AAT1145 Datasheet, PDF (15/16 Pages) Advanced Analogic Technologies – 1.2A Step-Down Converter

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PRODUCT DATASHEET
AAT1145
1.2A Step-Down Converter
Input Capacitor
Input ripple V_PP = 25mV
1
1
C_IN(MIN) = _{⎛ VPP}
⎝ I_O
- ESR^⎞⎠ · 4 · f_S
=
= 15.4µF; use 22µF
⎛0.025
⎝ 1.2
-
0.01^⎞⎠
·4
· 1.5
· 10⁶
I_RMS =
I_O
2
= ^1.2 = 600mArms
2
P_CIN = ESR · I_RMS2 = 0.01 · 0.6² = 3.6mW
AAT1145 Losses
P_TOTAL = I_O2 · R_DS(ON)P · D + I_O2 · R_DS(ON)N · (1 - D) + (tSW · f_S · I_O) · V_IN
1.8
= 1.2² · 0.207 ·
4.2
+ 1.2² · 0.146 · ^⎛⎝1 -
1.8_⎞
4.2⎠
+
(5
·
10^-9
·
1.5
·
10⁶
·
1.2)
·
4.2
=
286mW
1145.2007.11.1.1
www.analogictech.com
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