Data Sheet

LT7200S

analog.com

Rev 0

27 of 35

CSS = 20nF

Use a typical 22nF capacitor for CSS.

Because efficiency is important at both high and low load current, discontinuous mode operation is utilized. Select

from the characteristic curves the correct RT resistor for the 1MHz switching frequency. Based on that, RRT should be

100kΩ. Then calculate the inductor value to achieve a current ripple that is about 40% of the maximum peak current

limit (5A) at maximum VIN:

L =

VOUT

f x ∆IL

x (1 −

VOUT

VIN

)

L =

1.2V

1MHz x 2A

x (1 −

1.2V

15V

) = 0.55μH

The closest standard value inductor higher is 0.6μH.

Select COUT based on the ESR required to satisfy the output ripple requirement and the bulk capacitance needed for

loop stability. For this design, use two 47μF ceramic capacitors.

Size CIN for a maximum current rating of:

IRMS_Channel = 5A x (

1.2V

15V

)√(

15V

1.2V

− 1) = 1.36A

IRMS_Total = 36A x 4 = 5.4A, if connect outputs of four channels together.

Decoupling VIN with two 22μF ceramic capacitor, as shown in Figure 38, is adequate for most applications.