Rev.P6

7

VPN12AD1E-FU

APPLICATIONS INFORMATION: (Cont.)

Selecting the Input Capacitor:

The input requires a capacitor to supply the AC ripple current to the inductor, while limiting noise at the

input source. Use a low-ESR capacitor with a value >6.8μF to minimize the Module noise. Ceramic

capacitors are preferred, low-ESR electrolytic capacitors can also suffice. However since it absorbs the

input switching current it requires an adequate ripple current rating. Use a capacitor with an RMS

current rating greater than the inductor ripple current.

To ensure stable operation, place the input capacitor as close to the Module as possible. As an

alternative, place a small, high-quality ceramic 0.1μF capacitor close to the Module and place the larger

capacitor further away. If using the latter technique, electrolytic type capacitors for the larger capacitor.

Place all ceramic capacitors close to the VPN12AD1E-FU.

Selecting the Output Capacitor:

The output capacitor maintains the DC output voltage. For best results, use low-ESR capacitors to

minimize the output voltage ripple. The output capacitor’s characteristics also affect regulatory control

system’s stability. For best results, use ceramic or low-ESR electrolytic capacitors. For ceramic

capacitors, the capacitance dominates the impedance at the switching frequency, and so the output

voltage ripple is mostly independent of the ESR. The min. output capacitance is estimated as below

formula, (Please also consider the bias voltage impacted the capacitance changing)

output capacitance.

Choose an output capacitor that satisfies the output ripple and load transient requirements of the

design. 6.8μF-to-22μF ceramic capacitance is suitable for most applications. (Please also consider the

bias voltage impacted the capacitance changing)