9.2.1.2.2 Inductor Selection

TI recommends you use the TPS63810 device with 0.47-µH inductors. For high efficiencies, use an inductor with a low DC resistance (DCR) and low core losses.

The saturation current of the inductor must be greater than the maximum inductor current in your application. To include sufficient margin for worst-case and transient operating conditions, TI recommends you use an inductor with saturation current that is at least 20% higher than the maximum inductor current in your application. The maximum current in the inductor occurs when the device operates in boost mode and the following is true:

• The input voltage is at its minimum value.
• The output voltage is at its maximum value.
• The output current is at its maximum value.

To calculate the maximum inductor current, first use Equation 1 to calculate the maximum duty cycle during boost operation (which is when the maximum inductor current occurs).

WHITESPACE

Equation 1.

where

• D is the duty cycle
• V_I is the input voltage
• V_O is the output voltage

WHITESPACE

WHITESPACE

Next, use Equation 2 to calculate the maximum inductor current.

Equation 2.

where

• I_LM is the peak inductor current
• I_O is the output current
• η is the converter efficiency (use the value from the application curves or assume 90%)
• D is the duty cycle (calculated with Equation 1)
• V_I is the input voltage
• f is the switching frequency (assume 2 MHz)
• L is the inductance (use 0.47 µH)

WHITESPACE

WHITESPACE

To include enough margin for transient conditions, TI recommends you use an inductor with a saturation current rating at least 20% higher than the calculated maximum current. In this example, TI recommends an inductor with a saturation current of at least 6.1 A.