LM25116EVAL/NOPB

User's Guide SNVA232A – April 2007 – Revised April 2013 AN-1617 LM25116 Evaluation Board 1 Introduction The LM25116 evaluation board is designed to provide the design engineer with a fully functional power converter based on Emulated Current Mode Control to evaluate the LM25116 controller IC. The evaluation board provides a 5V output with a 7A current capability. The wide input voltage ranges from 7V to 42V. The design operates at 250kHz, a good compromise between conversion efficiency and solution size. The printed circuit board consists of 4 layers, 2 ounce copper top and bottom, 1 ounce copper internal layers on FR4 material with a thickness of 0.06 inches. This user's guide contains the evaluation board schematic, Bill-of-Materials (BOM), and a quick setup procedure. For complete circuit design information, see LM25116 Wide Range Synchronous Buck Controller (SNVS509). The performance of the evaluation board is: • Input Range: 7V to 42 • Output Voltage: 5V • Output Current: 0 to 7A • Frequency of Operation: 250 kHz • Board Size: 2.55 × 2.65 × 0.5 inches • Load Regulation: 1% • Line Regulation: 0.1% • Over Current Limiting Figure 1. Efficiency with 6 µH Cooper Inductor Figure 2. Efficiency with 5.6 µH Pulse Inductor All trademarks are the property of their respective owners. SNVA232A – April 2007 – Revised April 2013 Submit Documentation Feedback AN-1617 LM25116 Evaluation Board Copyright © 2007–2013, Texas Instruments Incorporated 1 Powering and Loading Considerations 2 www.ti.com Powering and Loading Considerations Read this entire section prior to attempting to power the evaluation board. 2.1 Quick Setup Procedure Step 1: Set the power supply current limit to 15A. Turn off the power supply. Connect the power supply to the VIN terminals. Step 2: Connect the load, with a 7A capability, to the VOUT terminals. Positive connection to P3 and negative connection to P4. Step 3: The EN pin should be left open for normal operation. Step 4: Set VIN to 24V with no load applied. VOUT should be in regulation with a nominal 5V output. Step 5: Slowly increase the load while monitoring the output voltage, VOUT should remain in regulation with a nominal 5V output as the load is increased up to 7 Amps. Step 6: Slowly sweep the input voltage from 7 to 42V, VOUT should remain in regulation with a nominal 5V output. Step 7: Temporally short the EN pin to GND to check the shutdown function. Step 8: Increase the load beyond the normal range to check current limiting. The output current should limit at approximately 11A. Cooling is critical during this step. 2.2 Air Flow Prolonged operation with high input voltage at full power will cause the MOSFETs to overheat. A fan with a minimum of 200 LFM should always be provided. Figure 3. Temperature Rise at 24VIN with 6 µH Cooper Inductor 2 Figure 4. Temperature Rise at 24VIN with 5.6 µH Pulse Inductor AN-1617 LM25116 Evaluation Board SNVA232A – April 2007 – Revised April 2013 Submit Documentation Feedback Copyright © 2007–2013, Texas Instruments Incorporated Powering and Loading Considerations www.ti.com 2.3 Powering Up Using the enable pin provided will allow powering up the source supply with the current level set low. It is suggested that the load be kept low during the first power up. Set the current limit of the source supply to provide about 1.5 times the anticipated wattage of the load. As you remove the connection from the enable pin to ground, immediately check for 5 volts at the output. A quick efficiency check is the best way to confirm that everything is operating properly. If something is amiss you can be reasonably sure that it will affect the efficiency adversely. Few parameters can be incorrect in a switching power supply without creating losses and potentially damaging heat. For operation at 7VIN with full load, a 100 µF aluminum electrolytic capacitor installed across VIN will prevent input filter oscillation for a typical bench test setup. For complete design information, see LM25116 Wide Range Synchronous Buck Controller (SNVS509. 2.4 Over Current Protection The evaluation board is configured with over-current protection. The output current is limited to approximately 11A. The thermal stress is quite severe while in an overloaded condition. Limit the duration of the overload and provide sufficient cooling (airflow). Figure 5. Short Circuit at 24VIN Room Temperature Figure 6. Short Circuit at 24VIN 125°C For sustained short circuit protection, adding C7 ≥ 1 µF will limit the short circuit power dissipation. D2 should be installed when using C7. Figure 7. Short Circuit Recovery into Resistive Load with C7 = 1 µF and D2 Installed SNVA232A – April 2007 – Revised April 2013 Submit Documentation Feedback AN-1617 LM25116 Evaluation Board Copyright © 2007–2013, Texas Instruments Incorporated 3 Powering and Loading Considerations 2.5 www.ti.com VCCX This test point supports evaluation of an auxiliary supply voltage derived from VOUT. For output voltages between 7V and 14V, a zero ohm resistor may be installed for R12. The selected MOSFETs need greater than 6V gate drive to fully enhance them for lowest RDS(ON), so R12 is not recommended for the 5V output. Under no circumstances should an external voltage source be connected to VCCX when VIN < VCC. Damage to the controller will result. A series diode from the input voltage source to pin 1 is required to accommodate VIN < VCC. 2.6 Synchronization A SYNC pin has been provided on the evaluation board. This pin can be used to synchronize the regulator to an external clock. For complete information, see LM25116 Wide Range Synchronous Buck Controller (SNVS509). Figure 8. Synchronization at 12VIN 2.7 Active Loads Figure 9 shows a typical start-up characteristic into a constant current active load. This type of load can exhibit an initial short circuit, which is sustained well beyond the normal soft-start cycle. Overshoot of the output voltage is possible with this condition. Increasing the soft-start time to be longer than the initial short circuit period of the active load will minimize any possible overshoot. When using C7, the hiccup offtime may also need adjustment. Figure 9. Start-up into Active Load at 24VIN 4 AN-1617 LM25116 Evaluation Board SNVA232A – April 2007 – Revised April 2013 Submit Documentation Feedback Copyright © 2007–2013, Texas Instruments Incorporated Typical Performance Waveforms www.ti.com 3 Typical Performance Waveforms Figure 10. Full Synchronous Operation at 24VIN with JMP1 Removed Figure 11. Discontinuous Operation using Diode Emulation Mode at 24VIN with JMP1 Installed Figure 12. Transient Response at 24VIN SNVA232A – April 2007 – Revised April 2013 Submit Documentation Feedback AN-1617 LM25116 Evaluation Board Copyright © 2007–2013, Texas Instruments Incorporated 5 Bill of Materials 4 www.ti.com Bill of Materials Item Part Number Type Size Parameters Qty Vendor C1, C2, C14 C2012X7R1E105K Capacitor, Ceramic 0805 1µF, 25V, X7R 3 TDK C3 VJ0603Y103KXAAT Capacitor, Ceramic 0603 0.01µF, 50V, X7R 1 Vishay C4 VJ0603A271JXAAT Capacitor, Ceramic 0603 270pF, 50V, COG, 5% 1 Vishay C5, C15 VJ0603Y101KXATW 1BC Capacitor, Ceramic 0603 100pF, 50V, X7R 1 Vishay C6 VJ0603Y332KXXAT Capacitor, Ceramic 0603 3300pF, 25V, X7R 1 Vishay Capacitor, Ceramic 0603 Not Used 0 2.2µF, 100V X7R 4 TDK C7 C8, C9, C10, C11 C4532X7R2A225M Capacitor, Ceramic 1812 C12 C3225X7R2A105M Capacitor, Ceramic 1210 1µF, 100V X7R 1 TDK C13 C2012X7R2A104M Capacitor, Ceramic 0805 0.1µF, 100V X7R 1 TDK C16, C17, C18, C19, C20 C4532X6S0J107M Capacitor, Ceramic 1812 100µF, 6.3V, X6S, 105°C 5 TDK C21, C22 Capacitor, Tantalum D Case Not Used 0 C23 Capacitor, Ceramic 0805 Not Used 0 D1 CMPD2003 Diode, Switching SOT-23 200mA, 200V 1 Central Semi D2 CMPD2003 Diode, Switching SOT-23 Not Used 0 Central Semi JMP1 Connector, Jumper 2 pin sq. post 1 L1 PD0120.532 Inductor 5.6µH, 10.4A 0 Pulse L1A HC2LP-6R0 Inductor 6µH, 16.5A 1 Cooper 5.6µH, 17A L1A P7611-5R6M Inductor 0 Profec P1-P4 1514-2 Turret Terminal .090” dia. 4 Keystone TP1-TP5 5012 Test Point .040” dia. 5 Keystone Q1, Q2 Si7850DP N-CH MOSFET SO-8 Power PAK 10.3A, 60V 2 Vishay Siliconix R1 CRCW06031023F Resistor 0603 102kΩ, 1% 1 Vishay R2 CRCW06032102F Resistor 0603 21.0kΩ, 1% 1 Vishay R3 CRCW06033741F Resistor 0603 3.74kΩ, 1% 1 Vishay R4 CRCW06031211F Resistor 0603 1.21kΩ, 1% 1 Vishay Resistor 0603 Not Used 0 R5 R6, R7 CRCW06030R0J Resistor 0603 0Ω 2 Vishay R8 CRCW0603103J Resistor 0603 10kΩ, 5% 1 Vishay R9 CRCW06031242F Resistor 0603 12.4kΩ, 1% 1 Vishay R10 CRCW0603183J Resistor 0603 18kΩ, 5% 1 Vishay R11 LRC-LRF2010-01R010-F Resistor 2010 0.010Ω, 1% 0 IRC R11 WSL2010R0100FEA Resistor 2010 0.010Ω, 1% 1 Vishay Resistor 0603 Not Used 0 Resistor 0603 1MΩ, 5% 1 Resistor 1206 Not Used 0 Synchronous Buck Controller HTSSOP-20EP R12 R13 CRCW0603105J R14 U1 6 LM25116 AN-1617 LM25116 Evaluation Board 1 Vishay Texas Instruments SNVA232A – April 2007 – Revised April 2013 Submit Documentation Feedback Copyright © 2007–2013, Texas Instruments Incorporated PCB Layout www.ti.com 5 PCB Layout SNVA232A – April 2007 – Revised April 2013 Submit Documentation Feedback AN-1617 LM25116 Evaluation Board Copyright © 2007–2013, Texas Instruments Incorporated 7 PCB Layout 8 www.ti.com AN-1617 LM25116 Evaluation Board SNVA232A – April 2007 – Revised April 2013 Submit Documentation Feedback Copyright © 2007–2013, Texas Instruments Incorporated PCB Layout www.ti.com SNVA232A – April 2007 – Revised April 2013 Submit Documentation Feedback AN-1617 LM25116 Evaluation Board Copyright © 2007–2013, Texas Instruments Incorporated 9 Evaluation Board Schematic 6 10 www.ti.com Evaluation Board Schematic AN-1617 LM25116 Evaluation Board SNVA232A – April 2007 – Revised April 2013 Submit Documentation Feedback Copyright © 2007–2013, Texas Instruments Incorporated IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. 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