(

)

( )

(

)

(

)

(

)

-

´

=

+

´

´

´

IN

OUT

OUT

max

TRIP

IND peak

SW

IN

DS on

max

V

V

V

V

1

I

32 R

L f

V

(

)

(

)

(

)

(

)

(

)

(

)

(

)

-

´

-

´

=

´

=

´

´

´

IN

OUT

OUT

IN

OUT

OUT

max

max

SW

IN

OUT

SW

IN(max)

IND ripple

max

max

V

V

V

V

V

V

1

3

L

I

f

V

I

f

V

TPS53353

www.ti.com

SLUSAK2B – AUGUST 2011 – REVISED FEBRUARY 2015

Typical Applications (continued)

8.2.1.1 Design Requirements

Table 4. Design Parameters

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

INPUT CHARACTERISTICS

Voltage range

8

12

14

V

Maximum Input current

4.1

A

No load input current

1

mA

OUTPUT CHARACTERISTICS

Output voltage

1.5

V

Line regulation, 8 V

0.1%

Output voltage regulation

0.2%

A with FCCM

Output voltage ripple

20

Output load current

0

20

A

Output overcurrent

26

A

threshold

Soft-start time

1.4

ms

SYSTEMS CHARACTERISTICS

Switching frequency

500

kHz

Peak efficiency

91.87%

η

Full load efficiency

91.38%

Operating temperature

25

°C

8.2.1.2 Detailed Design Procedure

8.2.1.2.1

External Component Selection

Refer to the External Component Selection Using All Ceramic Output Capacitors section for guidelines for this

design with all ceramic output capacitors.

The external components selection is a simple process when using organic semiconductors or special polymer

output capacitors.

1. SELECT OPERATION MODE AND SOFT-START TIME

Select operation mode and soft-start time using Table 3.

2. SELECT SWITCHING FREQUENCY

Select the switching frequency from 250 kHz to 1 MHz using Table 1.

3. CHOOSE THE INDUCTOR

The inductance value should be determined to give the ripple current of approximately 1/4 to 1/2 of maximum

output current. Larger ripple current increases output ripple voltage and improves signal-to-noise ratio and

helps ensure stable operation, but increases inductor core loss. Using 1/3 ripple current to maximum output

current ratio, the inductance can be determined by Equation 8.

(8)

The inductor requires a low DCR to achieve good efficiency. It also requires enough room above peak

inductor current before saturation. The peak inductor current can be estimated in Equation 9.

(9)

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