AAT1147 Datasheet, PDF (16/18 Pages) Advanced Analogic Technologies – High Efficiency, Low Noise, Fast Transient 400mA Step-Down Converter

DATA SHEET
AAT1147
High Efficiency, Low Noise, Fast Transient 400mA Step-Down Converter
Input Capacitor
Input Ripple V_PP = 25mV
1
1
C_IN = _{⎛ VPP}
⎝ I_O
- ESR^⎞⎠ · 4 · F_S
=
⎛ 25mV
⎝ 0.4A
= 3.11μF; use 4.7μF
- 5mΩ⎞⎠ · 4 · 1.4MHz
I_RMS =
I_O
2
= 0.2Arms
P = esr · I_RMS2 = 5mΩ · (0.2A)² = 0.2mW
AAT1147 Losses
P_TOTAL
=
I_O2
·
(R_DSON(H)
·
V_O + R_DSON(L)
V_IN
·
[V_IN
-V_O])
+ (t_sw · F_S · I_O + I_Q) · V_IN
T_J(MAX) = T_AMB + Θ_JA · P_LOSS = 85°C + (160°C/W) · 126mW = 105.1°C
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201986A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 23, 2012