Datasheet
Vout = 1.8 V, 3-A
R5
49.9
R6
10.0k
R3
4.22k
R4
0
C1
0.1uF
C3
10nF
C6
0.1uF
C9
22uF
C2
10uF
C4
8.2nF
C5
82pF
R2
45.3k
R1
66.5k
R7
8.06k
L1
2.2uH
C8
22uF
C7
470pF
1
BOOT
2
VIN
3
PH
4
GND
5
VSENS
6
COMP
7
EN
8
SS
9
PWPD
U1
TPS5432DDA
TPS5432
SLVSB89A –MARCH 2012–REVISED OCTOBER 2012
www.ti.com
APPLICATION INFORMATION
DESIGN GUIDE – STEP-BY-STEP DESIGN PROCEDURE
This example details the design of a high frequency switching regulator design using ceramic output capacitors.
This design is available as the TPS5432EVM-116 (PWR116) evaluation module (EVM). A few parameters must
be known in order to start the design process. These parameters are typically determined on the system level.
For this example, we start with the following known parameters:
Output Voltage 1.8 V
Transient Response 0.75 A to 2.25 A load step (25% to 75% ΔVout = 6%
maximum load)
Maximum Output Current 3 A
Input Voltage 3 V to 6V, 5 V nominal
Output Voltage Ripple < 18 mV p-p
Switching Frequency (Fsw) 700 kHz
The schematic diagram for this design example is shown in Figure 19 . The component reference designators of
this schematic are used for the equations in APPLICATION INFORMATION.
Figure 19. 1.8 V Output Power Supply Design with Adjustable UVLO
OUTPUT INDUCTOR SELECTION
The inductor selected works for the entire TPS5432 input voltage range. To calculate the value of the output
inductor, use Equation 5. K
IND
is a coefficient that represents the amount of inductor ripple current relative to the
maximum output current. The inductor ripple current is filtered by the output capacitor. Therefore, choosing high
inductor ripple currents impacts the selection of the output capacitor since the output capacitor must have a
ripple current rating equal to or greater than the inductor ripple current. In general, the inductor ripple value is at
the discretion of the designer; however, K
IND
is normally from 0.1 to 0.3 for the majority of applications.
For this design example, use K
IND
= 0.3 and the minimum inductor value is calculated to be 2.0 μH. For this
design, a nearest standard value was chosen: 2.2 μH. For the output filter inductor, it is important that the RMS
current and saturation current ratings not be exceeded. The RMS and peak inductor current can be found from
Equation 7 and Equation 8.
For this design, the RMS inductor current is 3.009 A and the peak inductor current is 3.409 A. The chosen
inductor is a TDK SPM6530T-2R2M. It has a saturation current rating 0f 8.4 A (20% inductance loss) and a RMS
current rating of 8.2 A (40 °C. temperature rise). The series resistance is 17.3 mΩ typical.
14 Submit Documentation Feedback Copyright © 2012, Texas Instruments Incorporated
Product Folder Links: TPS5432