TPS54110−Q1

SLVS837 − JULY 2008

www.ti.com

8

APPLICATION INFORMATION

Figure 9 shows the schematic diagram for a typical TPS54110 application. The TPS54110 can provide up to 1.5 A of output

current at a nominal output voltage of 3.3 V. For proper thermal performance, the exposed PowerPAD under the device

must be soldered down to the printed-circuit board.

5

C3

+

RT

SYNC

SS/ENA

VBIAS

VIN

VIN

VIN

PGND

PGND

PGND

PwrPd

AGND

VSENSE

COMP

PWRGD

BOOT

PH

PH

PH

PH

PH

20

19

18

17

16

15

14

13

12

11

10

9

8

7

6

4

3

2

1

VIN (4.5 − 5.5 V)

C1

10

mF

R7

10 k

W

U2

TPS54110PWP

PWRGD

R4

71.5 k

W

C5

.047

mF

C4

0.1

mF

C9

10

mF

21

0.047

mF

R3

19.1 k

W

C7

33 pF

C6

2700 pF

C8

2200 pF

R5

2.05 k

W

R1

10.7 k

W

R2

3.92 k

W

12

L1

6.8

mH

3.3 V at 1.5 A

C2

100

mF

Figure 9. Application Schematic

DESIGN PROCEDURE

The following design procedure can be used to select

component values for the TPS54110. Alternately, the

SWIFT Designer Software can be used to generate a

complete design. The SWIFT Designer Software uses an

iterative design procedure to access a comprehensive

database of components when generating a design. This

section presents a simplified discussion of the design

process.

DESIGN PARAMETERS

The required parameters to begin the design process and

values for this design example are listed in Table 1.

Table 1. Design Parameters

DESIGN PARAMETER

EXAMPLE VALUE

Input voltage range

4.5 to 5.5 V

Output voltage

3.3 V

Input ripple voltage

100 mV

Output ripple voltage

30 mV

Output current rating

1.5 A

Operating frequency

700 kHz

As an additional constraint, the design is set up to be small

size and low component height.

SWITCHING FREQUENCY

The switching frequency is set within the range of 280 kHz

to 700 kHz by connecting a resistor from the RT pin to

AGND. Equation (1) is used to determine the proper RT

value.

RT(k

W) + 100

500 kHz

ƒ

s(kHz)

In this example, the timing-resistor value chosen for R4 is

71.5 k

Ω, setting the switching frequency to 700 kHz.

Alternately, the TPS54110 can be set to preprogrammed

switching frequencies of 350 kHz or 550 kHz by

connecting pins RT and SYNC as shown in Table 2.

Table 2. Selecting the Switching Frequency

FREQUENCY

RT

SYNC

350 kHz

Float

Float or AGND

550 kHz

Float

 2.5 V

(1)