CINmin= IOUT

4∙VPPMAX∙FSW

(34)

In the following table, some suitable capacitor part numbers are listed.

Manufacturer

Series

Size

Cap value (µF)

Rated voltage (V)

TDK

CGA5L3X5R1H106K160AB

1206

10

50

C3216X5R1H106K160AB

1206

10

50

Murata

GRT31CR61H106KE01

1206

10

50

8.4.2

Inductor selection

The inductor current ripple flowing into the output capacitor determines the output voltage ripple. Usually the

inductor value is selected in order to keep the current ripple lower than 20% - 40% of the output current over the

input voltage range. The inductance value can be calculated by the following equation:

∆IL=VIN−VOUT

L ∙TON=VOUTL∙TOFF

(35)

output current, the minimum inductance value can be calculated:

Lmin= VOUT

∆ILMAX∙1−Dmin

FSW

(36)

For those applications requiring higher inductor value for minimized current ripple, pay attention as the

maximum value must prevent the sub-harmonic instability given the designed internal slope compensation. As

a consequence the inductor value must satisfy the quality factor range:

0.4≤QP≤1.33

(37)

Where QP has been defined on the Section 7.1 GCO(s) control to output transfer function. The peak current

through the inductor is given by:

IL,PK=IOUT+∆IL2

(38)

So if the inductor value decreases, the peak current (that has to be lower than the current limit of the device)

increases. The higher the inductor value, the higher the average output current that can be delivered, without

reaching the current limit.

8.4.3

Output capacitor selection

The triangular shaped current ripple (with zero average value) flowing into the output capacitor gives the

output voltage ripple, which depends on the capacitor value and the equivalent resistive component (ESR).

Therefore, the output capacitor has to be selected in order to have a voltage ripple compliant with the application

requirements.

The voltage ripple equation can be calculated as:

∆VOUT=ESR∙∆IL,MAX+ ∆IL,MAX

8∙COUT∙FSW

(39)

For a ceramic (MLCC) capacitor, the capacitive component of the ripple dominates the resistive one. While for

an electrolytic capacitor the opposite is true. Neglecting the ESR contribution, the minimum value of the output

capacitor is given by:

COUT,min,RIPPLE= ∆IL,MAX

8∙∆VOUT∙FSW

(40)

L6982

Design of the power components

DS13683 - Rev 1

page 27/48