LM3743-1000EVAL

User's Guide SNVA151A – September 2006 – Revised May 2013 AN-1450 LM3743 Evaluation Board 1 Introduction The LM3743 is a voltage mode PWM buck controller that implements synchronous rectification. It provides a low cost, fault tolerant, and efficient point of load solution. To reduce component count several parameters are fixed, such as switching frequency and the short circuit protection level. In steady state operation the LM3743 is always synchronous, even at no load, thus simplifying the compensation design. The LM3743 ensures a smooth and controlled start-up when the output is pre-biased. Two levels of current limit protection enhance the robustness of the power supply and requires no current sense resistor in the power path. The primary level of protection is the low side current limit and is achieved by sensing the voltage VDS across the low side MOSFET. The second level of protection is the high side current limit, which protects power components from extremely high currents caused by switch node short-circuit to ground. 2 Specifics Of The Board The input voltage to the power components (VIN) and the input voltage on the control section (VCC) must be in the range of 3.0V to 5.5V. The 300 kHz demo board design regulates to an output voltage of 1.2V and up to 13A. The 1 MHz demo board design regulates to an output voltage of 1.5V and up to 9A. For additional design modifications, see the Design Consideration section of the LM3743 High-Performance Synchronous Buck Controller with Comprehensive Fault Protection Features Data Sheet (SNVS427). The PCB is designed on four layers, the top and bottom layers are 2oz. copper and the two inner layers are 1oz. copper. The board measures 2.4 in. x 1.36 in. (6.1 cm x 3.44 cm) and is 62mil (.062”) thick on a FR4 laminate. 3 Additional Footprints When the tracking feature of the LM3743 is used, remove the soft-start capacitor C4 and use a resistor divider on designators R7 and C4. The ground and track post have been provided for your connecting convenience. 4 MOSFET Footprints The LM3743 demo board accommodates footprints for single N-MOSFETs with standard SOIC-8 packages and with exposed drain pads. The MOSFET footprint has the pinout as shown in Figure 1. Some examples of MOSFET packages with exposed drain pads are also illustrated. All trademarks are the property of their respective owners. SNVA151A – September 2006 – Revised May 2013 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated AN-1450 LM3743 Evaluation Board 1 Performance Characteristics www.ti.com S D S D SO-8 S D G D S D S D S D G D S D S D S D G D Figure 1. SOIC-8 Footprint 5 Performance Characteristics Efficiency Figure 2. Efficiency vs. Load Current VOUT = 1.2V, fSW = 300 kHz Figure 3. Efficiency vs. Load Current VOUT = 1.5V, fSW = 1MHz Switch Node Voltage and Output Voltage Ripple 2 AN-1450 LM3743 Evaluation Board SNVA151A – September 2006 – Revised May 2013 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Performance Characteristics www.ti.com 20 mV/DIV 20 mV/DIV 2V/DIV 2V/DIV 200 ns/DIV 200 ns/DIV Figure 4. VIN = 5V, VOUT = 1.5V, ILOAD = 0A, fSW = 1MHz 20 MHz Bandwidth Limit Figure 5. VIN = 5V, VOUT = 1.5V, ILOAD = 9A, fSW = 1MHz 20 MHz Bandwidth Limit 20 mV/DIV 20 mV/DIV 2V/DIV 2V/DIV 1 Ps/DIV 1 Ps/DIV Figure 6. VIN = 5V, VOUT = 1.2V, ILOAD = 0A, fSW = 300kHz 20 MHz Bandwidth Limit Figure 7. VIN = 5V, VOUT = 1.2V, ILOAD = 13A, fSW = 300kHz 20 MHz Bandwidth Limit SNVA151A – September 2006 – Revised May 2013 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated AN-1450 LM3743 Evaluation Board 3 Performance Characteristics www.ti.com Table 1. 300 kHz Bill of Materials (BOM) Designator Function Description Part Number Vendor U1 Controller Buck Controller LM3743 Texas Instruments C1 Input Filter 22 µF,10 V, X7R, 1812 GRM43ER71A226KE01B Murata C2 Input Filter Al-elec, 10 V, 470 µF 10ME470WX Sanyo C3 Decoupling 1 µF, 10 V, X7R, 0805 0805ZC105KAT AVX C4 Soft Start Cap 180 nF, 25 V, X7R VJ0805Y184KXXA Vishay C5 Output Filter 470 µF, 4 V, 15mΩ 4TPE470MFL Sanyo C6 Output Filter 10 µF, 6.3 V, 0805 0805D106MAT AVX C7 Comp Cap 56 pF, 25 V, 0805 VJ0805A560KXAA Vishay C8 Comp Cap 2.2 nF, 25 V, 0805 VJ0805A222KXAA Vishay C9 Comp Cap 1.5 nF, 25 V, 0805 VJ0805Y152KXXA Vishay C10 Bootstrap Cap .47 µF, 25 V, 0805 VJ0805Y474KXXA Vishay R1 Current Limit Res 1.78 kΩ, 0805 CRCW08051781F Vishay R2 Top FB Resistor 10 kΩ, 0805 CRCW08051002F Vishay R3 Bottom FB Resistor 20 kΩ, 0805 CRCW08052002F Vishay R4 Comp Resistor 22.6 kΩ, 0805 CRCW08052262F Vishay R5 Comp Resistor 3.57 kΩ, 0805 CRCW08053571F Vishay R6 VCC Filter Resistor 2 Ω, 0805 CRCW08052R00F Vishay L1 Output Filter 1.5 µH, 13.8A, 2.9 mΩ DR125-1R5 Cooper D1 Bootstrap Diode 500 mA, 20 V, VF =.3 V MBR0520LT1 Onsemi Q1 Top FET 4.5 mΩ @VGS = 4.5 V, 21 nC Si7882DP Vishay Q2 Bottom FET 4.5 mΩ @VGS = 4.5 V, 21 nC Si7882DP Vishay VIN = 3 to 5.5V D1 R6 BOOT C10 VCC HGATE C3 C1 Q1 + + C2 SW LM3743 L1 R1 Vo = 1.2V, 13A ILIM R7 SS/TRACK TRACK GND LGATE C4 Q2 + C5 + C6 GND COMP/EN FB R2 R5 C8 C7 C9 R4 R3 Figure 8. 300 kHz Demo Board Schematic 4 AN-1450 LM3743 Evaluation Board SNVA151A – September 2006 – Revised May 2013 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Performance Characteristics www.ti.com Table 2. 1 MHz Bill of Materials Designator Function Description Part Number Vendor U1 Controller Buck Controller LM3743 Texas Instruments C1 Input Filter 22 µF, 10 V, X7R, 1812 GRM43ER71A226KE01B Murata Sanyo C2 Input Filter Al-elec, 10 V, 470 µF 10ME470WX C3 Decoupling 1 µF, 10 V, X7R, 0805 0805ZC105KAT AVX C4 Soft Start Cap 180 nF, 25 V, X7R VJ0805Y184KXXA Vishay C5 Output Filter 470 µF, 4 V, 15mΩ 4TPE470MFL Sanyo C6 Output Filter 10 µF, 6.3 V, 0805 0805D106MAT AVX C7 Comp Cap 8.2 pF, 25 V, 0805 VJ0805A8R2KXAA Vishay C8 Comp Cap 820 pF, 25 V, 0805 VJ0805A821KXAA Vishay C9 Comp Cap 470 pF, 25 V, 0805 VJ0805Y471KXXA Vishay C10 Bootstrap Cap .1 µF, 25 V, 0805 VJ0805Y104KXXA Vishay R1 Current Limit Res 1.1 kΩ, 0805 CRCW08051101F Vishay R2 Top FB Resistor 10 kΩ, 0805 CRCW08051002F Vishay R3 Bottom FB Resistor 11.3 kΩ, 0805 CRCW08057871F Vishay R4 Comp Resistor 35.7 kΩ, 0805 CRCW08053572F Vishay R5 Comp Resistor 8.87 kΩ, 0805 CRCW08058871F Vishay R6 VCC Filter Resistor 2 Ω, 0805 CRCW08052R00F Vishay L1 Output Filter .47 µH, 11.6A, 3.6 mΩ FP3-R47 Cooper D1 Bootstrap Diode 500 mA, 20 V, VF =.3 V MBR0520LT1 Onsemi Q1 Top FET 4.5 mΩ @ VGS = 4.5 V, 21 nC Si7882DP Vishay Q2 Bottom FET 4.5 mΩ @ VGS = 4.5 V, 21 nC Si7882DP Vishay VIN = 3 to 5.5V D1 R6 BOOT C10 VCC HGATE C3 C1 Q1 + + C2 SW LM3743 R1 Vo = 1.5V, 9A L1 ILIM R7 SS/TRACK TRACK GND LGATE C4 Q2 + C5 + C6 GND COMP/EN FB R2 R5 C8 C7 C9 R4 R3 Figure 9. 1 MHz Demo Board Schematic SNVA151A – September 2006 – Revised May 2013 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated AN-1450 LM3743 Evaluation Board 5 PCB Layout Diagram(s) 6 www.ti.com PCB Layout Diagram(s) Figure 10. Top Layer Figure 11. Internal Layer I (Ground) 6 AN-1450 LM3743 Evaluation Board SNVA151A – September 2006 – Revised May 2013 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated PCB Layout Diagram(s) www.ti.com Figure 12. Internal Layer II (VIN and VOUT) Heat Sinking Layer Figure 13. Bottom Layer Heat Sinking Layer and Signal Traces SNVA151A – September 2006 – Revised May 2013 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated AN-1450 LM3743 Evaluation Board 7 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. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. 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