AAT2687 Datasheet, PDF (18/20 Pages) Advanced Analogic Technologies – PMIC Solution for 24V Systems with 2 High Performance Step-Down Converters

DATA SHEET
AAT2687
PMIC Solution for 24V Systems
with 2 High Performance Step-Down Converters
Channel 1 Current Limit
Voltage sense V_S = 100mV
Total trace parasitic resister and inductor DCR is 10mΩ
I_LIMIT = 5A.
I_PRESET =
V_S
DCR
=
100mV
10mΩ
= 10A > I_LIMIT
R₈ =
V_OUT · R₂
V_S - I_LIMIT · DCR
= ^{3.3V · 2kΩ} = 165kΩ
0.1V - 6A · 10mΩ
R₇ =
R₂ · R₈
R₈ - R₂
=
2kΩ · 165kΩ _{= 2kΩ}
165kΩ - 2kΩ
AAT2687 Losses
All values assume 25°C ambient temperature and thermal resistor of 50°C/W in the TQFN45-24 package.
P_TOTAL = I_OUT12 · R_DS(ON)H · D + (t_SW · F_S · I_OUT1 + I_Q) · V_IN1 + (V_IN2 - V_OUT2) · I_OUT2
P_TOTAL = ^{4.5A2 · 70mΩ · 3.3V} + (5ns · 490kHz · 4.5A + 70μA) · 12V + (3.3 - 1.8) · 600mA
12V
P_TOTAL = 1.42W
T_J(MAX) = T_AMB + Θ_JA · P_LOSS = 85°C + (33°C/W) · 1.42W = 131°C
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202033A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 8, 2012