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Table of Contents
User’s Guide
TPS56628 Buck Converter Evaluation Module User's
Guide
ABSTRACT
This user's guide contains information for the TPS56628EVM-534 evaluation module (EVM) as well as for
the TPS56628. Included are the performance specifications, schematic, and the bill of materials of the
TPS56628EVM-534.
Table of Contents
1 Introduction.............................................................................................................................................................................2
2 Performance Specification Summary................................................................................................................................... 3
3 Modifications...........................................................................................................................................................................4
3.1 Output Voltage Setpoint..................................................................................................................................................... 4
3.2 Output Filter and Closed-Loop Response..........................................................................................................................4
4 Test Setup and Results.......................................................................................................................................................... 5
4.1 Input and Output Connections........................................................................................................................................... 5
4.2 Start-Up Procedure............................................................................................................................................................ 5
4.3 Efficiency............................................................................................................................................................................6
4.4 Load Regulation................................................................................................................................................................. 7
4.5 Line Regulation.................................................................................................................................................................. 8
4.6 Load Transient Response.................................................................................................................................................. 8
4.7 Output Voltage Ripple........................................................................................................................................................ 9
4.8 Input Voltage Ripple......................................................................................................................................................... 10
4.9 Start-Up............................................................................................................................................................................ 11
4.10 Shut-Down..................................................................................................................................................................... 12
5 Board Layout.........................................................................................................................................................................13
5.1 Layout.............................................................................................................................................................................. 13
6 Schematic, Bill of Materials, and Reference...................................................................................................................... 15
6.1 Schematic........................................................................................................................................................................ 15
6.2 Bill of Materials.................................................................................................................................................................16
6.3 Reference.........................................................................................................................................................................16
7 Revision History................................................................................................................................................................... 16
Trademarks
D-CAP2™ and Eco-mode™ are trademarks of Texas Instruments.
All trademarks are the property of their respective owners.
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Introduction
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1 Introduction
The TPS56628 is a single, adaptive on-time, D-CAP2™-mode, synchronous buck converter requiring a low
external component count. The D-CAP2 control circuit is optimized for low-ESR output capacitors such as
POSCAP, SP-CAP, or ceramic types and features fast transient response with no external compensation. The
switching frequency is internally set at a nominal 650 kHz. Pulse skipping Eco-mode™ operation improves
efficiency under light load conditions. The high-side and low-side switching MOSFETs are incorporated inside
the TPS56628 package along with the gate-drive circuitry. The low drain-to-source on-resistance of the
MOSFETs allows the TPS56628 to achieve high efficiencies and helps keep the junction temperature low at
high-output currents. The TPS56628 dc/dc synchronous converter is designed to provide up to a 6-A output from
an input voltage source of 4.5 V to 18 V. The output voltage range is from 0.6 to 5.5 V. Rated input voltage and
output current range for the evaluation module are given in Table 1-1.
The TPS56628EVM-534 evaluation module circuit is a single, synchronous buck converter providing 1.05 V at 6
A, from 4.5-V to 18-V input. This user’s guide describes the TPS56628EVM-534 performance.
Table 1-1. Input Voltage and Output Current Summary
2
EVM
Input Voltage Range
Output Current Range
TPS56628EVM-534
VIN = 4.5 to 18 V
0 to 6 A
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Performance Specification Summary
2 Performance Specification Summary
A summary of the TPS56628EVM-534 performance specifications is provided in Table 2-1. Specifications are
given for an input voltage of VIN = 12 V and an output voltage of 1.05 V, unless otherwise noted. The ambient
temperature is 25°C for all measurement, unless otherwise noted.
Table 2-1. TPS56628EVM-534 Performance Specifications Summary
SPECIFICATIONS
TEST CONDITIONS
Input voltage range (VIN)
MIN
TYP
MAX
4.5
12
18
Output voltage
Operating frequency
VIN = 12 V, IO = 3 A
Output current range
UNIT
V
1.05
V
650
kHz
0
6
A
Line regulation
IO = 2.5 A
±0.4
%
Load regulation
VIN = 12 V
+1.22 or –
0.10
%
Overcurrent limit
VIN = 12 V, LO = 1.5 µH
Output ripple voltage
VIN = 12 V, IO = 6 A
Maximum efficiency
VIN = 5 V, IO= 1 A
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6.6
7.3
20
88.2
8.9
A
mVPP
%
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Modifications
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3 Modifications
These evaluation modules are designed to provide access to the features of the TPS56628. Some modifications
can be made to this module.
3.1 Output Voltage Setpoint
To change the output voltage of the EVMs, change the value of resistor R1. Changing the value of R1 can
change the output voltage more than 0.8 V. The value of R1 for a specific output voltage can be calculated using
Equation 1.
For output voltage from 0.8 to 5.5 V:
æ R1 ö
VO = 0.765 ´ ç 1+
÷
è R2 ø
(1)
Table 3-1 lists the R1 values for some common output voltages. An option feed-forward capacitor (C4) may be
used to improve phase margin. Pads for this component (C4) are provided on the printed-circuit board (PCB).
Note that the resistor values given in Table 3-1 are standard values and not the exact value calculated using
Equation 1.
Table 3-1. Output Voltages
Output
Voltage
(V)
(1)
C4 (pF)(1)
R1 (kΩ) R2 (kΩ)
MIN
TYP
L1 (µH)
MAX
MIN
C9 + C10 + C11 (µF)
TYP
MAX
MIN
MAX
1
6.81
22.1
5
150
220
1.0
1.5
4.7
20
68
1.05
8.25
22.1
5
150
220
1.0
1.5
4.7
20
68
1.2
12.7
22.1
5
100
1.0
1.5
4.7
20
68
1.5
21.5
22.1
5
68
1.0
1.5
4.7
20
68
1.8
30.1
22.1
5
22
1.2
1.5
4.7
20
68
2.5
49.9
22.1
5
22
1.5
2.2
4.7
20
68
3.3
73.2
22.1
2
22
1.8
2.2
4.7
20
68
5
124
22.1
2
22
2.5
3.3
4.7
20
68
Optional
3.2 Output Filter and Closed-Loop Response
The TPS56628 relies on the output filter characteristics to ensure stability of the control loop. Table 3-1 shows
the recommended output filter components for common output voltages. It is possible for other output filter
component values to provide acceptable closed-loop characteristics. R3 and TP4 are provided for convenience
in breaking the control loop and measuring the closed-loop response.
4
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Test Setup and Results
4 Test Setup and Results
This section describes how to properly connect, set up, and use the TPS56628EVM-534. This section also
includes test results typical for the evaluation modules and efficiency, output load regulation, output line
regulation, load transient response, output voltage ripple, input voltage ripple, start-up, and switching frequency.
4.1 Input and Output Connections
The TPS56628EVM-534 is provided with input and output connectors and test points as shown in Table 4-1. A
power supply capable of supplying 2 A must be connected to J1 through a pair of 20-AWG wires. The load must
be connected to J2 through a pair of 20-AWG wires. The maximum load current capability is
6 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. TP8 is used to monitor the output
voltage with TP9 as the ground reference.
Table 4-1. Connection and Test Points
Reference Designator
Function
J1
VIN (see Table 1-1 for VIN range)
J2
VOUT, 1.2 V at 5-A maximum
JP1
EN control. Connect EN to OFF to disable, connect EN to ON to enable
TP1
VIN test point at VIN connector
TP2
GND test point at VIN connector
TP3
EN test point
TP4
Power good (PG) test point
TP5
Switch node test point
TP6
Analog ground test point
TP7
Power ground test point
TP8
Output voltage test point at VOUT connector
TP9
Ground test point at VOUT connector
4.2 Start-Up Procedure
1. Ensure that the jumper at JP1 (Enable control) is set from EN to OFF.
2. Apply appropriate VIN voltage to VIN and PGND terminals at J1.
3. Move the jumper at JP1 (Enable control) to cover EN and ON. The EVM enables the output voltage.
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Test Setup and Results
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4.3 Efficiency
Figure 4-1 shows the efficiency for the TPS56628EVM-534 at an ambient temperature of 25°C.
100
90
80
Efficiency - %
70
VIN = 5 V
60
VIN = 12 V
50
40
30
20
10
0
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
5.00
5.50
6.00
Output Current - A
C001
Figure 4-1. EFFICIENCY vs OUTPUT CURRENT
Figure 4-2 shows the efficiency at light loads for the TPS56628EVM-534 at an ambient temperature of 25°C.
100
90
80
Efficiency - %
70
60
VIN = 12 V
50
VIN = 5 V
40
30
20
10
0
0.001
0.01
0.1
1
10
Output Current - A
C002
Figure 4-2. EFFICIENCY vs OUTPUT CURRENT
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Test Setup and Results
4.4 Load Regulation
The load regulation for the TPS56628EVM-534 is shown in Figure 4-3.
1.50
VIN = 5 V
1.00
Load Regulation - %
VIN = 12 V
0.50
0.00
±0.50
±1.00
±1.50
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
Output Current - A
C003
Figure 4-3. LOAD REGULATION vs OUTPUT CURRENT
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Test Setup and Results
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4.5 Line Regulation
The line regulation for the TPS56628EVM-534 is shown in Figure 4-4.
0.5
0.4
0.3
Line Rgulation - %
0.2
IOUT = 3 A
0.1
0
-0.1
-0.2
-0.3
-0.4
-0.5
4
6
8
10
12
14
16
18
Input Voltage - V
C004
Figure 4-4. LINE REGULATION vs INPUT VOLTAGE
4.6 Load Transient Response
The TPS56628EVM-534 response to load transient is shown in Figure 4-5. The current step is from 1.5 A to 4.5
A. Total peak-to-peak voltage variation is as shown.
VOUT = 50 mV / div (ac coupled)
IOUT = 2 A / div
Load step = 1.5 - 4.5 A, slew rate = 500 mA / µsec
Time = 200 µsec / div
Figure 4-5. TPS56628EVM-534 Load Transient Response
8
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Test Setup and Results
4.7 Output Voltage Ripple
The TPS56628EVM-534 output voltage ripple is shown in Figure 4-6. The output current is the rated full load of 6
A.
VOUT = 20 mV / div (ac coupled)
SW = 5 V / div
Time = 1 µsec / div
Figure 4-6. TPS56628EVM-534 Output Voltage Ripple (IOUT = 6 A)
The TPS56628EVM-534 output voltage ripple is shown in Figure 4-7. The output current is 500 mA.
VOUT = 20 mV / div (ac coupled)
SW = 5 V / div
Time = 1 µsec / div
Figure 4-7. TPS56628EVM-534 Output Voltage Ripple (IOUT = 500 mA)
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Test Setup and Results
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The TPS56628EVM-534 output voltage ripple is shown in Figure 4-8. The output current is 10 mA.
VOUT = 20 mV / div (ac coupled)
SW = 5 V / div
Time = 20 µsec / div
Figure 4-8. TPS56628EVM-534 Output Voltage Ripple (IOUT = 10 mA)
4.8 Input Voltage Ripple
The TPS56628EVM-534 input voltage ripple is shown in Figure 4-9. The output current is the rated full load of 6
A.
VIN = 100 mV / div (ac coupled)
SW = 5 V / div
Time = 1 µsec / div
Figure 4-9. TPS56628EVM-534 Input Voltage Ripple
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Test Setup and Results
4.9 Start-Up
The TPS56628EVM-534 start-up waveforms relative to VIN and EN are shown in Figure 4-10 and Figure 4-11.
RLOAD = 2 Ω.
VIN = 10 V / div
EN = 10 V / div
VOUT = 1 V / div
PG = 5 V / div
Time = 2 msec / div
Figure 4-10. TPS56628EVM-534 Start-Up Relative to VIN With VREG5, PG and VOUT
VIN = 10 V / div
EN = 10 V / div
VOUT = 1 V / div
PG = 5 V / div
Time = 2 msec / div
Figure 4-11. TPS56628EVM-534 Start-Up Relative to EN With VREG5, PG and VOUT
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Test Setup and Results
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4.10 Shut-Down
The TPS56628EVM-534 shut-down waveforms relative to VIN and EN are shown in Figure 4-12 and Figure 4-13.
RLOAD = 2 Ω.
VIN = 10 V / div
EN = 10 V / div
VOUT = 1 V / div
PG = 5 V / div
Time = 2 msec / div
Figure 4-12. TPS56628EVM-534 Shut-Down Relative to VIN With VREG5, PG and VOUT
VIN = 10 V / div
EN = 10 V / div
VOUT = 1 V / div
PG = 5 V / div
Time = 2 msec / div
Figure 4-13. TPS56628EVM-534 Shut-Down Relative to EN With VREG5, PG and VOUT
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Board Layout
5 Board Layout
This section provides a description of the TPS56628EVM-534, board layout, and layer illustrations.
5.1 Layout
The board layout for the TPS56628EVM-534 is shown in Figure 5-1 through Figure 5-5. The top layer contains
the main power traces for VIN, VOUT, and ground. Also on the top layer are connections for the pins of the
TPS56628 and a large area filled with ground. Many of the signal traces also are located on the top side. The
input decoupling capacitors are located as close to the IC as possible. The input and output connectors, test
points, and all of the components are located on the top side. Internal layer 1, internal layer 2 and the bottom
layer are predominantly power ground planes. An analog ground (AGND) area is provided on internal layer 1.
Analog ground (AGND) and power ground (PGND) are connected at a single point on internal layer 1 as shown.
Internal layer 2 contains an additional VIN area as well as a connection to the VIN pin of the EN control jumper
JP1. The bottom layer contains the output voltage feedback trace.
Figure 5-1. Top Assembly
Figure 5-2. Top Layer
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Board Layout
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Figure 5-3. Internal Layer 1
Figure 5-4. Internal Layer 2
Figure 5-5. Bottom Layer
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Schematic, Bill of Materials, and Reference
6 Schematic, Bill of Materials, and Reference
6.1 Schematic
Figure 6-1 is the schematic for the TPS56628EVM-534.
TP1
J1
VIN = 4.5 - 18 V
1
2
JP1
TP2
ON
EN
OFF
3
2
1
C1
C2
C3
10µF
10µF
0.1µF
R4
10.0k
PGND
TP3
PGND
1
R3
0
U1
TPS56628
AGND
R1
EN
2
VIN
VFB
VBST
8
TP5
7
8.25k
C7
VREG5
TP4
R5
open
4
PG
SW
6
TP8
L1
0.1µF
3
C4
PWR PAD
VIN
GND
1
VOUT = 1.05 V, IOUT = 6 A
2
1.5µH
PGND
5
C8
open
C10
C11
22µF
22µF
open
VOUT
GND
TP9
9
100k
C9
J2
1
2
R2
22.1k
AGND
C5
1µF
PGND
R6
C6
TP6
open
PGND
AGND
TP7
NT1
open
PGND
Net-Tie
PGND
AGND
PGND
PGND
Figure 6-1. TPS56628EVM-534 Schematic Diagram
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Schematic, Bill of Materials, and Reference
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6.2 Bill of Materials
Table 6-1. Bill of Materials
Designator
Qty
PCB
1
C1, C2
2
C3, C7
2
C4, C6, C8
0
C5
1
C9, C10
2
C11
Value
Description
Package Reference
Part Number
Manufacturer
Printed Circuit Board
2.00" x 2.50"
PWR534A
Any
10uF
CAP, CERM, 10uF, 35V, +10/%, X7R, 1210
1210
GRM32ER7YA106KA12L
MuRata
0.1uF
CAP, CERM, 0.1uF, 50V, +10/%, X7R, 0603
0603
GRM188R71H104KA93D
MuRata
CAP, CERM, xxxF, xxV, [TempCo], xx%, 0603
0603
1uF
CAP, CERM, 1uF, 25V, +10/%, X5R, 0603
0603
GRM188R61E105KA12D
MuRata
22uF
CAP, CERM, 22uF, 10V, +10/%, X5R, 1206
1206
GRM31CR61A226KE19L
MuRata
0
CAP, CERM, xxxF, xxV, [TempCo], xx%, 1206
1206
FID1, FID2,
FID3
0
Fiducial mark. There is nothing to buy or mount.
Fiducial
N/A
N/A
J1, J2
2
2x1
Conn Term Block, 2POS, 3.81mm, TH
PhoenixConact_1727010
1727010
Phoenix Contact
JP1
1
1x3
Header, TH, 100mil, 1x3, Gold plated, 230 mil above
insulator
PBC03SAAN
PBC03SAAN
Sullins Connector Solutions
L1
1
1.5µH
Inductor, SMT, 11A, 9.7 milliohm
0.256 x 0.280 inch
SPM6530-1R5M100
TDK
LBL1
1
Thermal Transfer Printable Labels, 1.25" W x 0.25" H 10,000 per roll
PCB Label 1.25"H x 0.25"W
THT-13-457-10
Brady
R1
1
8.25k
RES, 8.25k ohm, 1%, 0.1W, 0603
0603
CRCW06038K25FKEA
Vishay-Dale
R2
1
22.1k
RES, 22.1k ohm, 1%, 0.1W, 0603
0603
CRCW060322K1FKEA
Vishay-Dal
R3
1
0
RES, 0 ohm, 5%, 0.1W, 0603
0603
MCR03EZPJ000
Rohm
R4
1
10.0k
RES, 10.0k ohm, 1%, 0.1W, 0603
0603
CRCW060310K0FKEA
Vishay-Dale
R5
1
100k
RES, 100k ohm, 1%, 0.1W, 0603
0603
CRCW0603100KFKEA
Vishay-Dale
R6
0
RES, xxx ohm, x%, xW, 0603
0603
SH-JP1
1
1x2
Shunt, 100mil, Gold plated, Black
Shunt
969102-0000-DA
3M
TP1, TP5,
TP8
3
Red
Test Point, TH, Multipurpose, Red
Keystone5010
5010
Keystone
TP2, TP6,
TP7, TP9
4
Black
Test Point, TH, Multipurpose, Black
Keystone5011
5011
Keystone
TP3, TP4
2
White
Test Point, TH, Multipurpose, White
Keystone5012
5012
Keystone
U1
1
DC-DC Converter, 4.5 - 18 Vin, 6A
SOP8
TPS56628DDA
Texas Instruments
6.3 Reference
1. TPS56628, 4.5-V to 18-V Input, 6-A Synchronous Step-Down SWIFT™ Converter datasheet (SLVSC94)
7 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision * (October 2013) to Revision A (June 2021)
Page
• Updated user's guide title................................................................................................................................... 2
• Updated the numbering format for tables, figures, and cross-references throughout the document. ................2
16
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