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L5963

Application information

7.1

Output inductor (Lo)

The value of the output inductor (Lo) is usually calculated to satisfy the peak-to-peak ripple

current requirement. For the best compromise of cost, size and performance, it is suggested

to keep the inductor current ripple between 20% and 40% of the maximum current.

For example, if

IL = IRipple = 0.3 x IOUT(max).

Where, IOUT(max) is the maximum output current.

Then, the inductor value can be estimated by the following equation:

Equation 2

Where, fSW is the switching frequency, VIN(max) is the maximum input voltage.

If VOUT = 3.3 V, VIN(max) = 26 V, fSW = 250 kHz, IL = 0.3 x 3 A = 0.9 A

Equation 3

The next higher available value should be used, so L = 15 μH.

The peak current flowing in Inductor is IL(peak) = IOUT(max) + IL / 2.

If the Inductor value decreases, the peak current increases. The peak current has to be

lower than the current limit of the device.

An inductor having saturation current higher than the device current limit has to be chosen.

L5963 数据表(PDF) 29 Page - STMicroelectronics