AAT2506
1MHz Step-Down Converter/LDO Regulator
Input Capacitor
Input Ripple VPP = 25mV
1
1
CIN =
=
= 4.75µF
⎛
VPP
⎞
⎠
⎛ 25mV
⎝ 0.4A
⎞
- ESR · 4 · FS
- 5mΩ · 4 · 1MHz
⎝ IOBUCK
⎠
IOBUCK
IRMS
=
= 0.2Arms
2
P = esr · IRMS2 = 5mΩ · (0.2A)2 = 0.2mW
AAT2506 Losses
IOBUCK2 · (RDSON(HS) · VOBUCK + RDSON(LS) · [VIN - VOBUCK])
PTOTAL
=
VIN
+ (tsw · F · IOBUCK + IQBUCK + IQLDO) · VIN + (VIN - VLDO) · ILDO
0.42 · (0.725Ω · 1.8V + 0.7Ω · [4.2V - 1.8V])
4.2V
=
+ (5ns · 1.0MHz · 0.4A + 50µA +125µA) · 4.2V + (4.2V - 3.3V) · 0.3A = 392mW
TJ(MAX) = TAMB + ΘJA · PLOSS = 85°C + (50°C/W) · 392mW = 105°C
2506.2005.12.1.0
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