LM5119_1

LM5119 Evaluation Board LM5119 Evaluation Board National Semiconductor Application Note 2065 Eric Lee September 28, 2010 Introduction The LM5119EVAL evaluation board provides the design engineer with a fully functional dual output buck converter, employing the LM5119 Dual Emulated Current Mode Synchronous Buck Controller. The evaluation board is designed to provide both 10V and 5V outputs over an input range of 14V to 55V. Also the evaluation board can be easily configured for a single 10V, 8A regulator. choose the correct connector and wire size when attaching the source power supply and the load. SOURCE POWER The power supply and cabling must present low impedance to the evaluation board. Insufficient cabling or a high impedance power supply will droop during power supply application with the evaluation board inrush current. If large enough, this droop will cause a chattering condition during power up. During power down, insufficient cabling or a high impedance power supply will overshoot. This overshoot will cause a non-monotonic decay on the output. An additional external bulk input capacitor may be required unless the output voltage droop/overshoot of the source power is less than 0.7V. In this board design, UVLO setting is conservative while UVLO hysteresis setting is aggressive. Minimum input voltage can goes down with an aggressive design. Minimum operating input voltage depends on the output voltage droop/overshoot of the source power supply and the forced off-time of the LM5119. Refer to the LM5119 datasheet for complete design information. LOADING When using an electronic load, it is strongly recommended to power up the evaluation board at light load and then slowly increase the load. If it is desired to power up the evaluation board at maximum load, resistor banks must be used. In general, electronic loads are best suited for monitoring steady state waveforms. AIR FLOW Prolonged operation with high input voltage at full power will cause the MOSFETs to overheat. A fan with a minimum of 200LFM should be always provided. Performance of the Evaluation Board • • • • • • • • Input Voltage Range: 14V to 55V Output Voltage: 10V (CH1), 5V (CH2) Output Current: 4A (CH1), 8A (CH2) Nominal Switching Frequency: 230 KHz Synchronous Buck Operation: Yes Diode Emulation Mode: Yes Hiccup Mode Overload Protection: Yes External VCC Sourcing: Yes Powering and Loading Consideration When applying power to the LM5119 evaluation board, certain precautions need to be followed. A misconnection can damage the assembly. PROPER BOARD CONNECTION The input connections are made to the J1 (VIN) and J2 (RTN/ GND) connectors. The CH1 load is connected to the J3 (OUT1+) and J4 (OUT1-/GND) and the CH2 load is connected to the J6 (OUT2+) and J5 (OUT2-/GND). Be sure to AN-2065 30126006 FIGURE 1. Typical Evaluation Setup © 2010 National Semiconductor Corporation 301260 www.national.com AN-2065 QUICK START-UP PROCEDURE STEP 1: Set the power supply current limit to at least 16A. Connect the power supply to J1 and J2. STEP 2: Connect one load with a 4A capacity between J3 and J4. Connect another load with an 8A capacity between J6 and J5. STEP 3: Set input voltage to 24V and turn it on. STEP 4: Measure the output voltages. CH1 should regulate at 10V and CH2 should regulate at 5V. STEP 5: Slowly increase the load current while monitoring the output voltages. The outputs should remain in regulation up to full load current. STEP 6: Slowly sweep the input voltage from 14V to 55V while monitoring the output voltages. The outputs should remain in regulation. LOAD TRANSIENT Figure 3 shows the transient response for a load of change from 2A to 6A on 5V output. The upper waveform shows output voltage droop and overshoot during the sudden change in output current shown by the lower waveform. Waveforms SOFT START When applying power to the LM5119 evaluation board a certain sequence of events occurs. Soft-start capacitors and other components allow for a linear increase in output voltages. The soft-start time of each output can be controlled independently. Figure 2 shows the output voltage during a typical start-up with a load of 3Ω on the 10V output, and 1Ω on the 5V output, respectively. 30126008 Conditions: Input Voltage = 24VDC Output Current 2A to 6A Traces: Top Trace: 5V Output Voltage, Volt/div = 100mV, AC coupled Bottom Trace: Output Current, Amp/div = 2A Horizontal Resolution = 0.5 ms/div FIGURE 3. Load Transient Response OVERLOAD PROTECTION The evaluation board is configured with hiccup mode overload protection. The restart time can be programmed by C11. Figure 4 shows hiccup mode operation in the event of an output short on CH2 output. One channel may operate in the normal mode while the other is in hiccup mode overload protection. 30126007 Conditions: Input Voltage = 24VDC 3Ω Load on 10V output 1Ω Load on 5V output Traces: Top Trace: 10V Output Voltage, Volt/div = 5V Bottom Trace: 5V Output Voltage, Volt/div = 5V Horizontal Resolution = 1 ms/div FIGURE 2. Start-Up with Resistive Load Conditions: Input Voltage = 24VDC Output Short on 5V Traces: Top Trace: SW Voltage on CH2, Volt/div = 20V Bottom Trace: Inductor Current, Amp/div = 10A Horizontal Resolution = 20 ms/div 30126009 FIGURE 4. Short Circuit www.national.com 2 AN-2065 EXTERNAL CLOCK SYNCHRONIZATION A TP1 (SYNC) test point has been provided on the evaluation board in order to synchronize the internal oscillator to an external clock.Figure 5 shows the synchronized switching operation. Each channel operates 180 degrees out of phase from the other. Performance Characteristics Figure 7 shows the efficiency curves. The efficiency of the power converter is 96% at 24V with full load current. Monitor the current into and out of the evaluation board. Monitor the voltage directly at the input and output terminals of the evaluation board. 30126010 Conditions: Input Voltage = 24VDC 4A on 10V Output 8A on 5V Output Traces: Top Trace: SYNC pulse, Volt/div = 5V Middle Trace: SW voltage on CH1, Volt/div = 10V Bottom Trace: SW voltage on CH2, Volt/div = 10V Horizontal Resolution = 1 µs/div 30126019 FIGURE 7. Typical Efficiency vs Load Current FIGURE 5. Clock Synchronization SHUTDOWN Figure 6 shows the shutdown procedure by powering off the source power. When UVLO pin voltage is less than 1.26V, the switching stops and soft-start capacitors are discharged by internal switches. Board Configuration INTERLEAVED BUCK OPERATION FOR SINGLE 10V 8A OUTPUT The evaluation board is designed to be easily converted to a 10V, 8A single output regulator with the interleaved operation. Proper electronic load connection is shown in Figure 8. Connecting the electronic load at the center of shorting bar is recommended to prevent a voltage difference between CH1 and CH2 output. In order to produce a single 10V output with 8A maximum output current, populate R21 and R22 with 0Ω resistor and open R6, C15 and C14. The electronic load should have over 8A capability to test the interleaved operation. 30126018 Conditions: Input Voltage = 24VDC 1Ω Load on 5V Output Traces: Top Trace: Input Voltage, Volt/div = 20V Middle Trace1: 5V Output, Volt/div = 2V Middle Trace2: VCC, Volt/div = 5V Bottom Trace: SS Voltage, Volt/div = 5V Horizontal Resolution = 20 ms/div 30126020 FIGURE 8. Load Connection for Single Output FIGURE 6. Shutdown 3 www.national.com AN-2065 EXTERNAL VCC SUPPLY & VCC DISABLE External VCC supply helps to reduce the temperature and the power loss of the LM5119 at high input voltage. By populating D3 and D4, VCC can be supplied from an external power supply. Use TP3 as an input of the external VCC supply with 0.1A current limit. R36, R35 and C45 should be populated with proper value when the voltage of the external VCC is smaller than 7V. The voltage at the VCCDIS pin can be monitored at TP2. To prevent a reverse current flow from VCC to VIN through the internal diode, the external VCC voltage should always be lower than VIN. In this LM5119 evaluation board, VCC1 and VCC2 are supplied from the 10V output to achieve high efficiency. LOOP RESPONSE TP5 and TP6 (TP7 and TP8) have been provided in order to measure the loop transfer function of CH1 (CH2). Refer to AN-1889 for detail information about the loop transfer function measurement. 30126022 FIGURE 10. Loop Response Measurement Setup 30126021 FIGURE 9. Efficiency Comparison at 48V with External VCC vs Without External VCC www.national.com 4 AN-2065 Evaluation Board Schematic 30126023 5 www.national.com AN-2065 Bill of Materials Part C1, C2, C3, C4,C5, C32, C35,C36, C37, C38, C39, C40, C41, C42 C6, C7, C25,C29 C8, C10, C14, C16 C9 C11, C18, C19 C12,C13 C15,C17 C20,C21 C22,C26 C23,C24,C27,C28 C30,C31 C33,C34 C43,C44,C45,C46,C47 R1 R2 R3 R4 R5,R16,R21,R22,R35, R36 R6,R7 R8,R9,R23,R24,R31, R32 R10,R12 R11 R13 R14,R15 R17,R37 R18,R20 R25,R26 R27,R28,R29,R30 D1,D2 D3,D4 L1,L2 Q1,Q3, Q2,Q4 U1 J1,J2,J3,J4,J5,J6 TP1,TP2,TP3 TP5,TP6,TP7,TP8 15A Φ0.1 Value 2.2µF, 100V, X7R Package 1210 Part Number C3225X7R2A225K Manufacturer TDK 1µF, 16V, X7R 100pF, 50V, C0G 0.47µF, 100V, X7R 0.47µF, 25V, X7R 0.047µF, 16V, X7R 6800pF, 25V, C0G 820pF, 50V, C0G 470µF, 16V 22µF,16V, X7R 1000pF, 50V, X7R 1000pF,100V, C0G NU 3.9 ohm, 5% 60.4k, 1% 6.19k, 1% 22.1k, 1% NU 36.5k, 1% 10 ohm, 5% 6.98k, 1% 604 ohm, 1% 1.33k, 1% 73.2k, 1% 0 ohm 0.01 ohm, 1W, 1% 5.1 ohm, 1W, 1% 0 ohm 60V, 1A 20V, 1A 15µH, 14A 60V, 100A 0603 0603 0805 0603 0603 0603 0603 Φ10 1210 0603 0805 0805 0805 0603 0603 C1608X7R1C105K C1608C0G1H101J GRM21BR72A474KA73 GRM188R71E474KA12 C1608X7R1C473K C1608C0G1E682J C1608C0G1H821J PCG1C471MCL1GS C3225X7R1C226K C1608X7R1H102K C2012C0G2A102J CRCW08053R90JNEA CRCW080560K4FKEA CRCW06036K19FKEA CRCW060322K1FKEA TDK TDK Murata Murata TDK TDK TDK Nichicon TDK TDK TDK Vishay Vishay Vishay Vishay 0603 0805 0805 0805 0805 0603 0603 0815 2512 0805 SOD123F PowerDI323 18.2x18.3 LFPAK SO-8 LLP32 CRCW060336K5FKEA CRCW080510R0JNEA CRCW08056K98FKEA MCR10EZHF6040 MCR10EZHF1331 CRCW060373K2FKEA MCR03EZPJ000 RL3720WT-R010-F ERJ-1TRQF5R1U MCR10EZPJ000 PMEG6010CEH PD3S120L 74435571500 PSMN5R5-60YS LM5119 7693 5002 1040 Vishay Vishay Vishay Rohm Rohm Vishay Rohm Susumu Panasonic — ECG Rohm NXP Diodes WE NXP NSC Keystone Keystone Keystone www.national.com 6 AN-2065 PCB Layout 30126011 30126012 7 www.national.com AN-2065 30126013 30126014 www.national.com 8 AN-2065 30126015 30126016 9 www.national.com LM5119 Evaluation Board Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: www.national.com Products Amplifiers Audio Clock and Timing Data Converters Interface LVDS Power Management Switching Regulators LDOs LED Lighting Voltage References PowerWise® Solutions Temperature Sensors PLL/VCO www.national.com/amplifiers www.national.com/audio www.national.com/timing www.national.com/adc www.national.com/interface www.national.com/lvds www.national.com/power www.national.com/switchers www.national.com/ldo www.national.com/led www.national.com/vref www.national.com/powerwise WEBENCH® Tools App Notes Reference Designs Samples Eval Boards Packaging Green Compliance Distributors Quality and Reliability Feedback/Support Design Made Easy Design Support www.national.com/webench www.national.com/appnotes www.national.com/refdesigns www.national.com/samples www.national.com/evalboards www.national.com/packaging www.national.com/quality/green www.national.com/contacts www.national.com/quality www.national.com/feedback www.national.com/easy www.national.com/solutions www.national.com/milaero www.national.com/solarmagic www.national.com/training Applications & Markets Mil/Aero PowerWise® Design University Serial Digital Interface (SDI) www.national.com/sdi www.national.com/wireless www.national.com/tempsensors SolarMagic™ THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. NATIONAL MAKES NO REPRESENTATIONS OR WARRANTIES WITH RESPECT TO THE ACCURACY OR COMPLETENESS OF THE CONTENTS OF THIS PUBLICATION AND RESERVES THE RIGHT TO MAKE CHANGES TO SPECIFICATIONS AND PRODUCT DESCRIPTIONS AT ANY TIME WITHOUT NOTICE. NO LICENSE, WHETHER EXPRESS, IMPLIED, ARISING BY ESTOPPEL OR OTHERWISE, TO ANY INTELLECTUAL PROPERTY RIGHTS IS GRANTED BY THIS DOCUMENT. TESTING AND OTHER QUALITY CONTROLS ARE USED TO THE EXTENT NATIONAL DEEMS NECESSARY TO SUPPORT NATIONAL’S PRODUCT WARRANTY. EXCEPT WHERE MANDATED BY GOVERNMENT REQUIREMENTS, TESTING OF ALL PARAMETERS OF EACH PRODUCT IS NOT NECESSARILY PERFORMED. NATIONAL ASSUMES NO LIABILITY FOR APPLICATIONS ASSISTANCE OR BUYER PRODUCT DESIGN. BUYERS ARE RESPONSIBLE FOR THEIR PRODUCTS AND APPLICATIONS USING NATIONAL COMPONENTS. PRIOR TO USING OR DISTRIBUTING ANY PRODUCTS THAT INCLUDE NATIONAL COMPONENTS, BUYERS SHOULD PROVIDE ADEQUATE DESIGN, TESTING AND OPERATING SAFEGUARDS. EXCEPT AS PROVIDED IN NATIONAL’S TERMS AND CONDITIONS OF SALE FOR SUCH PRODUCTS, NATIONAL ASSUMES NO LIABILITY WHATSOEVER, AND NATIONAL DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY RELATING TO THE SALE AND/OR USE OF NATIONAL PRODUCTS INCLUDING LIABILITY OR WARRANTIES RELATING TO FITNESS FOR A PARTICULAR PURPOSE, MERCHANTABILITY, OR INFRINGEMENT OF ANY PATENT, COPYRIGHT OR OTHER INTELLECTUAL PROPERTY RIGHT. LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS PRIOR WRITTEN APPROVAL OF THE CHIEF EXECUTIVE OFFICER AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: Life support devices or systems are devices which (a) are intended for surgical implant into the body, or (b) support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the labeling can be reasonably expected to result in a significant injury to the user. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system or to affect its safety or effectiveness. National Semiconductor and the National Semiconductor logo are registered trademarks of National Semiconductor Corporation. All other brand or product names may be trademarks or registered trademarks of their respective holders. Copyright© 2010 National Semiconductor Corporation AN-2065 For the most current product information visit us at www.national.com National Semiconductor Americas Technical Support Center Email: support@nsc.com Tel: 1-800-272-9959 www.national.com National Semiconductor Europe Technical Support Center Email: europe.support@nsc.com National Semiconductor Asia Pacific Technical Support Center Email: ap.support@nsc.com National Semiconductor Japan Technical Support Center Email: jpn.feedback@nsc.com