TS2515 Datasheet, PDF (4/7 Pages) Taiwan Semiconductor Company, Ltd – 3A / 380KHz PWM Buck Converter

TS2515
3A / 380KHz PWM Buck Converter
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.
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Version: A09