Inductor Core Selection
IN V 2.7V V OUT IN SW 1.2V TO 5.5V C 10pF IN C Different core materials and shapes will change the size/ 2.2µF LTC3410B OUT 2.2µF CER RUN current and price/current relationship of an inductor. Tor- CER VFB oid or shielded pot cores in ferrite or permalloy materials 232k GND are small and don’t radiate much energy, but generally cost 464k more than powdered iron core inductors with similar 3410 F01 electrical characteristics. The choice of which style induc- tor to use often depends more on the price vs size require-
Figure 1. High Efficiency Step-Down Converter
ments and any radiated field/EMI requirements than on what the LTC3410B requires to operate. Table 1 shows The basic LTC3410B application circuit is shown in Fig- some typical surface mount inductors that work well in ure 1. External component selection is driven by the load LTC3410B applications. requirement and begins with the selection of L followed by C
Table 1. Representative Surface Mount Inductors
IN and COUT.
MAX DC Inductor Selection MANUFACTURER PART NUMBER VALUE CURRENT DCR HEIGHT
Taiyo Yuden CB2016T2R2M 2.2µH 510mA 0.13Ω 1.6mm For most applications, the value of the inductor will fall in CB2012T2R2M 2.2µH 530mA 0.33Ω 1.25mm the range of 2.2µH to 4.7µH. Its value is chosen based on LBC2016T3R3M 3.3µH 410mA 0.27Ω 1.6mm the desired ripple current. Large value inductors lower Panasonic ELT5KT4R7M 4.7µH 950mA 0.2Ω 1.2mm ripple current and small value inductors result in higher Sumida CDRH2D18/LD 4.7µH 630mA 0.086Ω 2mm ripple currents. Higher VIN or VOUT also increases the ripple Murata LQH32CN4R7M23 4.7µH 450mA 0.2Ω 2mm current as shown in Equation 1. A reasonable starting point Taiyo Yuden NR30102R2M 2.2µH 1100mA 0.1Ω 1mm for setting ripple current is ∆I NR30104R7M 4.7µH 750mA 0.19Ω 1mm L = 120mA (40% of 300mA). FDK FDKMIPF2520D 4.7µH 1100mA 0.11Ω 1mm ∆ 1 V FDKMIPF2520D 3.3µH 1200mA 0.1Ω 1mm I OUT L = ⎛ ⎞ ( VOUT 1 (1) FDKMIPF2520D 2.2µH 1300mA 0.08Ω 1mm f)( ) − L ⎝⎜ VIN ⎠⎟ The DC current rating of the inductor should be at least
CIN and COUT Selection
equal to the maximum load current plus half the ripple In continuous mode, the source current of the top MOS- current to prevent core saturation. Thus, a 360mA rated FET is a square wave of duty cycle V inductor should be enough for most applications (300mA OUT/VIN. To prevent large voltage transients, a low ESR input capacitor sized + 60mA). For better efficiency, choose a low DC-resistance for the maximum RMS current must be used. The maxi- inductor. mum RMS capacitor current is given by: ⎡ 1/2 V ⎣ (V − V )⎤ OUT IN OUT ⎦ C required I I IN RMS ≅ OMAX VIN 3410bfa 8