Datasheet
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 kW
U2
TPS54110PWP
PWRGD
R4
71.5 kW
C5
.047 mF
C4
0.1 mF
C9
10 mF
21
0.047 mF
R3
19.1 kW
C7
33 pF
C6
2700 pF
C8
2200 pF
R5
2.05 kW
R1
10.7 kW
R2
3.92 kW
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(kW) +
100 500 kHz
ƒ
s(kHz)
In this example, the timing-resistor value chosen for R4 is
71.5 kΩ, 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)