Texas Instruments TPS54331 User manual

User’s Guide
TPS54331 Step-Down Converter Evaluation Module User's
Guide
Table of Contents
1 Introduction.............................................................................................................................................................................2
1.1 Background........................................................................................................................................................................ 2
1.2 Performance Specification Summary.................................................................................................................................2
1.3 Modifications...................................................................................................................................................................... 3
2 Test Setup and Results.......................................................................................................................................................... 4
2.1 Input / Output Connections................................................................................................................................................ 4
2.2 Efficiency............................................................................................................................................................................4
2.3 Output Voltage Load Regulation........................................................................................................................................ 5
2.4 Output Voltage Line Regulation......................................................................................................................................... 6
2.5 Load Transients..................................................................................................................................................................6
2.6 Loop Characteristics.......................................................................................................................................................... 7
2.7 Output Voltage Ripple........................................................................................................................................................ 7
2.8 Input Voltage Ripple........................................................................................................................................................... 8
2.9 Powering Up.......................................................................................................................................................................8
3 Board Layout.........................................................................................................................................................................10
3.1 Layout.............................................................................................................................................................................. 10
4 Schematic and Bill of Materials...........................................................................................................................................12
4.1 Schematic........................................................................................................................................................................ 12
4.2 Bill of Materials.................................................................................................................................................................13
5 Revision History................................................................................................................................................................... 13
List of Figures
Figure 2-1. TPS54331 Efficiency................................................................................................................................................. 4
Figure 2-2. TPS54331 Low Current Efficiency.............................................................................................................................5
Figure 2-3. TPS54331 Load Regulation...................................................................................................................................... 5
Figure 2-4. TPS54331 Line Regulation....................................................................................................................................... 6
Figure 2-5. TPS54331 Transient Response................................................................................................................................ 6
Figure 2-6. TPS54331 Loop Response....................................................................................................................................... 7
Figure 2-7. TPS54331 Output Ripple.......................................................................................................................................... 7
Figure 2-8. TPS54331 Input Ripple............................................................................................................................................. 8
Figure 2-9. TPS54331 Start-Up Relative to Vin...........................................................................................................................8
Figure 2-10. TPS5331 Start-up Relative to Enable..................................................................................................................... 9
Figure 3-1. Top-Side Layout...................................................................................................................................................... 10
Figure 3-2. Bottom-Side Layout (Looking From Top Side).........................................................................................................11
Figure 3-3. Top-Side Assembly..................................................................................................................................................11
Figure 4-1. TPS54331EVM-232 Schematic...............................................................................................................................12
List of Tables
Table 1-1. Input Voltage and Output Current Summary...............................................................................................................2
Table 1-2. TPS54331EVM-232 and Performance Specification Summary..................................................................................2
Table 1-3. Output Voltages Available...........................................................................................................................................3
Table 2-1. EVM Connectors and Test Points............................................................................................................................... 4
Table 4-1. TPS54331EVM-232 Bill of Materials.........................................................................................................................13
Trademarks
SWIFT™ is a trademark of Texas Instruments.
All trademarks are the property of their respective owners.
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TPS54331 Step-Down Converter Evaluation Module User's Guide 1
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1 Introduction
This user's guide contains background information for the TPS54331 as well as support documentation for
the TPS54331EVM-232 evaluation module (HPA232). Also included are the performance specifications, the
schematic, and the bill of materials for the TPS54331EVM-232.
1.1 Background
The TPS54331 dc/dc converter is designed to provide up to a 3-A output from an input voltage source of 3.5
V to 28 V. Rated input voltage and output current range for the evaluation module are given in Table 1-1.
This evaluation module is designed to demonstrate the small printed-circuit-board areas that may be achieved
when designing with the TPS54331 regulator. The switching frequency is internally set at a nominal 570 kHz.
The high-side MOSFET is incorporated inside the TPS54331 package along with the gate drive circuitry. The
low drain-to-source on resistance of the MOSFET allows the TPS54331 to achieve high efficiencies and helps
keep the junction temperature low at high output currents. The compensation components are external to the
integrated circuit (IC), and an external divider allows for an adjustable output voltage. Additionally, the TPS54331
provides adjustable slow start and undervoltage lockout inputs. The absolute maximum input voltage is 30 V for
the TPS54331EVM-232.
Table 1-1. Input Voltage and Output Current Summary
EVM INPUT VOLTAGE RANGE OUTPUT CURRENT RANGE
TPS54331EVM-232 VIN = 7 V to 28 V 0 A to 3 A
1.2 Performance Specification Summary
A summary of the TPS54331EVM-232 performance specifications is provided in Table 1-2. Specifications are
given for an input voltage of VIN = 15 V and an output voltage of 3.3V, unless otherwise specified. The
TPS54331EVM-232 is designed and tested for VIN = 10 V to 35 V. The ambient temperature is 25°C for all
measurements, unless otherwise noted.
Table 1-2. TPS54331EVM-232 and Performance Specification Summary
SPECIFICATION TEST CONDITIONS MIN TYP MAX UNIT
VIN voltage range 7 15 28 V
Output voltage set point 3.3 V
Output current range VIN = 7 V to 28 V 0 3 A
Line regulation IO = 1.5 A, VIN = 7 V – 28 V ±0.2%
Load regulation VIN = 14 V, IO = 0 A to 3 A ±0.15%
Load transient response IO = 0.75 A to 2.25 A Voltage change –100 mV
Recovery time 160 μs
IO = 2.25 A to 0.75 A Voltage change 100 mV
Recovery time 160 μs
Loop bandwidth VIN = 25 V, IO = 1 A 25.0 kHz
Phase margin VIN = 25 V , IO = 1 A 58 °
Input ripple voltage IO = 3 A 200 mVpp
Output ripple voltage IO = 3 A 10 mVpp
Output rise time 3.5 ms
Operating frequency 570 kHz
Maximum efficiency VIN = 10 V, VO = 5 V, IO = 0.75 A 91.6%
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1.3 Modifications
These evaluation modules are designed to provide access to the features of the TPS54331. Some modifications
can be made to this module.
1.3.1 Output Voltage Set Point
To change the output voltage of the EVMs, it is necessary to change the value of resistor R6. Changing the value
of R6 can change the output voltage above 0.8 V. The value of R6 for a specific output voltage can be calculated
using Equation 1.
R2 10 k 1.221 V
VO1.221 V
(1)
Table 1-3 lists the R6 values for some common output voltages. Note that VIN must be in a range so that the
minimum on-time is greater than 150 ns, and the maximum duty cycle is less than 93%. The values given in
Table 1-3 are standard values, not the exact value calculated using Table 1-3.
Table 1-3. Output Voltages Available
Output Voltage
(V)
R2 Value (kΩ)
1.8 8.25
2.5 4.75
3.3 3.24
5 1.96
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2 Test Setup and Results
This section describes how to properly connect, set up, and use the TPS54331EVM-232 and evaluation
modules. The section also includes test results typical for the evaluation modules and covers efficiency, output
voltage regulation, load transients, loop response, output ripple, input ripple, and start-up.
2.1 Input / Output Connections
The TPS54331EVM-232 is provided with input/output connectors and test points as shown in Table 2-1. A power
supply capable of supplying 3 A must be connected to J1 through a pair of 20 AWG wires. The load must
be connected to J4 through a pair of 20 AWG wires. The maximum load current capability must be 3 A. Wire
lengths must be minimized to reduce losses in the wires. Test-point TP1 provides a place to monitor the VIN
input voltages with TP2 providing a convenient ground reference. TP5 is used to monitor the output voltage with
TP6 as the ground reference.
Table 2-1. EVM Connectors and Test Points
REFERENCE
DESIGNATOR
FUNCTION
J1 VIN (see Table 1-1 for VIN range)
J2 2-pin header for enable. Connect EN to ground to disable, open to enable.
J3 2-pin header for slow start monitor and GND.
J4 VOUT, 3.3 V at 3-A maximum
TP1 VIN test point at VIN connector
TP2 GND test point at VIN
TP3 PH test point
TP4 Test point between voltage divider network and R3. Used for loop response measurements.
TP5 Output voltage test point at OUT connector
TP6 GND test point at OUT connector
2.2 Efficiency
The efficiency of this EVM peaks at a load current of about 0.6 A - 1 A and then decreases as the load
current increases towards full load. Figure 2-1 shows the efficiency for the TPS54331EVM-232 at an ambient
temperature of 25°C.
0
10
20
30
40
50
60
70
80
90
100
0 0.5 11.5 22.5 3
I - Output Current - A
O
Efficiency - %
V = 7 V
IN
V = 14 V
IN
V = 21 V
IN
V = 28 V
IN
Figure 2-1. TPS54331 Efficiency
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Figure 2-2 shows the efficiency for the TPS54331EVM-232 at lower output currents between 0.01 A and 0.20 A
at an ambient temperature of 25°C.
0
10
20
30
40
50
60
70
80
90
100
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2
I - Output Current - A
O
Efficiency - %
V = 7 V
IN V = 14 V
IN
V = 21 V
IN
V = 28 V
IN
Figure 2-2. TPS54331 Low Current Efficiency
The efficiency may be lower at higher ambient temperatures, due to temperature variation in the drain-to-source
resistance of the MOSFETs.
2.3 Output Voltage Load Regulation
The load regulation for the TPS54331EVM-232 is shown in Figure 2-3.
0.9985
0.999
0.9995
1
1.0005
1.001
1.0015
1.002
1.0025
1.003
1.0035
1.004
0 0.5 1 1.5 2 2.5 3 3.5
V = 14 V
IN
V = 21 V
IN
V = 28 V
IN
V = 7 V
IN
I - Output Current - A
O
Output Regulation - %
Figure 2-3. TPS54331 Load Regulation
Measurements are given for an ambient temperature of 25°C.
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2.4 Output Voltage Line Regulation
The line regulation for the TPS54331EVM-232 is shown in Figure 2-4.
V Output Voltage - V
O-
3.28
3.29
3.3
3.31
3.32
3.33
3.34
3.35
3.36
3.37
3.38
0 5 10 15 20 25 30
V - Input Voltage -V
I
I = 0 A
O
I = 1.5 A
O
I = 3 A
O
Figure 2-4. TPS54331 Line Regulation
2.5 Load Transients
The TPS54331EVM-232 response to load transients is shown in Figure 2-5. The current step is from 25% to
75% of maximum rated load. Total peak-to-peak voltage variation is as shown, including ripple and noise on the
output.
VOUT
Output Current
t - Time - 200 s/divm
Figure 2-5. TPS54331 Transient Response
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2.6 Loop Characteristics
The TPS54331EVM-232 loop-response characteristics are shown in Figure 2-6 . Gain and phase plots are
shown for VIN voltage of 15 V. Load current for the measurement is 1.5 A.
-30
-20
-10
0
10
20
30
40
50
60
70
f - Frequency - Hz
-90
-60
-30
0
30
60
90
120
150
180
210
Phase - deg
10 100 1k 10k 100k 1M
Gain - dB
Figure 2-6. TPS54331 Loop Response
2.7 Output Voltage Ripple
The TPS54331EVM-232 output voltage ripple is shown in Figure 2-7 . The output current is the rated full load of
3 A. Voltage is measured directly across output capacitors.
VOUT
PH
t - Time - 1 s/divm
Figure 2-7. TPS54331 Output Ripple
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2.8 Input Voltage Ripple
The TPS54331EVM-232 input voltage ripple is shown in Figure 2-8 . The output current for each device is at full
rated load of 3 A.
VIN
PH
t - Time - 1 s/divm
Figure 2-8. TPS54331 Input Ripple
2.9 Powering Up
The start-up waveform is shown in Figure 2-9 and Figure 2-10. In Figure 2-9, the top trace shows Vin, and the
bottom trace shows Vout. InFigure 2-9 , the top trace shows EN (enable) whereas the bottom trace shows Vout.
Initially, the input voltage is applied and the output is inhibited by using a jumper at J2 to tie EN to GND. When
the jumper is removed, EN is released. When the EN voltage reaches the enable-threshold voltage of 1.25 V, the
start-up sequence begins and the internal reference voltage begins to ramp up at the internally set rate toward
0.8 V and the output voltage ramps up to the externally set value of 3.3 V.
VIN
VOUT
t - Time - 5 ms/div
Figure 2-9. TPS54331 Start-Up Relative to Vin
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ENA
VOUT
t - Time - 5 ms/div
Figure 2-10. TPS5331 Start-up Relative to Enable
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3 Board Layout
This section provides a description of the TPS54331EVM-232, board layout, and layer illustrations.
3.1 Layout
The board layout for the TPS54331EVM-232 and is shown in Figure 3-1 through Figure 3-3. The topside layer of
the EVM is laid out in a manner typical of a user application. The top and bottom layers are 2-oz. copper.
The top layer contains the main power traces for VIN, OUT, and VPHASE. Also on the top layer are connections
for the remaining pins of the TPS54331 and a large area filled with ground. The bottom layer contains ground
and a signal route for the BOOT capacitor. The top and bottom and internal ground traces are connected with
multiple vias placed around the board including four vias directly under the TPS54331 device to provide a
thermal path from the top-side ground traces to the bottom-side ground plane.
The input decoupling capacitors (C1, C2, and C3) and bootstrap capacitor (C4) are all located as close to the
IC as possible. In addition, the voltage set-point resistor divider components are also kept close to the IC. The
voltage divider network ties to the output voltage at the point of regulation, the copper Vout trace past the output
capacitor C3. For the TPS54331, an additional input bulk capacitor may be required, depending on the EVM
connection to the input supply.
Figure 3-1. Top-Side Layout
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