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SD3814-1R2-R Datasheet, PDF (2/4 Pages) Cooper Bussmann, Inc. – Switching Regulators | |||
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Inductor Selection: Buck Converters
Switch
Buck
Inductor
12V
Input
Voltage
Freewheeling
Diode
Output
Cap
5V
Output
Voltage
Inductor Selection: Boost Converters
Boost
Inductor
Diode
5V
Input
Voltage
Switch
Output
Cap
12V
Output
Voltage
Figure 2:
Buck Inductor Example
Figure 2 Application Parameters:
⢠Switching frequency= 250kHz
⢠Input voltage range= 12V±10%
⢠Max ripple current = 220mA
⢠Output Voltage= 5.0V
Step 1. Calculate the Duty Cycle
⢠Vo = output voltage
⢠Vi = Max input voltage
⢠D = Vo / Vi
⢠D = 5/13.2 = 0.379
Step 2. Calculate the Voltage Across the Inductance
⢠V1 = Vi-Vo (Switch on)
⢠V1 = 13.2 - 5 = 8.2V
⢠V1 = -Vo (Switch off)
⢠V1 = - Vo = - 5V
Step 3. Calculate the Required Inductance
⢠L = Vl.dt/di
⢠L = (8.2 x 0.379/250 x 103)/0.22
⢠L = 56μH
Figure 3:
Boost Inductor Example
Figure 3 Application Parameters:
⢠Switching frequency= 100kHz
⢠Input voltage range= 4.5-5.5V
⢠Max ripple current = 100mA
⢠Output Voltage= 12.0V
Step 1. Calculate the Duty Cycle:
⢠Vo= output voltage
⢠Vi = Max input voltage
⢠D = 1 - (Vi / Vo)
⢠D = 1 â (5.5/12.0) = 0.542
Step 2. Calculating the voltage across the inductance
⢠V1 = Vi (Switch on)
⢠V1 = 5.5V
⢠V1 = Vo â Vi (Switch off)
⢠V1 = 12 â 5.5 = 6.5V
Step 3. Calculating the required inductance
⢠L = Vl.dt/di
⢠L= (5.5 x 0.542/100 x 103)/0.1
⢠L= 298μH
Typical Applications Using Inductors for Switching Regulators
Media Players
Industrial Test Equipment
Digital Cameras
Laptop Computers
Backlight Displays
Mobile Phones
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