ADVANCE INFORMATION for pre-production products; subject to change without notice.
The TPS6281x-Q1 is designed for a nominal 0.47-µH inductor with a switching frequency of typically 2.25 MHz. Larger values can be used to achieve a lower inductor current ripple but they may have a negative impact on efficiency and transient response. Smaller values than 0.47 µH will cause a larger inductor current ripple which causes larger negative inductor current in forced PWM mode at low or no output current. For a higher or lower nominal switching frequency, the inductance should be changed accordingly.
The inductor selection is affected by several effects like inductor ripple current, output ripple voltage, PWM-to-PFM transition point and efficiency. In addition, the inductor selected has to be rated for appropriate saturation current and DC resistance (DCR). Equation 8 calculates the maximum inductor current.
|TYPE||INDUCTANCE [µH]||CURRENT [A](1)||FOR DEVICE||NOMINAL SWITCHING FREQUENCY||DIMENSIONS [LxBxH] mm||MANUFACTURER(2)|
|XFL4015-471ME||0.47 µH, ±20%||3.5||TPS62813 / 12||2.25 MHz||4 x 4 x 1.6||Coilcraft|
|XEL4020-561ME||0.56 µH, ±20%||9.9||TPS62810 / 13 / 12||2.25 MHz||4 x 4 x 2.1||Coilcraft|
|XEL4030-471ME||0.47 µH, ±20%||12.3||TPS62810 / 13 / 12||2.25 MHz||4 x 4 x 3.1||Coilcraft|
|XEL3515-561ME||0.56 µH, ±20%||4.5||TPS62813 / 12||2.25 MHz||3.5 x 3.2 x 1.5||Coilcraft|
|XFL3012-331MEB||0.33 µH, ±20%||2.6||TPS62811 / 12||≥ 3.5 MHz||3 x 3 x 1.3||Coilcraft|
|XPL2010-681ML||0.68 µH, ±20%||1.5||TPS62811||2.25 MHz||2 x 1.9 x 1||Coilcraft|
|DFE252012F-R47M||0.47 µH, ±20%||see data sheet||TPS62813 / 12 / 11||2.25 MHz||2.5 x 2 x 1.2||Murata|
Calculating the maximum inductor current using the actual operating conditions gives the minimum saturation current of the inductor needed. A margin of about 20% is recommended to add. A larger inductor value is also useful to get lower ripple current, but increases the transient response time and size as well.