TIDUF05 August 2022
Buck 2 and Buck 3 have a recommended inductor value of 1.0 µH. When selecting a component, it is important to verify the DC resistance and saturation current. The DC resistance of the inductance influences the efficiency of the converter directly – lower DC resistance is directly proportional to efficiency. The saturation requirement of the inductor is determined by combining the steady-state supply current and the inductor ripple current. The current rating needs to be sufficiently high but minimized as much as possible to reduce the physical size of the inductor. Calculate the inductor ripple current using Equation 3.
The parameters for the Buck 2 1.8-V rail include:
These parameters yield an inductor ripple current of ΔIL = 356 mA. Assuming a maximum load current of 1200 mA, Equation 4 can be used to calculate a minimum saturation current of 1400 mA.
The parameters for the Buck 3 1.2-V rail include:
These parameters yield an inductor ripple current of ΔIL = 332 mA. Assuming a maximum load current of 1200 mA, Equation 4 can be used to calculate a minimum saturation current of 1400 mA.
Buck 2 and Buck 3 of this design use the TDK® TFM201610ALMA1R0MTAA, which has a current rating of 3.1 A and a DC resistance of 60 mΩ. Additionally, this inductor has an operating temperature of –55°C to 150°C in a very small 2.0-mm × 1.6-mm package.