TS2515

3A / 380KHz PWM Buck Converter

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Version: A09

Function Descriptions (Continue)

Input Capacitor Selection

For most designs, the operating inductor range is 15µH to 22µH. The inductor value can be derived from the following

equation:

Where is inductor Ripple Current. Large value inductors lower ripple current and small value inductors result in high

ripple currents. Choose inductor ripple current approximately 15% of the maximum load current 3A, ∆IL=0.45A. The

DC current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to

prevent core saturation (3A+0.45A).

Inductor Selection

The input current to the step-down converter is discontinuous, and so a capacitor is required to supply the AC current

to the step-down converter while maintaining the DC input voltage. A low-ESR capacitor is required to keep the noise

at the IC to a minimum. The low-ESR electrolytic capacitor may also suffice. The input capacitor value should be

greater than 470µF. However since it absorbs the input switching current it requires an adequate ripple current rating.

Its RMS current rating should be greater than approximately 1/2 of the DC load current. For insuring stable operation

CIN should be placed as close to the IC as possible. Alternately a smaller high quality ceramic 0.1uF capacitor may be

placed closer to the IC and a larger capacitor placed further away. If using this technique, it is recommended that the

larger capacitor be a electrolytic type.

Output Capacitor

The output capacitor is required to maintain the DC output voltage. Low ESR capacitors are preferred to keep the

output voltage ripple low. The characteristics of the output capacitor also affect the stability of the regulation control

system. The low-ESR electrolytic capacitors are recommended. The output capacitor value should be greater than

470µF.