AAT1161 Datasheet, PDF (16/18 Pages) Advanced Analogic Technologies – 13.2V Input, 3A Step-Down Converter

DATA SHEET
AAT1161
13.2V Input, 3A Step-Down Converter
Input Capacitor
Input Ripple V_PP = 50mV
C_IN =
1
⎛
⎝
V_PP
I_LOAD
-
ESR^⎞⎠ · 4
· F_OSC
=
⎛ 50mV
⎝ 3A
1
- 5mΩ⎞⎠ · 4 · 800kHz
= 26µF; use 22µF
I = _RMS(MAX)
I_LOAD
2
=
1.5Arms
P = esr · I_RMS2 = 5mΩ · (1.5A)² = 11.25mW
AAT1161 Losses
Total losses can be estimated by calculating at the nominal input voltage (12V). All values assume an 85°C ambient
temperature and a 140°C junction temperature with the TDFN 50°C/W package.
R_DS(ON) = 0.18
t_SW = 5ms
I_Q = 300μA
P_LOSS
=
I_LOAD2
·
(R_DS(ON)
V_IN
·
V_OUT)
+ [(t_sw · F_OSC · I_LOAD + I_Q) · V_IN]
P_LOSS = 823mW
T_J(MAX) = T_AMB + Θ_JA · P_LOSS = 85°C + (50°C/W) · 0.823W = 126°C
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