AAT2689 Datasheet, PDF (18/20 Pages) Advanced Analogic Technologies – PMIC Solution for 12V Adapter Systems with 2-Output High Performance Step-Down Converters

PRODUCT DATASHEET
AAT2689
SystemPower^TM PMIC Solution for 12V Adapter Systems with 2-Output High Performance Step-Down Converters
Channel 1 Current Limit
Voltage sense V_S = 100mV
Total trace parasitic resistor and inductor DCR is 10mΩ
I_LIM =
V_{S =}
DCR
100mV
10mΩ
= 10A > 5A
R₈ =
V_OUT1 · R₂
=
V_OCP - I_LIMIT · DCR
3.3V · 2kΩ _{= 133kΩ}
0.1V - 5A · 10mΩ
R₇ =
R₂ · R₈
R₈ - R₂
=
2kΩ · 133kΩ
133kΩ - 2kΩ
= 2kΩ
AAT2689 Losses
All values assume a 25°C ambient temperature and thermal resistance of 50°C/W in the TDFN34-16 package.
P_TOTAL = I_OUT12 · R_DS(ON)H · D + (t_SW · F_S · I_OUT1 + I_Q1) · V_IN1 + (V_IN2 - V_OUT2) · I_OUT2
P_TOTAL = ^{2.5A2 · 70mΩ · 3.3V} + (5ns · 490kHz · 2.5A + 70μA) · 12V · (3.3V - 1.8V) · 600mA
12V
P_TOTAL = 1.1W
T_J(MAX) = T_AMB + Θ_JA · P_LOSS = 25°C + (50°C/W) · 1.1W = 80°C
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2689.2008.06.1.0