Texas Instruments TPS40345EVM-353 User manual

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TPS40345EVM-353 Evaluation Module
User's Guide
SNVU588–November 2017
TPS40345EVM-353 Evaluation Module
The TPS40345EVM-353 evaluation module (EVM) is a synchronous buck converter providing a fixed
1.2-V output at up to 20 A from a 12-V input bus. The EVM is designed to start-up from a single supply,
which means no additional bias voltage is required for start-up. The module uses the TPS40345 high-
performance, mid-input voltage synchronous buck controller and TI’s NexFET™ high performance
MOSFETs.
Contents
1 Description.................................................................................................................... 3
1.1 Applications.......................................................................................................... 3
1.2 Features.............................................................................................................. 3
2 TPS40345EVM-353 Electrical Performance Specifications............................................................ 3
3 TPS40345EVM-353 Schematic............................................................................................ 4
4 Connector and Test Point Descriptions................................................................................... 5
4.1 Enable Jumper (JP2)............................................................................................... 5
4.2 Frequency Spread Spectrum – FSS Jumper (JP1) ............................................................ 5
4.3 Test Point Descriptions ............................................................................................ 5
5 Test Setup .................................................................................................................... 7
5.1 Equipment ........................................................................................................... 7
5.2 Equipment Setup.................................................................................................... 7
5.3 Start-Up/Shutdown Procedure .................................................................................... 9
5.4 Output Ripple Voltage Measurement Procedure ............................................................... 9
5.5 Control Loop Gain and Phase Measurement Procedure...................................................... 9
5.6 Equipment Shutdown............................................................................................. 10
6 TPS40345EVM-353 Test Data ........................................................................................... 10
6.1 Efficiency ........................................................................................................... 10
6.2 Line and Load Regulation........................................................................................ 11
6.3 Output Voltage Ripple ............................................................................................ 11
6.4 Switch Node........................................................................................................ 12
6.5 Control Loop Bode Diagram ..................................................................................... 12
6.6 Additional Waveforms ............................................................................................ 13
7 TPS40345EVM-353 Assembly Drawings and Layout................................................................. 13
8 TPS40345EVM-353 Bill of Materials..................................................................................... 17
List of Figures
1 TPS40345EVM-353 Schematic............................................................................................ 4
2 TPS40345EVM-353 Recommended Test Set-Up....................................................................... 8
3 Output Ripple Measurement – Tip and Barrel using TP3 and TP4................................................... 8
4 Control Loop Measurement Setup......................................................................................... 9
5 TPS40345EVM-353 Efficiency vs Load Current ....................................................................... 10
6 TPS40345EVM-353 Output Voltage vs Load Current................................................................. 11
7 TPS40345EVM-353 Output Voltage Ripple ............................................................................ 11
8 TPS40345EVM-353 Switching Waveforms............................................................................. 12
9 TPS40345EVM-353 Gain and Phase vs Frequency .................................................................. 12
10 TPS40345EVM-353 Output Ripple With FSS Enabled ............................................................... 13
11 TPS40345EVM-353 Component Placement (Top View) ............................................................. 14

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12 TPS40345EVM-353 Silk Screen (Top View) ........................................................................... 14
13 TPS40345EVM-353 Top Copper (Top View)........................................................................... 15
14 TPS40345EVM-353 Bottom Copper (Top View)....................................................................... 15
15 TPS40345EVM-353 Internal 1 (X-Ray Top View) ..................................................................... 16
16 TPS40345EVM-353 Internal 2 (X-Ray Top View) ..................................................................... 16
List of Tables
1 TPS40345EVM-353 Electrical and Performance Specifications ...................................................... 3
2 Test Point Descriptions ..................................................................................................... 5
3 TPS40345EVM-353 Bill of Materials..................................................................................... 17
Trademarks
NexFET is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.

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TPS40345EVM-353 Evaluation Module
1 Description
The TPS40345EVM-353 is designed to use a regulated 12 V (8 V – 14 V) bus voltage to provide a
regulated 1.2-V output at up to 20 A of load current. The TPS40345EVM-353 is designed to demonstrate
the TPS40345 controller and TI NexFETs in a typical 12-V bus to low-voltage application while providing a
number of non-invasive test points to evaluate the performance of the TPS40345 and TI NexFETs in a
given application.
1.1 Applications
• High-current, low-voltage FPGA or microcontroller core supplies
• High-current point of load modules
• Telecommunications equipment
• Computer peripherals
1.2 Features
• 8-V to 14-V input voltage rating
• 1.2-V ± 2% output voltage rating
• 20-A steady state load current
• 600-kHz switching frequency
• Simple access to IC features including power good, enable, soft start, and error amplifier
• Convenient test points for simple, non-invasive measurements of converter performance
2 TPS40345EVM-353 Electrical Performance Specifications
Table 1. TPS40345EVM-353 Electrical and Performance Specifications
PARAMETER NOTES AND CONDITIONS MIN TYP MAX UNIT
INPUTS CHARACTERISTICS
VIN Input voltage 8 12 14 V
IIN Input current VIN = Nom, IOUT = Max 2.3 2.5 A
No load input current VIN = Nom, IOUT = 0A 40 50 mA
VIN_UVLO Input UVLO IOUT = 10 A 3.0 V
OUTPUTS CHARACTERISTICS
VOUT1 Output voltage 1 VIN = 12 V, IOUT = 20 A 1.17 1.2 1.23 V
Line regulation VIN = 8 V to 14 V 0.5%
Load regulation IOUT = 0 A to 20 A 0.5%
VOUT_ripple Output voltage ripple VIN = 12 V, IOUT = 20 A 24 mVpp
IOUT1 Output current 1 VIN = 8 V to 14 V 0 20 A
SYSTEMS CHARACTERISTICS
fSW Switching frequency 540 600 660 kHz
ηpk Peak efficiency VIN = 12 V 88%
ηFull load efficiency VIN = 12 V, IOUT = 20 A 86%

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TPS40345EVM-353 Schematic www.ti.com
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3 TPS40345EVM-353 Schematic
For reference only, See Table 3 for specific values
Figure 1. TPS40345EVM-353 Schematic

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4 Connector and Test Point Descriptions
4.1 Enable Jumper (JP2)
The TPS40345EVM-353 is designed with a Disable Jumper (JP2) using a 0.1-inch spacing header and
shunt. Installing a shunt in the JP2 position connects the EN/SS pin to GND, discharges the soft-start
capacitor, and disables the TPS40304 controller. This forces the output into a high-impedance state
(approximately 20kΩto GND).
4.2 Frequency Spread Spectrum – FSS Jumper (JP1)
The TPS40345EVM-353 is designed with a frequency spread spectrum (FSS) enable jumper (JP1) using
a 0.1" spacing header and shunt. Installing a shunt in the JP1 position connects the EN/SS pin to BP via a
267-kΩresistor (R10) to enable frequency spread spectrum.
FSS modulates the switching frequency to ±10% of the nominal value at 30 kHz to reduce EMI at the
switching frequency and its harmonics, however there may be a 30-kHz component to the output ripple
(see Figure 10).
The TPS40345EVM-353 does not dynamically monitor the JP1 status for programming FSS. The
TPS40345EVM-353 must be disabled via JP2 or powered down by reducing VIN to less than 3 V to
remove or install JP1.
4.3 Test Point Descriptions
Table 2. Test Point Descriptions
TEST
POINT LABEL USE SECTION
TP1 VIN Measurement test point for input voltage 4.3.1
TP2 GND Ground test point for input voltage 4.3.1
TP3 VOUT Measurement test point for output voltage 4.3.1
TP4 GND Ground test point for output voltage 4.3.2
TP5 CHB Measurement test point for channel B of loop response 4.3.3
TP6 SGND Ground test point for channel B of loop response 4.3.3
TP7 CHA Measurement test point for channel A of loop response 4.3.3
TP8 SGND Ground test point for channel A of loop response 4.3.3
TP9 SGND Ground test point for error amplifier measurements 4.3.4
TP10 COMP Measurement test point for error amplifier output voltage 4.3.4
TP11 FB Measurement test point for error amplifier input voltage 4.3.4
TP12 HDRV Measurement test point for high-side gate driver voltage 4.3.5
TP13 SW Measurement test point for switching node voltage 4.3.5
TP14 LDRV Measurement test point for low-side gate driver voltage 4.3.5
TP15 PGND Ground test point for switch node and gate drive voltages 4.3.5
TP16 PGOOD Measurement test point for power good 4.3.6
TP17 EN/SS Measurement test point for enable / soft start 4.3.7
TP18 SGND Ground test point for power good and enable / soft start 4.3.6 and 4.3.7

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4.3.1 Input Voltage Monitoring (TP1 and TP2)
The TPS40345EVM-353 provides two test points for measuring the input voltage applied to the module.
This allows the user to measure the actual input module voltage without losses from input cables and
connectors. All input voltage measurements should be made between TP1 and TP2. To use TP1 and
TP2, connect a voltmeter positive input to TP1 and input terminal to TP2.
4.3.2 Output Voltage Monitoring (TP3 and TP4)
The TPS40345EVM-353 provides two test points for measuring the output voltage generated by the
module. This allows the user to measure the actual module output voltage without losses from input
cables and connectors. All input voltage measurements should be made between TP3 and TP4. To use
TP3 and TP4, connect a voltmeter positive input to TP3 and negative input to TP4.
4.3.3 Loop Response Testing (TP5, TP6, TP7, TP8, and R3)
The TPS40345EVM-353 provides four test points (2 signal and 2 ground) for measuring the control loop
frequency response. This allows the user to measure the actual module loop response without modifying
the evaluation board. A transformer isolated signal up to 30 mV can be injected between TP5 and TP7.
The injected signal amplitude can be measured by the ac coupled amplitude at CHA (TP7) and the
resulting output voltage deviation can be measured at CHB (TP5). See Figure 4 for additional detail.
4.3.4 Error Amplifier Voltage Monitoring (TP9, TP10, and TP11)
The TPS40345EVM-353 provides three test points for measuring the error amplifier input and output
voltages. This allows the user to directly measure the feedback and control voltages of the TPS40304
controller. The control voltage (TP10) can also be used to measure the control to output or power-stage
frequency response or output to control or error amplifier frequency response. See Section 5.5 for
additional details.
4.3.5 Switching Waveform Monitoring (TP12, TP13, TP14, and TP15)
The TPS40345EVM-353 provides three test points and a local power ground for measuring the switching
waveforms of the module power stage. This allows the user to monitor actual switching waveforms during
operation. TP13 is a 0.040-inch square pad of exposed PCB copper to minimize EMI radiation from the
high transient voltages on the switch node. Switching waveform measurements should be made using
power ground (TP15) as the ground reference for more accurate measurements.
4.3.6 Power-Good Voltage Monitoring (TP16 and TP18)
The TPS40345EVM-353 provides a test point and local ground for measuring the power good output
voltage. A 100-kΩresistor pullup to BP (R9) is included to allow the power-good signal to be monitored
without requiring an external pull-up. For true open-drain operation with no pullup, remove R9. With R9
removed, TP16 can be connected to TP17 of another TPS40345EVM-353 to provide sequential start-up of
the two TPS40345EVM-353 converters.
4.3.7 Enable and Soft-Start Voltage Monitoring (TP17 and TP18)
The TPS40345EVM-353 provides a test point and local ground for measuring the enable and soft-start
voltage. TP17 and TP18 or JP2 can be used to provide an external enable signal. Due to the nature of the
soft-start function, the external signal must be open-collector or open-drain without pullup.

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5 Test Setup
5.1 Equipment
5.1.1 Voltage Source
VIN — The input voltage source (VIN) must be a 0-V to 15-V variable DC source capable of supplying 5
Adc.
5.1.2 Meters
A1: — Input current meter. 0 Adc – 5 Adc ammeter
V1: — Input voltage meter. 0 V – 15 V voltmeter
V2: — Output voltage meter. 0 V – 2 V voltmeter
5.1.3 Load
LOAD1: — Output load. Electronic load set for constant current or constant resistance capable of 0 Adc –
20 Adc at 1.2-Vdc.
5.1.4 Oscilloscope
For output voltage ripple: — Oscilloscope must be an analog or digital oscilloscope set for ac-coupled
measurement with 20-MHz bandwidth limiting. Use 20 mV/division vertical resolution, 1-µs/division
horizontal resolution.
For switching waveforms: — Oscilloscope shall be an analog or digital oscilloscope set for dc coupled
measurement with 20-MHz bandwidth limiting. Use 2 V/division or 5V/division vertical resolution and 1-
µs/division horizontal resolution.
5.1.5 Recommended Wire Gauge
VIN to J1: — The connection between the source voltage (VIN) and J1 of TPS40345EVM-353 can carry as
much as 3.5 Adc of current. The minimum recommended wire size is AWG #16 with the total length of
wire less than 2 feet (1 foot input, 1 foot return).
J2 to LOAD1: — The connection between the source voltage (VIN) and J1 of TPS40345EVM-353 can
carry as much as 20 Adc of current. The minimum recommended wire size is AWG #12 with the total
length of wire less than 2 feet (1 foot input, 1 foot return).
5.1.6 Other
FAN: — The TPS40345EVM-353 evaluation module includes components that can get hot to the touch
when operating. Because this evaluation module is not enclosed to allow probing of circuit nodes, TI
recommends a small fan capable of 200 lfm – 400 lfm to reduce component temperatures when operating.
5.2 Equipment Setup
Shown in Figure 2 is the basic test set up recommended to evaluate the TPS40345EVM-353. Note that
although the return for J1 and JP2 are the same system ground, the connections should remain separate
as shown in Figure 2.
5.2.1 Procedure
1. Working at an ESD workstation, make sure that any wrist straps, bootstraps, or mats are connected
referencing the user to earth ground before power is applied to the EVM. Electrostatic smock and
safety glasses should also be worn.
2. Prior to connecting the dc input source, VIN, it is advisable to limit the source current from VIN to 4 A,
maximum. Make sure VIN is initially set to 0 V and connected as shown in Figure 2.
3. Connect VIN to J1 as shown in Figure 2.

TP4TP3
Metal Ground Barrel
Probe Tip
Tip and Barrel Vout ripple
measurement
LOAD1
1.2V @
20A
+
-
FAN
V2
-
+
See Tip and Barrel
Measurement for
Vout ripple
V1
+
-
A1
-
+
VIN
Oscilloscope
1MW, AC
20mV / div
20MHz
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4. Connect ammeter A1 between VIN and J1 as shown in Figure 2.
5. Connect voltmeter V1 to TP1 and TP2 as shown in Figure 2.
6. Connect voltmeter V2 to TP3 and TP4 as shown in Figure 2.
7. Connect oscilloscope probes to desired test points per Table 2.
8. Place fan as shown in Figure 2 and turn on making sure to blow air directly across the evaluation
module.
5.2.2 Diagram
Figure 2. TPS40345EVM-353 Recommended Test Set-Up
Figure 3. Output Ripple Measurement – Tip and Barrel using TP3 and TP4

Network
Analyzer
Isolation
Transformer
LOAD1
1.2V @
20A
+
-
V2
-
+
See Tip and Barrel
Measurement for
Vout ripple
V1
+
-
A1
-
+
VIN
Oscilloscope
1MW, AC
20mV / div
20MHz
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Figure 4. Control Loop Measurement Setup
5.3 Start-Up/Shutdown Procedure
1. Verify shunt position for JP1 for desired FSS status per _________(need correct reference).
2. Remove shunt from JP2 location if present.
3. Increase VIN from 0 Vdc to 12 Vdc.
4. Vary LOAD1 from 0 Adc to 20 Adc.
5. Vary VIN from 8 V to 14 V.
6. Decrease VIN to 0 V.
7. Decrease LOAD1 to 0 A.
5.4 Output Ripple Voltage Measurement Procedure
1. Follow Section 5.3 steps 1 – 5 to set VIN and LOAD1 to the desired operating condition.
2. Connect oscilloscope probe with exposed metal barrel to TP3 and TP4 per Figure 3.
3. Set oscilloscope per oscilloscope for output voltage ripple measurement in Section 5.1.4.
4. Follow Section 5.3 steps 6 and 7 to power down.
5.5 Control Loop Gain and Phase Measurement Procedure
1. Follow Section 5.3 steps 1 – 5 to set VIN and LOAD1 to the desired operating condition:
a. If JP1 is installed (FSS enabled), loop response data about the modulation frequency (30 kHz)
may be affected.
2. Connect a 1-kHz – 1-MHz isolation transformer to TP5 and TP7 as shown in Figure 4.

0 5 10 15 20
I - Load Current - A
L
8 V 12 V
14 V
60
65
70
75
80
85
90
95
h- Efficiency - %
Channel B
20 LOG
Channel A
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´ç ÷
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3. Connect input signal amplitude measurement probe (channel A) to TP7 as shown in Figure 4.
4. Connect output signal amplitude measurement probe (channel B) to TP5 as shown in Figure 4.
5. Connect ground lead of channel A and channel B to TP6 and TP8 as shown in Figure 4.
6. Inject 30 mV or less signal across R3 through isolation transformer.
7. Sweep frequency from 1 kHz to 1 MHz with 10-Hz or lower post filter.
8. Control loop gain can be measured by
9. Control loop phase can be measured by the phase difference between channel A and channel B.
10. Control to output response (power stage transfer function) can be measured by connecting channel A
probe to TP10 (COMP) and channel B probe to TP5 (CHB).
11. Output to control response (compensated error amplifier transfer function) can be measured by
connecting channel A probe to TP7 (CHA) and channel B probe to TP10 (COMP).
12. Follow Section 5.3 steps 6 and 7 to power down.
5.6 Equipment Shutdown
1. Shut down oscilloscope
2. Shut down LOAD1
3. Shut down VIN
4. Shut down fan
6 TPS40345EVM-353 Test Data
Figure 5 through Figure 10 present typical performance curves for the TPS40345EVM-353. Since actual
performance data can be affected by measurement techniques and environmental variables, these curves
are presented for reference and may differ from actual field measurements.
6.1 Efficiency
VIN = 8.0V – 14V, VOUT = 1.2V, IOUT = 0A – 20A
Figure 5. TPS40345EVM-353 Efficiency vs Load Current