Texas Instruments TPS53355EVM-864 User manual

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User's Guide
SLUUBJ6–November 2016
Green TPS53355EVM-864 Evaluation Module
The TPS53355EVM-864 evaluation module (EVM) allows users to evaluate the TPS53355. The
TPS53355 is a D-CAP™ mode, 30-A synchronous buck converter with integrated MOSFETs. It provides a
fixed 1.5-V output at up to 30 A from a 12-V input bus.
Contents
1 Introduction ................................................................................................................... 3
1.1 Before You Begin................................................................................................... 3
2 Description.................................................................................................................... 4
2.1 Typical Applications ................................................................................................ 4
2.2 Features.............................................................................................................. 4
3 Electrical Performance Specifications..................................................................................... 4
4 Schematic..................................................................................................................... 5
5 Test Setup .................................................................................................................... 6
5.1 Test Equipment ..................................................................................................... 6
5.2 Recommended Test Setup........................................................................................ 7
6 Configurations................................................................................................................ 8
6.1 Switching Frequency Selection ................................................................................... 8
6.2 Soft-Start Selection................................................................................................. 8
6.3 Mode Selection...................................................................................................... 8
6.4 Enable Selection ................................................................................................... 9
7 Test Procedure............................................................................................................... 9
7.1 Line/Load Regulation and Efficiency Measurement Procedure .............................................. 9
7.2 Control Loop Gain and Phase Measurement Procedure...................................................... 9
7.3 Test Point List...................................................................................................... 10
7.4 Equipment Shutdown............................................................................................. 10
8 Performance Data and Typical Characteristic Curves................................................................. 11
8.1 Efficiency ........................................................................................................... 11
8.2 Load Regulation................................................................................................... 11
8.3 Line Regulation.................................................................................................... 12
8.4 Enable Turnon/Turnoff............................................................................................ 12
8.5 Output Ripple ..................................................................................................... 13
8.6 Switching Node.................................................................................................... 13
8.7 Output Transient With Auto-Skip Mode ........................................................................ 14
8.8 Output Transient With FCCM Mode ............................................................................ 14
8.9 Output 0.75-V Prebias Turnon................................................................................... 15
8.10 Output Overcurrent and Short-Circuit Protection.............................................................. 15
8.11 Bode Plot........................................................................................................... 16
8.12 Thermal Image..................................................................................................... 17
9 EVM Assembly Drawing and PCB Layout .............................................................................. 18
10 Bill of Materials ............................................................................................................. 22
List of Figures
1 TPS53355EVM-864 Schematic............................................................................................ 5
2 Tip and Barrel Measurement for VOUT Ripple .......................................................................... 6
3 TPS53355EVM-864 Recommended Test Setup ........................................................................ 7
4 Efficiency .................................................................................................................... 11

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5 Load Regulation............................................................................................................ 11
6 Line Regulation............................................................................................................. 12
7 Enable Turnon.............................................................................................................. 12
8 Enable Turnoff.............................................................................................................. 12
9 Output Ripple ............................................................................................................... 13
10 Switching Node............................................................................................................. 13
11 Output Transient From DCM to CCM ................................................................................... 14
12 Output Transient From CCM to DCM ................................................................................... 14
13 Output Transient With FCCM Mode ..................................................................................... 14
14 Output 0.75-V Prebias Turnon ........................................................................................... 15
15 Output Overcurrent Protection............................................................................................ 15
16 Output Short Circuit........................................................................................................ 16
17 Bode Plot, VIN = 12 V, VOUT = 1.5 V, IOUT = 6 A, Frequency = 500 kHz.............................................. 16
18 Top Board at 12 VIN, 1.5 V/30 A, 25°C Ambient Temperature Without Airflow .................................... 17
19 TPS53355EVM-864 Top Layer Assembly Drawing ................................................................... 18
20 TPS53355EVM-864 Bottom Assembly Drawing ....................................................................... 18
21 TPS53355EVM-864 Top Copper ........................................................................................ 19
22 TPS53355EVM-864 Layer-2 Copper ................................................................................... 19
23 TPS53355EVM-864 Layer-3 Copper ................................................................................... 20
24 TPS53355EVM-864 Layer-4 Copper ................................................................................... 20
25 TPS53355EVM-864 Layer-5 Copper ................................................................................... 21
26 TPS53355EVM-864 Bottom Layer Copper ............................................................................ 21
List of Tables
1 TPS53355EVM-864 Electrical Performance Specifications............................................................ 4
2 Switching Frequency Selection ............................................................................................ 8
3 Soft-Start Time Selection................................................................................................... 8
4 MODE Selection ............................................................................................................. 8
5 Enable Selection............................................................................................................. 9
6 Test Point Functions....................................................................................................... 10
7 EVM Components List (see Schematic Figure 1)...................................................................... 22
Trademarks
D-CAP is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.

!
www.ti.com Introduction
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1 Introduction
1.1 Before You Begin
The following warnings and cautions are noted for the safety of anyone using or working close to the
TPS53355VQPEVM-864. Observe all safety precautions.
Warning The TPS53355VQPEVM-864 circuit module may become hot
during operation due to dissipation of heat. Avoid contact with
the board. Follow all applicable safety procedures applicable
to your laboratory.
Caution Do not leave the EVM powered when unattended.
WARNING
The circuit module has signal traces, components, and component
leads on the bottom of the board. This may result in exposed
voltages, hot surfaces or sharp edges. Do not reach under the
board during operation.
CAUTION
The circuit module may be damaged by over temperature. To avoid damage,
monitor the temperature during evaluation and provide cooling, as needed, for
your system environment.
CAUTION
Some power supplies can be damaged by application of external voltages. If
using more than 1 power supply, check your equipment requirements and use
blocking diodes or other isolation techniques, as needed, to prevent damage to
your equipment.
CAUTION
The communication interface is not isolated on the EVM. Be sure no ground
potential exists between the computer and the EVM. Also be aware that the
computer is referenced to the Battery- potential of the EVM.

Description www.ti.com
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2 Description
The TPS53355EVM-864 is designed to use a regulated 12-V bus to produce a regulated 1.5-V output at
up to 30 A of load current. The TPS53355EVM-864 is designed to demonstrate the TPS53355 in a typical,
low-voltage application while providing a number of test points to evaluate the performance of the
TPS53355.
2.1 Typical Applications
• Server/storage
• Workstations and desktops
• Telecommunication infrastructure
2.2 Features
The TPS53355EVM-864 features:
• 30-Adc, steady-state output current
• Supports prebias output voltage start-up
• J5 for selectable switching frequency setting
• J4 for selectable soft-start time
• J2 for enable function
• J6 for auto-skip and forced CCM selection
• Convenient test points for probing critical waveforms
3 Electrical Performance Specifications
Table 1. TPS53355EVM-864 Electrical Performance Specifications
Parameters Test Conditions Min Typ Max Units
Input Characteristics
Voltage range VIN 8 12 14 V
Maximum input current VIN = 8 V, IO= 30 A 6.3 A
No load input current VIN = 14 V, IO= 0 A with auto-skip mode 1 mA
Output Characteristics
Output voltage VOUT 1.5 V
Output voltage regulation Line regulation (VIN = 8 V – 14 V) 0.1 %
Load regulation (VIN = 12 V, IO= 0 A – 30 A) 1 %
Output voltage ripple VIN = 12 V, IO= 30 A 20 mVpp
Output load current 0 30 A
Output overcurrent 34 A
Systems Characteristics
Switching frequency 500 kHz
Peak efficiency VIN = 12 V, 1.5 V/10 A 91.87 %
Ful-load efficiency VIN = 12 V, 1.5V/30 A 89.46 %
Operating temperature 25 °C
NOTE: Jumpers are set to default locations; see Section 6 of this user’s guide

AUTOSKIP
2.8ms SS 1.4ms SS
5.6ms SS
0.7ms SS
+
+
+
250 kHz
300 kHz
400 kHz
500 kHz
650 kHz
750 kHz
850 kHz
970 kHz
FCCM
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4 Schematic
Figure 1 illustrates the EVM schematic.
Figure 1. TPS53355EVM-864 Schematic

TP7TP5
Metal Ground Barrel
Probe Tip
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5 Test Setup
5.1 Test Equipment
Voltage Source: The input voltage source VIN must be a 0-V to 14-V variable dc source capable of
supplying 10 Adc. Connect VIN to J1 as shown in Figure 3.
Multimeters:
• V1: VIN at TP1 (VIN) and TP2 (GND).
• V2: VOUT at TP5 (VOUT) and TP7 (GND).
• A1: VIN input current
Output Load: The output load must be an electronic constant resistance mode load capable of 0 Adc to
30 Adc at 1.5 V.
Oscilloscope: A digital or analog oscilloscope can be used to measure the output ripple. The oscilloscope
must be set for 1-MΩimpedance, 20-MHz bandwidth, ac coupling, 2-µs/division horizontal resolution, 50-
mV/division vertical resolution. Test points TP5 and TP7 can be used to measure the output ripple voltage
by placing the oscilloscope probe tip through TP5 and holding the ground barrel on TP7 as shown in
Figure 2. Using a leaded ground connection may induce additional noise due to the large ground loop.
Figure 2. Tip and Barrel Measurement for VOUT Ripple
Fan: Some of the components in this EVM may approach temperatures of 60°C during operation. A small
fan capable of 200–400 LFM is recommended to reduce component temperatures while the EVM is
operating. Only probe the EVM when the fan is running.
Recommended Wire Gauge:
1. VIN to J1 (12-V input):
The recommended wire size is 1x AWG 14 per input connection, with the total length of wire less than
4 feet (2-foot input, 2-foot return).
2. J3 to LOAD:
The minimum recommended wire size is 2x AWG 14, with the total length of wire less than 4 feet (2-
foot output, 2-foot return)

FAN
V1
A1
DC
Source
Vin
-
+
Load
+
V2
-
INSTRUMENTS
TEXAS
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5.2 Recommended Test Setup
Figure 3 is the recommended test setup to evaluate the TPS53355EVM-864. Working at an ESD
workstation, ensure that any wrist straps, bootstraps, or mats are connected referencing the user to earth
ground before power is applied to the EVM.
Figure 3. TPS53355EVM-864 Recommended Test Setup
Input Connections:
1. Prior to connecting the dc input source Vin, it is advisable to limit the source current from VIN to 10 A
maximum. Ensure that VIN is initially set to 0 V and connected as shown in Figure 3.
2. Connect a voltmeter V1 at TP1 (VIN) and TP2 (GND) to measure the input voltage.
3. Connect a current meter A1 to measure the input current.
Output Connections:
1. Connect Load to J3, and set Load to constant resistance mode to sink 0 Adc before VIN is applied.
2. Connect a voltmeter V2 at TP5 (VOUT) and TP7 (GND) to measure the output voltage.
Other Connections:
Place a fan as shown in Figure 3, and turn it on, making sure that air is flowing across the EVM.

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6 Configurations
All jumper selections must be made prior to applying power to the EVM. Users can configure this EVM per
the following configurations.
6.1 Switching Frequency Selection
The switching frequency can be set by J5.
Default setting: 500 kHz
Table 2. Switching Frequency Selection
Jumper Set to Resistor (RF) Connections
(kΩ)Switching Frequency (kHz)
Top (1–2 pin shorted) 0 250
Second (3–4 pin shorted) 187 300
Third (5–6 pin shorted) 619 400
Fourth (7–8 pin shorted) Open 500
Fifth (9–10 pin shorted) 866 650
Sixth (11–12 pin shorted) 309 750
Seventh (13–14 pin shorted) 124 850
Bottom (15–16 pin shorted) 0 970
6.2 Soft-Start Selection
The soft-start time can be set by J4.
Default setting: 1.4 ms
Table 3. Soft-Start Time Selection
Jumper Set to RMODE Connections (kΩ) Soft-Start Time (ms)
Top (1–2 pin shorted) 39.2 0.7
Second (3–4 pin shorted) 100 1.4
Third (5–6 pin shorted) 200 2.8
Bottom (7–8 pin shorted) 475 5.6
6.3 Mode Selection
The MODE can be set by J6.
Default setting: Auto Skip
Table 4. MODE Selection
Jumper Set to MODE Selection
Top (1–2 pin shorted) Auto Skip
Bottom (7–8 pin shorted) Forced CCM

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6.4 Enable Selection
The controller can be enabled and disabled by J2.
Default setting: Jumper shorts on J2 to disable the controller
Table 5. Enable Selection
Jumper Set to Enable Selection
Jumper shorts on J2 Disable the controller
No jumper shorts on J2 Enable the controller
7 Test Procedure
7.1 Line/Load Regulation and Efficiency Measurement Procedure
1. Set up EVM as described in Section 5 and Figure 3.
2. Ensure Load is set to constant resistance mode and to sink 0 Adc.
3. Ensure that all jumpers configuration settings are per Section 6.
4. Ensure that the jumper provided in the EVM shorts on J2 before Vin is applied.
5. Increase VIN from 0 V to 12 V. Use V1 to measure input voltage.
6. Remove the jumper on J2 to enable the controller.
7. Use V2 to measure VOUT voltage
8. Vary Load from 0 Adc to 30 Adc; Vout must remain in load regulation.
9. Vary VIN from 8 V to 14 V; Vout must remain in line regulation.
10. Put the jumper on J2 to disable the controller.
11. Decrease Load to 0 A
12. Decrease VIN to 0 V.
7.2 Control Loop Gain and Phase Measurement Procedure
TPS53355EVM-864 contains a 10-Ωseries resistor in the feedback loop for loop response analysis.
1. Set up the EVM as described in Section 5 and Figure 3.
2. Connect isolation transformer to test points marked TP10 and TP11.
3. Connect input signal amplitude measurement probe (channel A) to TP10. Connect output signal
amplitude measurement probe (channel B) to TP11.
4. Connect ground lead of channel A and channel B to TP12.
5. Inject an approximate 40-mV or less signal through the isolation transformer.
6. Sweep the frequency from 100 Hz to 1 MHz with 10-Hz or lower post filter. The control loop gain and
phase margin can be measured.
7. Disconnect isolation transformer from bode-plot test points before making other measurements. (Signal
injection into feedback may interfere with accuracy of other measurements.)

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7.3 Test Point List
Table 6. Test Point Functions
Test Points Name Description
TP1 VIN Controller input
TP2 GND Ground
TP3 GND Ground
TP4 EN Enable
TP5 VOUT Output voltage
TP6 LL Switching node
TP7 GND Ground
TP8 PGOOD Power Good
TP9 VREG 5-V LDO output
TP10 CHA Input A for loop injection
TP11 CHB Input B for loop injection
TP12 GND GND
7.4 Equipment Shutdown
1. Shut down Load.
2. Shut down fan.

12 Vin auto skip
14 Vin auto skip
8 Vin auto skip
12 Vin FCCM
14 Vin FCCM
8 Vin FCCM
0 5 10 15 20 25 30
I - Output Current - A
O
1.47
1.48
1.49
1.5
1.51
1.52
1.53
V - Output Voltage - V
O
0.001 0.01 0.1 1 10 100
I - Output Current - A
O
12 Vin auto skip
14 Vin auto skip
8 Vin auto skip
12 Vin FCCM
14 Vin FCCM
8 Vin FCCM
0
10
20
30
40
50
60
70
80
90
100
Efficiency - %
www.ti.com Performance Data and Typical Characteristic Curves
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8 Performance Data and Typical Characteristic Curves
Figure 4 through Figure 18 present typical performance curves for TPS53355EVM-864.
8.1 Efficiency
Figure 4. Efficiency
8.2 Load Regulation
Figure 5. Load Regulation

Test condition: 12 Vin, 1.5 V/30 A
Auto Skip Mode
TPS5335EVM
Enable Shut Down
CH1: EN
CH2: 1.5 Vout
CH3: PGOOD
TPS5335EVM
Enable Start Up
Test condition: 12 Vin, 1.5 V/30 A
Auto Skip Mode
CH1: EN
CH2: 1.5 Vout
CH3: PGOOD
1.47
1.48
1.49
1.5
1.51
1.52
1.53
8 9 10 11 12 13 14
V - Input Voltage - V
I
I = 0 A auto-skip
O
V - Output Voltage - V
O
I = 0 A FCCM
O
I = 30 A
O
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8.3 Line Regulation
Figure 6. Line Regulation
8.4 Enable Turnon/Turnoff
Figure 7. Enable Turnon Figure 8. Enable Turnoff

Test condition: 12 Vin, 1.5 V/30 A
Auto Skip Mode
TPS5335EVM
Switching Node
CH1: LL
Test condition: 12 Vin, 1.5 V/30 A
Auto Skip Mode
TPS5335EVM
Output Ripple
CH1: 1.5 Vout
V1: 2.4 mV
V2: -9.6 mV
V: -12.0 mVD
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8.5 Output Ripple
Figure 9. Output Ripple
8.6 Switching Node
Figure 10. Switching Node

Test condition: 12 Vin, 1.5 V/0 A-15 A
FCCM Mode
TPS5335EVM
Output Transient from 0 A to 15 A
CH1: 1.5 Vout
CH4: output Current
Test condition: 12 Vin, 1.5 V/15 A-0 A
Auto Skip Mode
TPS5335EVM
Output Transient from CCM to DCM
CH1: 1.5 Vout
CH4: Output Current
Test condition: 12 Vin, 0 A -
Auto Skip Mode
15 A
TPS5335EVM
Output Transient from DCM to CCM
CH1: 1.5 Vout
CH4: Output Current
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8.7 Output Transient With Auto-Skip Mode
Figure 11. Output Transient From DCM to CCM Figure 12. Output Transient From CCM to DCM
8.8 Output Transient With FCCM Mode
Figure 13. Output Transient With FCCM Mode

TPS53355EVM
Over Current Protection
Test Condition: 12 Vin OCP
Ch1: 1.5 Vout
Ch2: LL
Ch3: PGOOD
Test condition: 12 Vin, 1.5 V/0 A
FCCM Mode
TPS5335EVM
0.75 V Pre-bias Enable Start up
CH1: EN
CH2: 1.5 Vout
CH3: PGOOD
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8.9 Output 0.75-V Prebias Turnon
Figure 14. Output 0.75-V Prebias Turnon
8.10 Output Overcurrent and Short-Circuit Protection
Figure 15. Output Overcurrent Protection

TPS53355EVM
Short Circuit Protection
Ch1: 1.5 Vout
Ch2: LL
Ch3: PGOOD
Test Condition: 12 Vin,
1.5 V Short Circuit
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Figure 16. Output Short Circuit
8.11 Bode Plot
Figure 17. Bode Plot, VIN = 12 V, VOUT = 1.5 V, IOUT = 6 A, Frequency = 500 kHz

www.ti.com Performance Data and Typical Characteristic Curves
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8.12 Thermal Image
Figure 18 shows a thermal image of the board.
Figure 18. Top Board at 12 VIN, 1.5 V/30 A, 25°C Ambient Temperature Without Airflow

INSTRUMENTS
TEXAS
EVM Assembly Drawing and PCB Layout www.ti.com
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9 EVM Assembly Drawing and PCB Layout
The following illustrations (Figure 19 through Figure 26) show the design of the TPS53355EVM-864
printed-circuit board. The EVM was designed using a 6-layer, 2-oz copper circuit board.
Figure 19. TPS53355EVM-864 Top Layer Assembly Drawing
Figure 20. TPS53355EVM-864 Bottom Assembly Drawing

www.ti.com EVM Assembly Drawing and PCB Layout
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Figure 21. TPS53355EVM-864 Top Copper
Figure 22. TPS53355EVM-864 Layer-2 Copper

EVM Assembly Drawing and PCB Layout www.ti.com
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Figure 23. TPS53355EVM-864 Layer-3 Copper
Figure 24. TPS53355EVM-864 Layer-4 Copper