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TPS54310EVM
User’s Guide
February 2002PMP EVMs
SLLU037
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications,enhancements, improvements, and other changes to its products and services at any time and to discontinueany product or service without notice. Customers should obtain the latest relevant information before placingorders and should verify that such information is current and complete. All products are sold subject to TI’s termsand conditions of sale supplied at the time of order acknowledgment.
TI warrants performance of its hardware products to the specifications applicable at the time of sale inaccordance with TI’s standard warranty. Testing and other quality control techniques are used to the extent TIdeems necessary to support this warranty. Except where mandated by government requirements, testing of allparameters of each product is not necessarily performed.
TI assumes no liability for applications assistance or customer product design. Customers are responsible fortheir products and applications using TI components. To minimize the risks associated with customer productsand applications, customers should provide adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right,copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or processin which TI products or services are used. Information published by TI regarding third–party products or servicesdoes not constitute a license from TI to use such products or services or a warranty or endorsement thereof.Use of such information may require a license from a third party under the patents or other intellectual propertyof the third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of information in TI data books or data sheets is permissible only if reproduction is withoutalterationand is accompanied by all associated warranties, conditions, limitations, and notices. Reproductionof this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable forsuch altered documentation.
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Texas Instruments (TI) provides the enclosed product(s) under the following conditions:This evaluation kit being sold by TI is intended for use for ENGINEERING DEVELOPMENT OR EVALUATION
PURPOSES ONLY and is not considered by TI to be fit for commercial use. As such, the goods being providedmay not be complete in terms of required design-, marketing-, and/or manufacturing-related protectiveconsiderations, including product safety measures typically found in the end product incorporating the goods.As a prototype, this product does not fall within the scope of the European Union directive on electromagneticcompatibility and therefore may not meet the technical requirements of the directive.
Should this evaluation kit not meet the specifications indicated in the EVM User’s Guide, the kit may be returnedwithin 30 days from the date of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVEWARRANTY MADE BY SELLER TOBUYER AND IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED,IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANYPARTICULAR PURPOSE.
The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the userindemnifies TI from all claims arising from the handling or use of the goods. Please be aware that the productsreceived may not be regulatory compliant or agency certified (FCC, UL, CE, etc.). Due to the open constructionof the product, it is the user’s responsibility to take any and all appropriate precautions with regard to electrostaticdischarge.
EXCEPT TOTHE EXTENT OF THE INDEMNITY SET FORTH ABOVE, NEITHER PARTY SHALL BE LIABLETO THE OTHER FOR ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.
TI currently deals with a variety of customers for products, and therefore our arrangement with the user is notexclusive.
TI assumes no liability for applications assistance, customer product design, software performance, orinfringement of patents or services described herein.
Please read the EVM User’s Guide and, specifically, the EVM Warnings and Restrictions notice in the EVMUser’s Guide prior to handling the product. This notice contains important safety information about temperaturesand voltages. For further safety concerns, please contact the TI application engineer.
Persons handling the product must have electronics training and observe good laboratory practice standards.No license is granted under any patent right or other intellectual property right of TI covering or relating to any
machine, process, or combination in which such TI products or services might be or are used.
This EVM is designed to operate over an input voltage range of 4.0 V to 6.0 V, and over a loadrange of 0 A to 3 A.
It is important to operate this EVM within the specified input and output ranges described inthe EVM User’s Guide.
Exceeding the specified input range may cause unexpected operation and/or irreversibledamage to the EVM. If there are questions concerning the input range, please contact a TIfield representative prior to connecting the input power.
Applying loads outside of the specified output range may result in unintended operation and/orpossible permanent damage to the EVM. Please consult the EVM User’s Guide prior toconnecting any load to the EVM output. If there is uncertainty as to the load specification,please contact a TI field representative.
During normal operation, some circuit components may have case temperatures greater than60°C. The EVM is designed to operate properly with certain components above 60°C as longas the input and output ranges are maintained. These components include but are not limitedto linear regulators, switching transistors, pass transistors, and current sense resistors. Thesetypes of devices can be identified using the EVM schematic located in the EVM User’s Guide.When placing measurement probes near these devices during operation, please be awarethat these devices may be very warm to the touch.
This chapter contains background information for the TPS54310 and supportdocumentation for the TPS54310 evaluation module. The EVM performancespecifications are also given.
The TPS54310 evaluation module (EVM) uses the TPS54310 synchronousbuck regulator to provide a 3.3-V output over an input range of 4.0 V to 6.0 V,and over a load range of 0 A to 3 A. Less than0.55 square inches of boardspace is occupied bythe electrical components of the TPS54310 circuit.Additional pads support multiple input and ouput capacitors. A jumper allowsthe switching frequency to be easily changed from 350 kHz to 550 kHz.
The MOSFETs of the TPS54310 are incorporated inside the TPS54310package. This eliminates the need for external MOSFETs and their associateddrivers. The low drain-to-source on resistance of the MOSFETs gives theTPS54310 high efficiency and helps to keep the junction temperature low athigh output currents. The compensation components, external to the IC, allowfor an adjustable output voltage and a customizable loop reponse.
1.2Performance Specification Summary
Table 1–1 provides a summary of the TPS54310 EVM performancespecifications. All specifications are given for an ambient temperature of 25°C,unless otherwise noted.
Table 1–1.Performance Specification Summary
SpecificationTest ConditionsMinTypMaxUnitsInput voltage range4.05.06.0VOutput voltage set point3.3VOutput current rangeVIN = 5 V03ALoad regulationVIN = 5 V–77mV
Transient response time is defined as the time elapsed from the onset of the transient to the time that the output returns within±2% of its steady state value.
1-2
1.3Modifications
1.3.1General
The TPS54310 EVM is designed to demonstrate the small amount of boardspace taken up by the TPS54310 electrical components. In addition, the EVMcan be used to evaluate different output filters by substituting an alternateinductor for L1, or by using the optional pads for capacitors C2 and C11 (seeFigure 3–1). When changing the output filter, the compensation values mustalso be changed to ensure that stability is maintained. The SWIFT Designersoftware tool or Texas Instruments application note SLVA109 can be used toassist in the calculation of compensation components. Both SWIFT Designerand SLVA109 are available for download at the Texas Instruments web site.
1.3.2Switching Frequency
The TPS54310 is configured to switch at a frequency of 700 kHz. Alternatively,the EVM can be easily configured to switch at either 350 kHz or 550 kHz byremoving the frequency trimming resistor R3, and placing the shunt on jumperJP1 in the proper location. Also, by changing the value of RT (R3), the switch-ing frequency can be trimmed to any value between 280 kHz and 700 kHz. Aplot of the value of RT versus the switching frequency is given in Figure 1–1.
The output voltage of the TPS54310 EVM can be adjusted to any value downto 0.9 V by changing only one component value (R4). The value of R4 for aspecific output voltage can be calculated by using equation 1–1. Table 1–2lists the value of R4 for some common bus voltages.
R4+10kW
Table 1–2.Output Voltage Programming
Output Voltage
(V)
0.91000
1.228.7
1.514.7
1.89.76
2.55.49
3.33.74
1.3.4Slow Start
The slow start time of the EVM can be modified by changing the value of C1.Use equation 1–2 to calculate the value of C1 for a specific slow start time. WithC1 open, the slow start time is typically 3.6 ms. The slow start time can not bemade faster than 3.6 ms.
0.891V
VO–0.891V
(1–1)
R4
(kΩ)
TSS5mA
C
+
1
0.891V
1.3.5Improving Transient Response
The feedback compensation components are R2, R4, R5, R6, C4, C5, and C6(see Figure 4–1), and were selected based on the output of the SWIFTDesigner software tool. This results in a unity gain bandwidth of 30 kHz, anda phase margin of 95° (see Figure 2–8). The TPS54310 EVM responds to a3-A load transient within 30 µs using the compensation shown in theschematic. While this response time is more than sufficient for mostapplications, the response time can be made faster by changing the values ofthe feedback compensation components. Using the values given byTable 1–3, the unity gain bandwidth is increased to 75 kHz, and the phasemargin is 72° (see Figure 2–9). With this alternate compensation, the outputvoltage remains within a ±2% regulation band during a 3-A load transient (seeFigure2–7).
(1–2)
1-4
Performance Specification Summary
Table 1–3.Alternate Compensation for Improved Transient Response
This chapter describes how to properly connect, setup, and use the TPS54310EVM. It also presents the test results and covers efficiency, output voltageregulation, load transients, loop response, output ripple, input ripple, andstart-up.
The TPS54310 EVM has the following four input/output connections: J1 (Vand GND) and J3 (Vis shown in Figure 2–1. Connect a power supply capable of supplying 3 A toJ1 through a pair of 20 AWG wires. Connect the load to J3 through a pair of20 AWG wires. Minimize wire lengths to reduce losses in the wires. Test pointTP8 provides easy connection for an oscilloscope voltage probe to monitor theoutput voltage.
Figure 2–1.Connection Diagram
and GND). A diagram showing the connection points
out
in
2-2
2.2Loop Characterization Setup
The TPS54310 EVM contains a 49.9 Ω resistor (R7) in the feedback path foruse in measuring the loop response. Test points on either side of R7 (TP5 andTP7) provide connection points for network analyzer signals. By injecting asmall ac signal across R7, the loop gain and phase can be measured from oneside of R7 to the other. Because the value of R7 is small in relation to the valueof R5, it does not significantly affect the output voltage set point of theregulator.
2.3Efficiency
The TPS54310 EVM efficiency peaks at around 1 A of load current. At full loadthis drops to around 90.5%. Figure 2–2 shows the typical efficiency for a 5-Vinput and an ambient temperature of 25ambient temperatures due to temperature variation in the drain-to-sourceresistance of the MOSFETs. The efficiency is also slightly higher at lowerswitching frequencies due to the gate and switching losses in the MOSFETs.The total board losses are shown in Figure 2–3.
Figure 2–2.Measured Efficiency
96
TA = 25°CVI = 5 V
94
Loop Characterization Setup
°
C. The efficiency is lower at higher
92
90
88
Efficency – %
86
84
82
80
00.511.522.53
IL– Load Current – A
Test Setup and Results
2-3
Thermal Performance
Figure 2–3.Measured Board Losses
1.2
1
0.8
0.6
Losses – W
0.4
0.2
0
00.511.522.53
2.4Thermal Performance
TA = 25°CVI = 5 V
IL– Load Current – A
The junction temperature is plotted versus the load current with a 5-V inputvoltage and a 25°C ambient temperature in Figure 2–4. The low junction-to-case thermal resistance of the PWP package, along with a good board layout,helps to keep the junction temperature low at high output currents. With a 5-Vinput source and a 3-A load, the junction temperture is approximately 47
Figure 2–4.Measured Junction Temperature at 25°C Ambient
50
TA = 25°CVI = 5 V
45
C
°
40
35
30
– Junction Temperature –
J
T
25
20
00.511.522.53
IL– Load Current – A
°
C.
2-4
2.5Output Voltage Regulation
The output voltage load regulation, with a 5-V input and a 25°C ambienttemperature, is shown in Figure 2–5. Over the load range of 0 A to 3 A, theoutput voltage varies less than 0.2%.
Figure 2–5.Measured Load Regulation
1.01
1.008
1.006
1.004
1.002
1
0.998
– Output Voltage – V
0.996
O
V
(Normalized to 1.5 A Load)
0.994
0.992
Output Voltage Regulation
TA = 25°CVI = 5 V
0.9900.511.522.53
IL– Load Current – A
Test Setup and Results
2-5
Load Transients
2.6Load Transients
The TPS54310 EVM response to load transients is shown in Figure 2–6. Theload transient in Figure 2–6 transitions between 0 A and 3 A. The outputvoltage deviates approximately –95 mV (–2.9%) and 75 mV (2.3%) from itsaverage value as a result of these transients. In Figure 2–6, the output voltagereturns to a ±2% regulation band within 30 µs. Using the alternate feedbackcompensation described in Section 1.3.5 Improving Transient Response, theoutput voltage deviation can be reduced to –55 mV (–1.7%) and 45 mV (1.4%),as shown in Figure 2–7. With the alternate compensation, the output voltageremains within a ±2% regulation band through the duration of the loadtransient.
Figure 2–6.Measured Load Transient Response
VI = 5 V40 µs/div
VO (AC)50 mV/div
Figure 2–7.Improved Load Transient Response
VI = 5 V20 µs/div
IO2 A/div
VO (AC)50 mV/div
IO2 A/div
2-6
2.7Loop Characteristics
The loop gain and phase for a 5.0-V input and a 3.0-A load is shown inFigure 2–8. The loop crossover frequency is approximately 30 kHz, and thephase margin is approximately 75the alternate compensation described in Section 1.3.5 Improving TransientResponse. With the alternate feedback compensation, the loop crossoverfrequency is approximately 75 kHz, and the phase margin is approximately72°.
Figure 2–8.Improved Loop Gain and Phase
Loop Characteristics
°
. Figure 2–9 shows the loop response using
60
TA = 25°CVI = 5 V
40
20
Gain – dB
0
–20
1001 k10 k100 k1 M
Phase
Gain
f – Frequency – Hz
Figure 2–9.Measured Loop Gain and Phase for Alternate Compensation
60
TA = 25°CVI = 5 V
135
90
45
Phase – Degrees
0
–45
135
Phase
40
20
Gain – dB
0
–20
1001 k10 k100 k1 M
Gain
f – Frequency – Hz
Test Setup and Results
90
45
Phase – Degrees
0
–45
2-7
Output Voltage Ripple
2.8Output Voltage Ripple
The output ripple voltage is plotted in Figure 2–10 with an input voltage of 5.0Vand a load current of 3 A. The TPS54310 EVM has a typical output voltageripple of less than 33 mVripple voltage is higher. The output ripple voltage can be decreased by usinga larger inductor, or by reducing the equivalent series resistance of the outputcapacitor. Changing either of these components requires the feedbackcompensation to be redesigned.
Figure 2–10.Measured Output Voltage Ripple
VI = 5 VIO = 3 A400 ns/div
pp
. If the switching frequency is reduced, the output
VO (AC)10 mV/div
2-8
2.9Input Ripple Voltage
The input ripple voltage for a 3-A load is shown in Figure 2–11. With an inputvoltage of 5.0 V, the input ripple is approximately 120 mVvoltage can be made lower by adding capacitance to the input.
Figure 2–11.Measured Input Voltage Ripple
VI = 5 VIO = 3 A400 ns/div
Input Ripple Voltage
. The input ripple
pp
VI (AC)50 mV/div
Test Setup and Results
2-9
Start-Up
2.10Start-Up
Figure 2–12 shows the start-up voltage waveform of the TPS54310 EVM withC1 left open. The input voltage is displayed on channel 3, the output voltageon channel 1, and the power good signal on channel 2. Once the input voltagerises above the 2.9-V start-up threshold, the output voltage begins to riselinearly to 3.3 V in 3.6 ms. When the output voltage has reached its final value,the open-drain power good signal rises to a high state. The start-up time canbe extended by using an external slow-start capacitor, C1. To program aspecific slow start time, see Section 1.3.4 Slow Start.
The shorting jumper on J2 should not be used to enable the EVM, as this maycause excessive voltage transients on the SS/ENA pin. Use an externalenable signal instead of the J2 jumper.
Figure 2–12.Measured Start-Up Waveforms
VI (2 V/div)
3
1
2
VO (2 V/div)
V
(PWRGD)
(5 V/div)
1 ms/div
2-10
Chapter 3
Board Layout
This chapter provides a description of the TPS54310 EVM board layout andlayer illustrations.
The top-side layer for the TPS54310 EVM is shown in Figure 3–1. The inputcapacitors (C8 and C9), bias decoupling capacitor (C3), and bootstrapcapacitor (C7), are all located as close to the IC as possible. In addition, thefeedback compensation components are also kept close to the IC. Thecompensation circuit ties to the output voltage at the point of regulation (TP7).
The TPS54310 EVM PWB consists of two layers of 1.5 oz. copper. The bottomhalf of the top layer is used as a power ground plane, while the bottom layeris used as a quiet (analog) ground plane. The two ground planes tie togetherat U1 to reduce the noise injected between the two IC ground connections. Atotal of 10 vias are used to tie the thermal land area under the TPS54310device to the thermal plane on the backside of the board.
Figure 3–1.Top Side Assembly
3-2
Figure 3–2.Bottom Side Assembly
Layout
Board Layout
3-3
Layout
Figure 3–3.Top Side Layout
3-4
Figure 3–4.Bottom Side Layout
Layout
Board Layout
3-5
3-6
Chapter 4
Schematic and Bill of Materials
The EVM schematic and bill of materials are presented in this chapter.
TP72TP2, TP6Test point, black, 1 mm0.038”Farnell240–3331TP8Adaptor, 3,5 mm probe clip ( or 131–5031–00)0.200”Tektronix131–4244–001U1IC, SWIFT power controller, Adj V,3 APWP20TITPS54310PWP1––PCB, 3 In x 3 In x 0.062 InAnySLVP2012––Shunt, 100 mil, black0.1003M929950–00
Test point, red, 1 mm0.038”Farnell240–345
Schematic and Bill of Materials
4-3
4-4
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