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| AAT1275_08 Datasheet, PDF (16/19 Pages) Advanced Analogic Technologies – Boost Converter with USB Power Switch | |||
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SwitchRegTM
PRODUCT DATASHEET
AAT1275
Boost Converter with USB Power Switch
Step-Up Converter Design Example
Specifications
VOUT = 5V
IOUT = 300mA
VIN = 2.7V to 4.2V (3.6V nominal)
TAMB = 50°C
Output Inductor
DMAX =
VOUT - VIN(MIN)
VOUT
=
5V - 2.7V
5V
= 0.46
From the characterization curves, the switching frequency at room temperature with a 300mA load and 2.2µH inductor
is about 800kHz.
IPP
=
VIN(MIN) · DMAX
L · FS
IP
=
IO
1-D
IPK = IP +
IPP
2
IV = IP - IPP
IV = IP - IPP = 0.9A - 0.7A = 0.20A
IRMS =
IPK2 + IPK · IV + IV2 =
3
0.9A2 + 0.9A · 0.2A + 0.2A2 = 0.59A
3
For the Sumida CDRH2D14-2R2 inductor, ISAT = 1.0A, IDC(MAX) = 1.6A and DCR = 94mâ¦.
PLOSS(INDUCTOR) = I2RMS · DCR = (590mA)2 · 94m⦠= 32mW
5V Output Capacitor
âVOUT = 0.05V
COUT(MIN) =
IOUT · DMAX
FS · âVOUT
=
0.3A · 0.46
800kHz · 0.05V
= 3.0µF; use 4.7µF 10V MLC
16
www.analogictech.com
1275.2008.04.1.7
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