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## CSD97370Q5M Datasheet(PDF) 11 Page - Texas Instruments

 Part No. CSD97370Q5M Description Synchronous Buck NexFET Power Stage Download 22 Pages Scroll/Zoom 100% Maker TI1 [Texas Instruments] Homepage http://www.ti.com Logo

## CSD97370Q5M Datasheet(HTML) 11 Page - Texas Instruments

 11 / 22 page 05101520253035404550020406080100120140Board Temperature ( C)°123CSD97370Q5Mwww.ti.comSLPS314A– JUNE 2011 – REVISED JUNE 2011Calculating Power Loss and SOAThe user can estimate product loss and SOA boundaries by arithmetic means (see the Design Example).Though the Power Loss and SOA curves in this datasheet are taken for a specific set of test conditions, thefollowing procedure will outline the steps engineers should take to predict product performance for any set ofsystem conditions.Design ExampleOperating Conditions: Output Current (lOUT) = 25A, Input Voltage (VIN ) = 7V, Output Voltage (VOUT) = 1V,Switching Frequency (fSW) = 800kHz, Output Inductor (LOUT) = 0.2µHCalculating Power Loss•Typical Power Loss at 25A = 3.5W (Figure 7)•Normalized Power Loss for switching frequency≈ 1.08 (Figure 12)•Normalized Power Loss for input voltage≈ 1.05 (Figure 13)•Normalized Power Loss for output voltage≈ 0.7 (Figure 14)•Normalized Power Loss for output inductor≈ 1.04 (Figure 15)•Final calculated Power Loss = 3.5W× 1.08 × 1.05 × 0.7 × 1.04 ≈ 2.89WCalculating SOA Adjustments•SOA adjustment for switching frequency≈ 2.6°C (Figure 12)•SOA adjustment for input voltage≈ 1.4°C (Figure 13)•SOA adjustment for output voltage≈ –1.0°C (Figure 14)•SOA adjustment for output inductor≈ 1.3°C (Figure 15)•Final calculated SOA adjustment = 2.6 + 1.4 + (–1.0) + 1.3 ≈ 4.3°CFigure 19. Power Stage CSD97370Q5M SOAIn the design example above, the estimated power loss of the CSD97370Q5M would increase to 2.89W. Inaddition, the maximum allowable board and/or ambient temperature would have to decrease by 4.3°C. Figure 19graphically shows how the SOA curve would be adjusted accordingly.1. Start by drawing a horizontal line from the application current to the SOA curve.2. Draw a vertical line from the SOA curve intercept down to the board/ambient temperature.3. Adjust the SOA board/ambient temperature by subtracting the temperature adjustment value.In the design example, the SOA temperature adjustment yields a reduction in allowable board/ambienttemperature of 4.3°C. In the event the adjustment value is a negative number, subtracting the negative numberwould yield an increase in allowable board/ambient temperature.Copyright© 2011, Texas Instruments Incorporated11