Datasheet
6V to 42V
3.3V, 3.5A
1
BOOT
2
VIN
3
EN
4
RT/CLK
5
FB
6
COMP
7
GND
8
SW
9
PWRPD
U1
TPS54340DDA
C5
5600pF
R4
11.5k
C8
47pF
C4
0.1uF
L1
5.6uH
R6
10.2k
R5
31.6k
R3
162k
R1
365k
R2
86.6k
C1
2.2uF
C2
2.2uF
D1
B560C
C6
100uF
GND
FB
GND
GND
GND
VIN
FB
VOUT
GND
TPS54340
SLVSBK0B –OCTOBER 2012–REVISED MARCH 2014
www.ti.com
9 Application and Implementation
9.1 Application Information
The TPS54340 is a 42 V, 3.5 A, step down regulator with an integrated high side MOSFET. Idea applications
are: 12 V, 24 V Industrial, Automotive and Communications Power Systems.
9.2 Typical Application
Figure 36. 3.3 V Output TPS54340 Design Example
9.2.1 Design Requirements
This guide illustrates the design of a high frequency switching regulator using ceramic output capacitors. A few
parameters must be known in order to start the design process. These requirements are typically determined at
the system level. For this example, we will start with the following known parameters:
Table 1. Design Parameters
DESIGN PARAMETERS EXAMPLE VALUES
Output Voltage 3.3 V
Transient Response 0.875 A to 2.625 A load step ΔV
OUT
= 4 %
Maximum Output Current 3.5 A
Input Voltage 12 V nom. 6 V to 42 V
Output Voltage Ripple 0.5% of V
OUT
Start Input Voltage (rising VIN) 5.75 V
Stop Input Voltage (falling VIN) 4.5 V
9.2.2 Detailed Design Procedures
9.2.2.1 Selecting the Switching Frequency
The first step is to choose a switching frequency for the regulator. Typically, the designer uses the highest
switching frequency possible since this produces the smallest solution size. High switching frequency allows for
lower value inductors and smaller output capacitors compared to a power supply that switches at a lower
frequency. The switching frequency that can be selected is limited by the minimum on-time of the internal power
switch, the input voltage, the output voltage and the frequency foldback protection.
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