AAT2556 Datasheet, PDF (24/27 Pages) Advanced Analogic Technologies – Battery Charger and Step-Down Converter for Portable Applications

DATA SHEET
AAT2556
Battery Charger and Step-Down Converter for Portable Applications
Input Capacitor
Input Ripple V_PP = 25mV
1
1
C_IN = _{⎛ VPP}
⎝ I_O
- ESR^⎞⎠ · 4 · F_S
=
⎛ 25mV
⎝ 0.2A
= 1.38µF (use 4.7µF)
- 5mΩ⎞⎠ · 4 · 1.5MHz
I_RMS =
I_O
2
= 0.1Arms
P = esr · I_RMS2 = 5mΩ · (0.1A)² = 0.05mW
AAT2556 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
= ^{0.22 · (0.59Ω · 1.8V + 0.42Ω · [4.2V - 1.8V])}
4.2V
+ (5ns · 1.5MHz · 0.2A + 30µA) · 4.2V = 26.14mW
T_J(MAX) = T_AMB + Θ_JA · P_LOSS = 85°C + (50°C/W) · 26.14mW = 86.3°C
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202177B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013