Datasheet LT3475, LT3475-1 (Analog Devices) - 10
| Hersteller | Analog Devices |
| Beschreibung | Dual Step-Down 1.5A LED Driver |
| Seiten / Seite | 20 / 10 — APPLICATIONS INFORMATION. Table 2. Inductors. VALUE. IRMS. DCR. HEIGHT. … |
| Dateiformat / Größe | PDF / 249 Kb |
| Dokumentensprache | Englisch |
APPLICATIONS INFORMATION. Table 2. Inductors. VALUE. IRMS. DCR. HEIGHT. PART NUMBER. (A). ( ). (mm). Sumida
Modelllinie für dieses Datenblatt
Textversion des Dokuments
LT3475/LT3475-1
APPLICATIONS INFORMATION
current have signifi cantly increased. Exceeding VIN(MAX)
Table 2. Inductors
is safe if the external components have adequate ratings
VALUE IRMS DCR HEIGHT
to handle the peak conditions and if the peak inductor
PART NUMBER (
μ
H) (A) ( ) (mm)
current does not exceed 3.2A. A saturating inductor may
Sumida
further reduce performance. CR43-3R3 3.3 1.44 0.086 3.5 CR43-4R7 4.7 1.15 0.109 3.5 CDRH4D16-3R3 3.3 1.10 0.063 1.8 VOUT CDRH4D28-3R3 3.3 1.57 0.049 3.0 500mV/DIV (AC COUPLED) CDRH4D28-4R7 4.7 1.32 0.072 3.0 IL 1A/DIV CDRH6D26-5R0 5.0 2.20 0.032 2.8 CDRH6D26-5R6 5.6 2.0 0.036 2.8 CDRH5D28-100 10 1.30 0.048 3.0 VSW 20V/DIV CDRH5D28-150 15 1.10 0.076 3.0 CDRH73-100 10 1.68 0.072 3.4 3475 F04 CDRH73-150 15 1.33 0.130 3.4
Figure 4. Operation above VIN(MAX). Output Ripple and Peak Inductor Current Increases
CDRH104R-150 15 3.1 0.050 4.0
Coilcraft
DO1606T-332 3.3 1.30 0.100 2.0
Inductor Selection and Maximum Output Current
DO1606T-472 4.7 1.10 0.120 2.0 A good fi rst choice for the inductor value is: DO1608C-332 3.3 2.00 0.080 2.9 1.2MHz DO1608C-472 4.7 1.50 0.090 2.9 L = (VOUT + VF )• f MOS6020-332 3.3 1.80 0.046 2.0 MOS6020-472 10 1.50 0.050 2.0 where VF is the voltage drop of the catch diode (~0.4V), DO3316P-103 10 3.9 0.038 5.2 f is the switching frequency and L is in μH. With this value DO3316P-153 15 3.1 0.046 5.2 the maximum load current will be above 1.6A at all duty cycles. The inductor’s RMS current rating must be greater The optimum inductor for a given application may differ than the maximum load current and its saturation current from the one indicated by this simple design guide. A larger should be at least 30% higher. For highest effi ciency, value inductor provides a higher maximum load current, and the series resistance (DCR) should be less than 0.15Ω. reduces the output voltage ripple. If your load is lower than Table 2 lists several vendors and types that are suitable. the maximum load current, then you can relax the value of the For robust operation at full load and high input voltages inductor and operate with higher ripple current. This allows (VIN > 30V), use an inductor with a saturation current you to use a physically smaller inductor, or one with a lower higher than 3.2A. DCR resulting in higher effi ciency. In addition, low inductance may result in discontinuous mode operation, which further reduces maximum load current. For details of maximum output current and discontinuous mode operation, see Linear Technology’s Application Note 44. Finally, for duty cycles greater than 50% (VOUT/VIN > 0.5), a minimum inductance is required to avoid sub-harmonic oscillations: 800kHz LMIN = (VOUT + VF )• f 3475fb 10
APPLICATIONS INFORMATION
current have signifi cantly increased. Exceeding VIN(MAX)
Table 2. Inductors
is safe if the external components have adequate ratings
VALUE IRMS DCR HEIGHT
to handle the peak conditions and if the peak inductor
PART NUMBER (
μ
H) (A) ( ) (mm)
current does not exceed 3.2A. A saturating inductor may
Sumida
further reduce performance. CR43-3R3 3.3 1.44 0.086 3.5 CR43-4R7 4.7 1.15 0.109 3.5 CDRH4D16-3R3 3.3 1.10 0.063 1.8 VOUT CDRH4D28-3R3 3.3 1.57 0.049 3.0 500mV/DIV (AC COUPLED) CDRH4D28-4R7 4.7 1.32 0.072 3.0 IL 1A/DIV CDRH6D26-5R0 5.0 2.20 0.032 2.8 CDRH6D26-5R6 5.6 2.0 0.036 2.8 CDRH5D28-100 10 1.30 0.048 3.0 VSW 20V/DIV CDRH5D28-150 15 1.10 0.076 3.0 CDRH73-100 10 1.68 0.072 3.4 3475 F04 CDRH73-150 15 1.33 0.130 3.4
Figure 4. Operation above VIN(MAX). Output Ripple and Peak Inductor Current Increases
CDRH104R-150 15 3.1 0.050 4.0
Coilcraft
DO1606T-332 3.3 1.30 0.100 2.0
Inductor Selection and Maximum Output Current
DO1606T-472 4.7 1.10 0.120 2.0 A good fi rst choice for the inductor value is: DO1608C-332 3.3 2.00 0.080 2.9 1.2MHz DO1608C-472 4.7 1.50 0.090 2.9 L = (VOUT + VF )• f MOS6020-332 3.3 1.80 0.046 2.0 MOS6020-472 10 1.50 0.050 2.0 where VF is the voltage drop of the catch diode (~0.4V), DO3316P-103 10 3.9 0.038 5.2 f is the switching frequency and L is in μH. With this value DO3316P-153 15 3.1 0.046 5.2 the maximum load current will be above 1.6A at all duty cycles. The inductor’s RMS current rating must be greater The optimum inductor for a given application may differ than the maximum load current and its saturation current from the one indicated by this simple design guide. A larger should be at least 30% higher. For highest effi ciency, value inductor provides a higher maximum load current, and the series resistance (DCR) should be less than 0.15Ω. reduces the output voltage ripple. If your load is lower than Table 2 lists several vendors and types that are suitable. the maximum load current, then you can relax the value of the For robust operation at full load and high input voltages inductor and operate with higher ripple current. This allows (VIN > 30V), use an inductor with a saturation current you to use a physically smaller inductor, or one with a lower higher than 3.2A. DCR resulting in higher effi ciency. In addition, low inductance may result in discontinuous mode operation, which further reduces maximum load current. For details of maximum output current and discontinuous mode operation, see Linear Technology’s Application Note 44. Finally, for duty cycles greater than 50% (VOUT/VIN > 0.5), a minimum inductance is required to avoid sub-harmonic oscillations: 800kHz LMIN = (VOUT + VF )• f 3475fb 10