SPSB100 datasheet(109/213 Pages) STMICROELECTRONICS

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ΔIL=IRipple=0.3IOUTMAX

(1)

Where IOUT(MAX) is the maximum output current.

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

L> 1fSWXΔILXVOUTX1− VOUTVINMAX

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

The peak current flowing in the inductor is: ILPEAK=IOUTMAX+ΔIL2

If the inductor value decreases, the peak current increases. The peak current has to be lower than the current

limit of the device. The inductor should have a saturation current higher than the device current limit.

Note:

To meet slope compensation, L needs to meet the following equation:

L>12XVOUTIslope

With Islope = 650 mA × fSW.

8.2.2

BUC3 inductor

The value of the output inductor 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 maximum load current.

For example, if:

ΔIL=IRipple=0.3IOUTMAX

(2)

Where IOUT(MAX) is the maximum output current.

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

L> 1fSWXΔILXVOUTX1− VOUTVINMAX

(3)

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

The peak current flowing in the inductor is:

ILPEAK =IOUTMAX+ΔIL2

(4)

If the inductor value decreases, the peak current increases. The peak current has to be lower than the current

limit of the device. The inductor should have a saturation current higher than the device current limit.

Note:

To meet slope compensation, L needs to meet the following equation:

L>12XVOUTIslope

(5)

With Islope = 325 mA × fSW.

SPSB100

Application circuit

DS14640 - Rev 2

page 109/213

SPSB100 Scheda tecnica(PDF) 109 Page - STMicroelectronics