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User's Guide

SLVU356–January 2010

Using the TPS54291EVM-431 A 12V Input, 3.3V 1.5A and

1.2V 2.5A Synchronous Buck Converter

Contents

1 Introduction .................................................................................................................. 2

1.1 Description .......................................................................................................... 2

1.2 Applications ......................................................................................................... 2

1.3 Features ............................................................................................................. 2

2 TPS54291EVM-431 Electrical Performance Specifications ........................................................... 3

3 Schematic .................................................................................................................... 4

3.1 Enable Jumpers (JP1 and JP2) .................................................................................. 5

3.2 Error Amplifier Outputs ............................................................................................ 5

3.3 Test Point Descriptions ............................................................................................ 5

4 Test Set UP .................................................................................................................. 6

4.1 Equipment ........................................................................................................... 6

4.2 Equipment Setup ................................................................................................... 7

4.3 Start Up / Shut Down Procedure ................................................................................. 9

4.4 Output Ripple Voltage Measurement Procedure ............................................................. 10

4.5 Control Loop Gain and Phase Measurement Procedure .................................................... 10

4.6 Equipment Shutdown ............................................................................................ 10

5 TPS54291EVM-431 Typical Performance Data and Characteristic Curves ....................................... 10

5.1 Efficiency .......................................................................................................... 11

5.2 Line and Load Regulation ....................................................................................... 11

5.3 Switch Node and Output Ripple Voltage ...................................................................... 12

6 EVM Assembly Drawings and Layout .................................................................................. 12

7 List of Materials ............................................................................................................ 16

List of Figures

1 TPS54291EVM-431 Schematic (For Reference Only, See Table 4: Bill of Materials for Specific Values) ..... 4

2 TPS54291EVM-431 Recommended Test Set-Up ...................................................................... 8

3 Output Ripple Measurement – Tip and Barrel using TP3 and TP4 or TP18 and TP19 ........................... 9

4 Control Loop Measurement Setup........................................................................................ 9

5 TPS54291EVM-431 Efficiency vs Load Current ...................................................................... 11

6 TPS54291EVM-431 Output Voltage vs Load Current ................................................................ 11

7 TPS54291EVM-431 Output Voltage Ripple ........................................................................... 12

8 TPS54291EVM-431 Component Placement (Viewed from Top).................................................... 12

9 TPS54291EVM-431 Silkscreen (Viewed from Top)................................................................... 13

10 TPS54291EVM-431 Top Copper (Viewed from Top)................................................................. 13

11 TPS54291EVM-431 Bottom Copper (X-Ray View from Top)........................................................ 14

12 TPS54291EVM-431 Internal 1 (X-Ray View from Top) .............................................................. 14

13 TPS54291EVM-431 Internal 2 (X-Ray View from Top) .............................................................. 15

List of Tables

1 TPS54291EVM-431 Electrical and Performance Specifications...................................................... 3

SLVU356–January 2010 Using the TPS54291EVM-431 A 12V Input, 3.3V 1.5A and 1.2V 2.5A

Synchronous Buck Converter

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Summary of content (17 pages)

PAGE 1
User's Guide SLVU356 – January 2010 Using the TPS54291EVM-431 A 12V Input, 3.3V 1.5A and 1.2V 2.5A Synchronous Buck Converter 1 2 3 4 5 6 7 Contents Introduction .................................................................................................................. 2 1.1 Description .......................................................................................................... 2 1.2 Applications ....................................................................................
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Introduction 1 www.ti.com 2 Test Point Descriptions ..................................................................................................... 5 3 TPS54291EVM-431 Bill of Materials .................................................................................... 16 Introduction The TPS54291EVM-431 evaluation module (EVM) is a dual synchronous buck converter providing fixed 3.3V and 1.2V outputs at up to 1.5A and 2.5A respectively from a 12V bus.
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TPS54291EVM-431 Electrical Performance Specifications www.ti.com 2 TPS54291EVM-431 Electrical Performance Specifications Table 1. TPS54291EVM-431 Electrical and Performance Specifications Parameter Notes and Conditions Min Nom Max Units V INPUT CHARACTERISTICS VIN Input Voltage 9.6 12 13.2 IIN Input Current VIN = Nom, IOUT = Max – 2.4 2.6 A No Load Input Current VIN = Nom, IOUT = 0 A – 12 20 mA Input UVLO IOUT = Min to Max 4.0 4.2 4.
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Schematic Schematic + 3 www.ti.com Figure 1. TPS54291EVM-431 Schematic (For Reference Only, See Table 4: Bill of Materials for Specific Values) 4 Using the TPS54291EVM-431 A 12V Input, 3.3V 1.5A and 1.2V 2.
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Schematic www.ti.com 3.1 Enable Jumpers (JP1 and JP2) TPS54291EVM-431 provides separate 3 pin 100-mil headers and shunts for exercising the TPS54291 Enable functions. Place the JP1 shunt in the Left Position connects EN1 to ground and turns on Output 1 and placing the JP2 shunt in the Left Position connects EN2 to ground and turns on Output 2. 3.
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Test Set UP 3.3.3 www.ti.com Channel 1 Loop Analysis (TP5, TP6, TP7 and TP8) TPS54291EVM-431 contains a 51Ω series resistor (R1) in the feedback loop to allow for matched impedance signal injection into the feedback for loop response analysis. An isolation transformer should be used to apply a small (30mV or less) signal across R1 through TP6 and TP8. By monitoring the AC injection level at TP8 and the returned AC level at TP6, the power supply loop response can be determined. 3.3.
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Test Set UP www.ti.com V1: VIN, 0-15V voltmeter V2: VOUT1 0-6V voltmeter V3: VOUT2 0-4V voltmeter 4.1.3 Loads LOAD1 The Output1 Load (LOAD1) should be an Electronic Constant Current Mode Load capable of 0-1.5Adc at 3.3V LOAD2 The Output2 Load (LOAD2) should be an Electronic Constant Current Mode Load capable of 0-2.5Adc at 1.2V 4.1.4 Oscilloscope OSCILLOSCOPE A Digital or Analog Oscilloscope can be used to measure the ripple voltage on VOUT1 or VOUT2.
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Test Set UP www.ti.com maximum. Make sure VIN is initially set to 0V and connected as shown in Figure 2. 3. Connect the ammeter A1 (0-5A range) between VIN and J1 as shown in Figure 2. 4. Connect voltmeter V1 to TP1 and TP2 as shown in Figure 2. 5. Connect LOAD1 to J2 as shown in Figure 2. Set LOAD1 to constant current mode to sink 0Adc before VIN is applied. 6. Connect voltmeter, V2 across TP3 and TP4 as shown in Figure 2. 7. Connect LOAD2 to J3 as shown in Figure 2.
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Test Set UP www.ti.com Metal Ground Barrel Probe Tip TP3 / TP4 / TP18 TP19 Tip and Barrel Vout ripple measurement Figure 3. Output Ripple Measurement – Tip and Barrel using TP3 and TP4 or TP18 and TP19 Network Analyzer FAN Isolation Transformer + V3 + + A1 - - - VVIN + V1 LOAD2 1.2V @ 2.5A + LOAD1 3.3V @ 1.5A - + V2 Figure 4. Control Loop Measurement Setup 4.3 Start Up / Shut Down Procedure 1.
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TPS54291EVM-431 Typical Performance Data and Characteristic Curves 2. 3. 4. 5. 6. 7. 4.4 www.ti.com Vary LOAD1 from 0 – 1.5Adc Vary LOAD2 from 0 – 2.5Adc Vary VIN from 9.6Vdc to 13.2Vdc Decrease VIN to 0Vdc Decrease LOAD1 to 0A Decrease LOAD2 to 0A Output Ripple Voltage Measurement Procedure See Section 5.4 for more information on measuring output ripple. 1. Increase VIN from 0V to 12Vdc 2. Adjust LOAD1 to desired load between 0Adc and 1.5Adc 3. Adjust LOAD2 to desired load between 0Adc and 2.5Adc 4.
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TPS54291EVM-431 Typical Performance Data and Characteristic Curves www.ti.com 5.1 Efficiency 100 90 8V 8V 12 V 95 12 V 85 14 V 85 η - Efficiency - % η - Efficiency - % 90 80 75 80 14 V 75 70 70 65 65 60 0 0.2 0.4 0.6 0.8 1 1.2 ILOAD - Load Current - A 1.4 60 1.6 0 0.5 1 1.5 2 ILOAD - Load Current - A 2.5 3 VIN = 9.6-13.2V, VOUT1 = 3.3V IOUT1 = 0-1.5A, VOUT2 = 1.2V IOUT2 = 0-2.5A Figure 5. TPS54291EVM-431 Efficiency vs Load Current 5.2 Line and Load Regulation 1.212 3.35 3.
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EVM Assembly Drawings and Layout 5.3 www.ti.com Switch Node and Output Ripple Voltage VIN = 13.2V, VOUT1 = 3.3A, IOUT2 = 1.2V IOUT2 = 2.5A Ch1: TP3 (VOUT1), Ch2: TP18 (VOUT2) Ch3: TP9 (SW1), Ch4: TP12 (SW2) Figure 7. TPS54291EVM-431 Output Voltage Ripple 6 EVM Assembly Drawings and Layout Figure 8 through Figure 13 show the designs of the TPS54291EVM-431 printed circuit board. The EVM has been designed using a 4-Layer, 2oz copper-clad circuit board 3.0” × 3.0” with all components in a 0.86" × 1.
PAGE 13
EVM Assembly Drawings and Layout www.ti.com Figure 9. TPS54291EVM-431 Silkscreen (Viewed from Top) Figure 10. TPS54291EVM-431 Top Copper (Viewed from Top) SLVU356 – January 2010 Submit Documentation Feedback Using the TPS54291EVM-431 A 12V Input, 3.3V 1.5A and 1.2V 2.
PAGE 14
EVM Assembly Drawings and Layout www.ti.com Figure 11. TPS54291EVM-431 Bottom Copper (X-Ray View from Top) Figure 12. TPS54291EVM-431 Internal 1 (X-Ray View from Top) 14 Using the TPS54291EVM-431 A 12V Input, 3.3V 1.5A and 1.2V 2.
PAGE 15
EVM Assembly Drawings and Layout www.ti.com Figure 13. TPS54291EVM-431 Internal 2 (X-Ray View from Top) SLVU356 – January 2010 Submit Documentation Feedback Using the TPS54291EVM-431 A 12V Input, 3.3V 1.5A and 1.2V 2.
PAGE 16
List of Materials 7 www.ti.com List of Materials Table 3 lists the EVM components as configured according to the schematic shown in Figure 1. Table 3. TPS54291EVM-431 Bill of Materials QTY 16 RefDes Value Description Size Part Number MFR 1 C1 100 μF Capacitor, Aluminum, 25V, ±20% 0.328 x 0.390 inch EEEFC1E101P Panasonic 1 C12 4.7 μF Capacitor, Ceramic, 10V, X5R, 20% 0805 Std Std 2 C2, C14 22 μF Capacitor, Ceramic, 6.
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