Texas Instruments TPS40074EVM-001 User manual

User’s Guide
TPS40074 Buck Controller Evaluation Module User's
Guide
Table of Contents
1 Introduction.............................................................................................................................................................................2
1.1 Description......................................................................................................................................................................... 2
1.2 Applications........................................................................................................................................................................2
1.3 Features............................................................................................................................................................................. 2
2 TPS40074EVM-001 Electrical Performance Specifications................................................................................................ 2
3 Schematic ...............................................................................................................................................................................4
3.1 Adjusting Output Voltage (R5 and R6)............................................................................................................................... 5
3.2 Using Remote Sense (J3).................................................................................................................................................. 5
3.3 5V Input Operation (R10 and R15).................................................................................................................................... 5
4 Test Setup................................................................................................................................................................................6
4.1 Equipment.......................................................................................................................................................................... 6
4.2 Equipment Setup................................................................................................................................................................7
4.3 Start-Up/Shutdown Procedure........................................................................................................................................... 8
4.4 Equipment Shutdown......................................................................................................................................................... 8
5 TPS40074EVM Typical Performance Data and Characteristic Curves...............................................................................9
5.1 Efficiency............................................................................................................................................................................9
5.2 Line and Load Regulation.................................................................................................................................................. 9
6 EVM Assembly Drawings and Layout.................................................................................................................................10
7 List of Materials.....................................................................................................................................................................13
8 Revision History................................................................................................................................................................... 14
List of Figures
Figure 3-1. TPS40074EVM-001 Power Stage/Control Schematic Reference Only, See Table 3 for Specific Values................. 4
Figure 4-1. TPS40074EVM-001 Recommended Test Setup....................................................................................................... 7
Figure 4-2. Output Ripple Measurement – Tip and Barrel using TP15 and TP16....................................................................... 8
Figure 5-1. TPS40074EVM-001 Efficiency V12V_IN = 10 V–14 V, V1V5_OUT = 1.5 V, I1V5_OUT = 0 A–15 A...................................9
Figure 5-2. TPS40074EVM-001 Line and Load Regulation – ±1% Window............................................................................... 9
Figure 6-1. TPS40074EVM-001 Component Placement (Viewed from Top).............................................................................10
Figure 6-2. TPS40074EVM-001 Silkscreen (Viewed from Top).................................................................................................10
Figure 6-3. TPS40074EVM-001 Top Copper (Viewed from Top)............................................................................................... 11
Figure 6-4. TPS40074EVM-001 Layer 2 (X-Ray View from Top)...............................................................................................11
Figure 6-5. TPS40074EVM-001 Layer 3 (X-Ray View from Top).............................................................................................. 12
Figure 6-6. TPS40074EVM-001 Bottom Copper (X-Ray View from Top).................................................................................. 12
List of Tables
Table 2-1. TPS40074EVM-001 Electrical and Performance Specifications.................................................................................2
Table 3-1. Adjusting V1V5_OUT With R14...................................................................................................................................... 5
Table 7-1. TPS40074EVM-001 Bill of Materials.........................................................................................................................13
Trademarks
All trademarks are the property of their respective owners.
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TPS40074 Buck Controller Evaluation Module User's Guide 1
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1 Introduction
The TPS40074EVM-001 evaluation module (EVM) is a synchronous buck converter providing a fixed 1.5-V
output at up to 15 A from a 12-V input bus. The EVM is designed to start up from a single supply, so no
additional bias voltage is required for start-up. The module uses the TPS40074 high frequency controller with
remote sense.
1.1 Description
The TPS40074EVM-001 is designed to use a regulated 12-V (between 10-V and 14-V) bus to produce a high
current, regulated 1.5-V output at up to 15 A of load current. The TPS40074EVM-001 is design to demonstrate
the TPS40074 in a typical regulated bus to low-voltage application while providing a number of test points to
evaluate the performance of the TPS40074 in a given application. The EVM can be modified to support output
voltages from 0.9 V to 3.3 V by changing a single resistor. The TPS40074EVM-001 has been built to the sample
application used in the TPS40074 Midrange Input Synchronous Buck Controller With Voltage Feed-Forward
Data Sheet, except the switching frequency has been lowered to 400 kHz to reduce switching losses in the
power FETs, and the RKFF resistor (R10) increased to maintain the UVLO level.
1.2 Applications
• Non-isolated medium current point of load and low voltage bus converters
• Merchant power modules
• Networking equipment
• Telecommunications equipment
• DC power distributed systems
1.3 Features
• 10-V to 14-V input range
• 1.5-V fixed output, adjustable with single resistor
• 15-ADC steady state output current
• 400-kHz switching frequency
• Single main switch MOSFET and single synchronous rectifier MOSFET single
• Component side, surface mount design on a 3-inch × 3-inch evaluation board
• Four-layer PCB with all components on the top side
• Convenient test points for probing critical waveforms and non-invasive loop response testing
2 TPS40074EVM-001 Electrical Performance Specifications
Table 2-1. TPS40074EVM-001 Electrical and Performance Specifications
PARAMETER NOTES AND CONDITIONS MIN TYP MAX UNIT
INPUT CHARACTERISTICS
Input voltage range 10 14 V
Max input current VIN = 10 V, IOUT = 15 A 2.75 A
No-load input current VIN = 14 V, IOUT = 0 A 45 mA
OUTPUT CHARACTERISTICS
Output voltage R6 = 9.53 k, R5 = 105 k 1.45 1.50 1.55 V
Output voltage regulation Line regulation (10 V < VIN < 14 V, IOUT = 5 A) 1%
Load regulation (10 V < IOUT < 15 A, VIN = 12 V) 1%
Output voltage ripple VIN = 14 V, IOUT = 15 A 25 50 mVpp
Output load current 0 15 A
Output over current 23 A
SYSTEM CHARACTERISTICS
Switching frequency 360 400 440 kHz
Peak efficiency VOUT = 1.5 V, 8 A < IOUT < 12 A V12V_IN = 10 V 87%
V12V_IN = 12 V 85%
V12V_IN = 14 V 83%
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Table 2-1. TPS40074EVM-001 Electrical and Performance Specifications (continued)
PARAMETER NOTES AND CONDITIONS MIN TYP MAX UNIT
Full load efficiency VOUT = 1.5 V, IOUT = 15 A V12V_IN = 10 V 84%
V12V_IN = 12 V 83%
V12V_IN = 14 V 81%
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3 Schematic
+
+++
+
Figure 3-1. TPS40074EVM-001 Power Stage/Control Schematic Reference Only, See Table 3 for Specific
Values
Schematic www.ti.com
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3.1 Adjusting Output Voltage (R5 and R6)
The regulated output voltage can be adjusted within a limited range by changing the ground resistor in the
feedback resistor divider (R6 and R5). The output voltage is given by Equation 1.
VVOUT +VVREF R5 )R65 )R3
R5 )R6
(1)
where
• VVREF = 0.700 V
• R3 = 10.0 kΩ
Table 3-1 contains common values for R6 to generate popular output voltages with R5 open R5 can be used to
increase the accuracy that can be obtained without using more expensive resistors. The TPS40074EVM-001 is
stable through these output voltages but the efficiency can suffer as the power stage is optimized for the 1.5-V
output.
Table 3-1. Adjusting V1V5_OUT With R14
VOUT R16
3.3 V(1) 2.67 K
2.5 V(1) 3.83 K
2.2 V(1) 4.64 K
2.0 V(1) 8.36 K
1.8 V 6.34 K
1.5 V 8.66 K
1.2 V 14.0 K
(1) Due to higher duty cycles associated with higher output voltages or lower input voltages, output
current should be limited to 10 A when operating with output voltages greater than 2.0 V or input
voltages below 6 V to reduce conduction losses in the main switching FET (Q1). Under these
conditions, a lower RdsON FET would normally be selected.
3.2 Using Remote Sense (J3)
The TPS40074EVM-001 provides the user with remote sense capabilities through the connector J3. When
remote sense is used, J3 should be connected at the load to provide more accurate load regulation by
compensating for losses over the terminal connections and load wire connections. When remote sense
is connected the output voltage measured between TP15 and TP16 can show a positive load regulation
characteristic (increasing output voltage with increasing load). This is the result of the compensation of the
controller of resistive losses between the local sense voltage (TP15 and TP16) and the remote sense connection
(J3). TP17 and TP18 are connected to the remote sense lines and thus will show the voltage at the load when
remote sense is connected.
Excessive phase shift from inductive components in the load or remote sense connections can cause instability
if care is not taken to minimize these parasitic effects in the remote sense line. A twisted pair of insulated cables
from the load connection to J3 is preferred to minimize noise injection and inductance in the remote sense line.
In a device layout, care should be taken to shield the remote sense line from high-noise, high-current, or digital
signals to limit noise injection into the feedback path and provide the most accurate regulation possible.
3.3 5V Input Operation (R10 and R15)
To operate with a 5-V input, two resistors need to be changed. R10 (RKFF) sets the voltage ramp amplitude and
needs to be reduced to 53.6 kΩ to lower the UVLO to 3.9 V for 5-V operation. In addition, a 330-kΩ resistor
should be added at R15 to prevent an internal race condition during soft start.1
1Due to higher duty cycles associated with higher output voltages or lower input voltages, output current should be limited to 10 A when
operating with output voltages greater than 2.0 V or input voltages below 6 V to reduce conduction losses in the main switching FET
(Q1). Under these conditions, a lower RdsON FET would normally be selected.
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4 Test Setup
4.1 Equipment
4.1.1 Voltage Source
V12V_IN
The input voltage source (V12V_IN) should be a 0-V to 15-V variable DC source capable of 5 ADC. Connect
V12V_IN to J1 as shown in Figure 4-2.
4.1.2 Meters
A1: 0 ADC 5 ADC, ammeter
V1: V12V_IN, 0-Vto 15-V voltmeter
V2: V1V5_OUT 0-V to 5-V voltmeter
4.1.3 Loads
LOAD1
The output load (LOAD1) should be an electronic constant current mode load capable of 0 ADC–15 ADC at 1.5 V.
4.1.4 Recommended Wire Gauge
V12V_IN to J1
The connection between the source voltage, V12V_IN, and J1 of HPA095 can carry as much as 3 ADC. The
minimum recommended wire size is AWG #16 with the total length of wire less than four feet (2-feet input, 2-feet
return).
J2 to LOAD1 (Power)
The power connection between J2 of HPA095 and LOAD1 can carry as much as 15 ADC. The minimum
recommended wire size is 2× AWG #16, with the total length of wire less than four feet (2-feet output, 2-feet
return).
J3 to LOAD1 (Remote Sense)
If remote sense is used, the remote sense connection between J3 of HPA095 and LOAD1 can carry less than 1
ADC. The minimum recommended wire size is AWG #22, with the total length of wire less and four feet (2-feet
output, 2-feet return).
4.1.5 Other
FAN
This evaluation module includes components that can get hot to the touch, because this EVM is not enclosed
to allow probing of circuit nodes, a small fan capable of 200–400 lfm is required to reduce component surface
temperatures to prevent user injury. The EVM should not be left unattended while powered or probed while the
fan is not running.
OSCILLOSCOPE
A 60-MHz or faster oscilloscope can be used to determine the ripple voltage on 1V5_OUT. The oscilloscope
should be set for the following to take output ripple measurements:
• 1-MΩ impedance
• AC coupling
• 1-μs/division horizontal resolution
• 20-mV/division vertical resolution
TP15 and TP16 can be used to measure the output ripple voltage by placing the oscilloscope probe tip through
TP15 and holding the ground barrel to TP16 as shown in Figure 4-2. For a hands-free approach, the loop in
TP16 can be cut and opened to cradle the probe barrel. Using a leaded ground connection can induce additional
noise due to the large ground loop area.
Test Setup www.ti.com
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4.2 Equipment Setup
Figure 4-2 shows the basic recommended test setup to evaluate the TPS40074EVM-001. Note that although the
return for J1 and J2 are the same, the connections should remain separate as shown in Figure 4-1.
4.2.1 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. An electrostatic smock and safety
glasses should also be worn.
2. Prior to connecting the DC input source, V12V_IN, it is advisable to limit the source current from V12V_IN to
5.0-A maximum. Make sure V12V_IN is initially set to 0 V and connected as shown in Section 4.2.2.
3. Connect the ammeter A1 (0-A to 5-A range) between V12V_IN and J1 as shown in Figure 4-1.
4. Connect voltmeter V1 to TP1 and TP2 as shown in Figure 4-1.
5. Connect LOAD1 to J2 as shown in Figure 3-1. Set LOAD1 to constant current mode to sink 0 ADC before
V12V_IN is applied.
6. Connect voltmeter, V2 across TP17 and TP18 as shown in Figure 4-1.
7. Connect an oscilloscope probe to TP16 and TP15 as shown in Figure 4-2.
8. Place a fan as shown in Figure 4-1. Turn it on, making sure air is flowing across the EVM.
4.2.2 Diagram
LOAD1
1.5V @
15A
-
+
-+
V1
FAN
-1V5_OUT +
+12V_IN -
+-
Oscilloscope
1M!, AC
10mV / div
20MHz
+
+
-
-
A1
V
-
+
12V_IN
TP1 TP2
TP16
TP15
TP5 TP7 TP6
TEXAS INSTRUMENTS
TPS40074EVM-001
12V to 1.5V @ 15A with Remote Sense
HPA095A
J2
J1
V2
+
-
-+
TP18
TP17
GND CHA CHB
See Tip and Barrel
Measurement for
Vout ripple
Figure 4-1. TPS40074EVM-001 Recommended Test Setup
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TP16TP15
Metal Ground Barrel
Probe Tip
Tip and Barrel Vout ripple
measurement
Figure 4-2. Output Ripple Measurement – Tip and Barrel using TP15 and TP16
4.3 Start-Up/Shutdown Procedure
1. Increase V12V_IN (V1) from 0 V to 10 VDC.
2. Vary LOAD1 from 0 A–10 ADC.
3. Vary V12V_IN (V1) from 10 VDC to 14 VDC.
4. Decrease LOAD1 to 0 A.
5. Decrease V12V_IN to 0 V.
4.4 Equipment Shutdown
1. Shut down the oscilloscope.
2. Shut down LOAD1.
3. Shut down V12V_IN.
4. Shut down FAN.
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5 TPS40074EVM Typical Performance Data and Characteristic Curves
Figure 5-1 through Figure 6-2 present typical performance curves for the TPS40074EVM-001. 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.
5.1 Efficiency
TPS40074EVM-001
EFFICIENCY
LOAD CURRENT
vs
70
72
74
76
78
80
82
84
86
88
90
0 2 4 6 8 10 12 14 16
I - Load Current - A
L
Efficiency - %
10
12
14
Revision Tested A
V = 10-14 V,
V = 1.5 V,
I = 0-15 A
12 V_IN
1V5_OUT
1V5_OUT
Figure 5-1. TPS40074EVM-001 Efficiency V12V_IN = 10 V–14 V, V1V5_OUT = 1.5 V, I1V5_OUT = 0 A–15 A
5.2 Line and Load Regulation
TPS40074EVM
LINE AND LOAD REGULATION
1.495
1.5
1.505
1.51
1.515
1.52
1.525
0 2 4 6 8 10 12 14 16
I - Load Current - A
L
V - Output Voltage - V
O
Revision Tested A
14 12
10
Figure 5-2. TPS40074EVM-001 Line and Load Regulation – ±1% Window
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6 EVM Assembly Drawings and Layout
Figure 6-1 through Figure 6-6 show the design of the TPS40074EVM-001 printed circuit board. The EVM
has been designed using a 4-layer, 2-oz copper-clad circuit board 3.0 inch × 3.0 inch with all components
on the top side to allow the user to easily view, probe, and evaluate the TPS40074 control IC in a practical
application. Moving components to both sides of the PCB or using additional internal layers can offer additional
size reduction for space constrained systems.
Figure 6-1. TPS40074EVM-001 Component Placement (Viewed from Top)
Figure 6-2. TPS40074EVM-001 Silkscreen (Viewed from Top)
EVM Assembly Drawings and Layout www.ti.com
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