AAT1149A Datasheet, PDF (14/17 Pages) Advanced Analogic Technologies – 2.2MHz Fast Transient 400mA Step-Down Converter

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PRODUCT DATASHEET
AAT1149A
2.2MHz Fast Transient 400mA Step-Down Converter
Input Capacitor
Input Ripple V_PP = 10mV
C_IN =
1
=
V_PP
I_O
- ESR
· 4 · F_S
I_RMS =
I_O
2
= 0.2Arms
1
= 5.7µF; use 4.7µF
10mV
0.4A
- 5mΩ
· 4 · 2.2MHz
P = esr · I_RMS2 = 5mΩ · (0.2A)² = 0.2mW
AAT1149A Losses (WLCSP-5 Package)
P_TOTAL
=
I_O2
·
(R_DS(ON)H
·
V_O
+ R_DS(ON)L
V_IN
·
[V_IN
-V_O])
+ (t_sw · F_S · I_O + I_Q) · V_IN
0.4² · (0.725Ω · 1.875V + 0.7Ω · [4.2V - 1.875V])
=
4.2V
+ (5ns · 2.2MHz · 0.4A + 3mA) · 4.2V = 149mW
T_J(MAX) = T_AMB + Θ_JA · P_LOSS = 85°C + (284°C/W) · 149mW = 127°C
14
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1149A.2008.08.1.1