ISL98607

4. Application Information

FN8421 Rev.1.00

Page 22 of 29

Jun.3.19

4.16 Component Selection

The design of the boost converter is simplified by an internal compensation scheme, which allows easy system

design without complicated calculations. Select component values using the following recommendations.

4.16.1 Input Capacitor

Renesas recommends that a 10µF X5R/X7R or equivalent ceramic capacitor is placed on the VIN input supply.

4.16.2 Inductor

First, determine the minimum inductor saturation current required for the application.

The ISL98607 operates in Continuous Conduction Mode (CCM) at higher load current, and in Discontinuous

Conduction Mode (DCM) and PFM mode at lighter loads.

In CCM, you can calculate the peak inductor current using Equations 4 through 8.

Given these parameters:

• Input Voltage = VIN

• Output Voltage = VO

• Duty Cycle = D

• Switching Frequency = fSW

•tSW =1/fSW

Then the inductor ripple can be calculated as:

where D = 1 - (VIN/VO), then rewrite Equation 4:

The average inductor current is equal to the average input current, where IIAVG can be calculated from the

efficiency of the converter.

To find the peak inductor current write the expression as:

Substituting Equations 5 and 6 in Equation 7 calculates IPk.

Example:

Consider the following parameters in the steady-state boost regulator operating in CCM mode.

•VIN =2.5V

•VO =5.3V

•fSW =1.45MHz

IP-P

VIN

 D



=

L





f

SW

V

O 

(EQ. 4)

IP-P

VIN

 VO VIN

–



=

L





f

SW

V

O 

(EQ. 5)

IIAVG

VOIO

 VINEfficiency





=

(EQ. 6)

IPk IP-P 2



=

IIAVG

+

(EQ. 7)

IPK

0.5VIN VO VIN

–

L

 fSWVO VO



I

O 

+



V

 INEFF





=

(EQ. 8)