AAT2789 Datasheet, PDF (20/22 Pages) Advanced Analogic Technologies – Low Noise, High Frequency Dual Step-Down Converter

SystemPower^TM
PRODUCT DATASHEET
AAT2789
Low Noise, High Frequency Dual Step-Down Converter
AAT2789 Losses
Total loss can be estimated by calculating the dropout (V_IN = V_O) losses where the power MOSFETs R_{DS (ON)} will be at the
maximum value. All values assume an 85°C ambient temperature and a 120°C junction temperature with the TDFN
50°C/W package.
P_TOTAL = I_O12 · R_DS(ON)H1 + I_Q1 · V_IN1 + I_O22 · R_DS(ON)H2 + I_Q2 · V_IN2
P_TOTAL = 1.5A² · 120mΩ + 70µA · 4.2 + 0.5² · R_DS(ON)H2 + 70µA · 4.2V = 270mW
T_J(MAX)= T_AMB + Θ_JA · P_LOSS = 85°C + (50°C/W) · 270mW = 99°C
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2789.2008.03.1.0