LM2743EVAL/NOPB

User's Guide SNVA102A – October 2005 – Revised April 2013 AN —1356 LM2743 Evaluation Board 1 Introduction This application notes describes the LM2743 printed circuit board (PCB) design and provides an example typical application circuit. The demo board allows component design flexibility in order to demonstrate the versatility of the LM2743 IC. The demo board contains a voltage-mode, high-speed synchronous buck regulator controller. Though the control sections of the IC are rated for 3 to 6V (VCC), the driver sections are designed to accept input supply rails (VIN) as high as 14V. The demo board design regulates to an output voltage of 1.2V at 3.5A with a switching frequency of 1MHz. Note, the demo board is optimized for a 1MHz, 14V input voltage compensation design, if another switching frequency and input voltage is desired, please consult the LM2743 data sheet for control loop compensation procedures. For additional design modifications refer to the Design Consideration section of the LM2743 Low Voltage N-Channel MOSFET Synchronous Buck Regulator Controller Data Sheet (SNVS276). The PCB is designed on two layers with 1oz. copper on a 62mil FR4 laminate. 2 Additional Footprints A Schottky diode footprint (D1) is available in parallel to the low side MOSFET. This component can improve efficiency, due to the lower forward drop than the low side MOSFET body diode conducting during the anti-shoot through period. Select a Schottky diode that maintains a forward drop around 0.4 to 0.6V at the maximum load current (consult the I-V curve). In addition select the reverse breakdown voltage to have sufficient margin above the maximum input voltage. Footprint C13 is available for a multilayer ceramic capacitor (MLCC) connected as close as possible to the source of the low side MOSFET and drain of the high side MOSFET. This will provide low supply impedance to the high speed switch currents, thus minimizing the input supply noise. For example; a MLCC is used (C13) in combination with aluminum electrolytic input filter capacitors, placed in designators C12 and C14, because MLCC have lower impedance than electrolytics. If MLCCs are used in designators C12 and C14 then component C13 is not necessary. 3 Typical Application Circuit The typical application circuit in Figure 1 provides the component designators used on the demo board. All trademarks are the property of their respective owners. SNVA102A – October 2005 – Revised April 2013 Submit Documentation Feedback AN —1356 LM2743 Evaluation Board Copyright © 2005–2013, Texas Instruments Incorporated 1 Typical Application Circuit www.ti.com VC D2 C R11 R8 R1 J1 C5 C12 HG VCC SD BOOT PWGD C14 Q1 VOUT L1 R4 ISEN LM2743 FREQ R2 C7 VIN C10 LG SS/TRACK PGND SGND PGND + Q2 C16 FB EAO C9 R3 R5 C11 R6 C8 R7 Figure 1. Typical Application 2 AN —1356 LM2743 Evaluation Board SNVA102A – October 2005 – Revised April 2013 Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Performance Characteristics www.ti.com 4 Performance Characteristics 4.1 Switch Node Voltage and Output Ripple Voltage Figure 2. VIN = VCC = 3.3V, VOUT = 1.2V, ILOAD = 0A, fSW = 1MHz. 20 MHz Bandwidth Limit Figure 3. VIN = VCC = 3.3V, VOUT = 1.2V, ILOAD = 3.5A, fSW = 1MHz. 20 MHz Bandwidth Limit Figure 4. VIN = 14V, VCC = 5V, VOUT = 1.2V, ILOAD = 0A, fSW = 1MHz. 20 MHz Bandwidth Limit Figure 5. VIN = 14V, VCC = 5V, VOUT = 1.2V, ILOAD = 3.5A, fSW = 1MHz. 20 MHz Bandwidth Limit SNVA102A – October 2005 – Revised April 2013 Submit Documentation Feedback AN —1356 LM2743 Evaluation Board Copyright © 2005–2013, Texas Instruments Incorporated 3 Performance Characteristics www.ti.com Table 1. Bill of Materials Designator Function Part Description Part Number U1 Controller IC LM2743 TSSOP14 Texas Instruments C5 VCC Decoupling Cer Cap 1µF 25V 10% 0805 Murata GRM216R61E105KA12B C7 Soft Start Cap Cer Cap 12nF 25V 10% 0805 Vishay VJ0805Y123KXX C8 Comp Cap Cer Cap 1.5nF 25V 10% 0805 Vishay VJ0805Y152KXX C9 Comp Cap Cer Cap 18pF 25V 10% 0805 Vishay VJ0805A180KAA C10 Cboot Cer Cap 0.1µF 25V 10% 0805 Vishay VJ0805Y104KXX C11 Comp Cap Cer Cap 1.8nF 25V 10% 0805 Vishay VJ0805Y182KXX C12 Input Filter Cap Cer Cap 10uF 25V 10% 1210 AVX 12103D106MAT C14 Input Filter Cap Cer Cap 10uF 25V 10% 1210 AVX 12103D106MAT C15 Output Filter Cap 470µF, 6.3V, 10mΩ ESR POScap Sanyo 6TPD470 R1 Filter Resistor Res 10Ω .25W 0805 Vishay CRCW08051000F R2 Frequency Adjust Res Res 24.9KΩ .25W 0805 Vishay CRCW08052492F R3 Comp Res Res 17.4KΩ .25W 0805 Vishay CRCW08051742F R4 Current Limit Res Res 3.16KΩ .25W 0805 Vishay CRCW08053161F R5 Comp Res Res 2.94KΩ .25W 0805 Vishay CRCW08052941F R6 Res Divider, upper Res 10.0KΩ .25W 0805 Vishay CRCW08051002F R7 Res Divider, lower Res 10.0KΩ .25W 0805 Vishay CRCW08051002F R8 PWGD Pull-Up Res 100KΩ .25W 0805 Vishay CRCW08051003F R11 Shut Down Pull-Up Res 100KΩ .25W 0805 Vishay CRCW080561003F D2 Bootstrap Diode Schottky Diode, SOD-123 MBR0530LTI L1 Output Filter Inductor Inductor 1µH, 5.3Arms, 10.2mΩ Cooper DR73-1R0 Q1-Q2 Top and Bottom FETs Dual N-MOSFET, VDS = 20V, 24mΩ @ 2.5V Vishay 9926BDY VC D2 C R1 R11 R8 C13 VCC J1 C5 HG SD BOOT PWGD FREQ R2 C7 VIN C10 C12 C14 Q1 VOUT L1 R4 ISEN LM2743 LG SS/TRACK PGND SGND PGND D1 Q2 C15 + + C16 FB EAO C9 R3 R5 C11 R6 C8 R7 Figure 6. Complete Demo Board Schematic 4 AN —1356 LM2743 Evaluation Board SNVA102A – October 2005 – Revised April 2013 Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated PCB Layout Diagram(s) www.ti.com 5 PCB Layout Diagram(s) Figure 7. Top Layer and Top Overlay Figure 8. Bottom Layer SNVA102A – October 2005 – Revised April 2013 Submit Documentation Feedback AN —1356 LM2743 Evaluation Board Copyright © 2005–2013, Texas Instruments Incorporated 5 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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