DR73-4R7-R datasheet(17/19 Pages) SKYWORKS

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AAT1162

12V, 1.5A Step-Down DC/DC Converter

DATA SHEET

AAT1162 Losses

Total losses can be estimated by calculating the dropout (VIN = VO) losses where the power MOSFET RDS(ON) will be at

the maximum value. All values assume an 85°C ambient temperature and a 140°C junction temperature with the TDFN

37°C/W package.

PLOSS = ILOAD2 · RDS(ON)H = 1.5A2 · 0.158Ω = 0.355W

TJ(MAX) = TAMB + ΘJA · PLOSS = 85°C + (37°C/W) · 355mW = 96.6°C

The total losses are also investigated at the nominal input voltage (12V). The simplified version of the RDS(ON) losses

assumes that the N-channel and P-channel RDS(ON) are equal.

PTOTAL = ILOAD2 · RDS(ON) + [(tsw · FOSC · ILOAD + IQ) · VIN]

= 1.5A2 · 100mΩ + [(5ns · 800kHz · 1.5A + 150µA) · 12V] = 299mW

TJ(MAX) = TAMB + ΘJA · PLOSS = 85°C + (37°C/W) · 299mW = 96°C

DR73-4R7-R Datasheet(PDF) 17 Page - Skyworks Solutions Inc.