LM2747EVAL

User's Guide SNVA150A – April 2006 – Revised May 2013 AN-1449 LM2747 Evaluation Board 1 Introduction This document describes the LM2747 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 LM2747 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 V to 6 V (VCC), the driver sections are designed to accept input supply rails (VIN) as high as 14 V. The demo board design regulates to an output voltage of 1.2 V at 3.5A with a switching frequency of 1MHz from a 1 MHz clock source that has an amplitude from 0 V to VCC. Note, the demo board is optimized for a 1MHz, 14 V input voltage compensation design with VCC = 3.3 V. If a slower switching frequency and input voltage is desired, please consult the device data sheet for control loop compensation procedures. For additional design modifications, see the Design Consideration section of the LM2747 Synchronous Buck Controller With Pre-Bias Startup, and Optional Clock Synchronization Data Sheet (SNVS370). The demo board accommodates the use of banana clips to clip onto pads on the board, if preferred, the pads inner diameters are 100mils, for which a solder terminal can be placed (Newark 40F6004). The PCB is designed on two layers with 1oz. copper on a 62mil FR4 laminate. 2 Additional Footprints An additional footprint D1 is available for a Schottky diode to be placed in parallel with 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 0.6 V 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 flush to the source of the low side MOSFET and drain of the high side MOSFET, in order to provide low supply impedance. For example, component C13 is used in combination with aluminum electrolytic input filter capacitors, placed in designators C12 and C14. If MLCCs are used in designators C12 and C14 component C13 is not necessary. All trademarks are the property of their respective owners. SNVA150A – April 2006 – Revised May 2013 Submit Documentation Feedback AN-1449 LM2747 Evaluation Board Copyright © 2006–2013, Texas Instruments Incorporated 1 Typical Application Circuit 3 www.ti.com Typical Application Circuit The typical application circuit in Figure 1 provides the component designators used on the demo board. VCC J1 LM2747 SD PWGD VCC HG BOO T ISEN FREQ/SYNC 0V Clock CCLK VIN C12 VCC C5 C10 R11 R8 R1 D2 R2 C7 C14 Q1 L1 R4 VOUT LG SS/TRACK PGND SGND PGND + Q2 C16 FB EAO C9 C8 R5 C11 R6 R3 R7 Figure 1. Typical Application 2 AN-1449 LM2747 Evaluation Board SNVA150A – April 2006 – Revised May 2013 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Performance Characteristics (Output Ripple Voltage and Switch Node Voltage) www.ti.com 4 Performance Characteristics (Output Ripple Voltage and Switch Node Voltage) Figure 2. VIN = VCC = 3.3 V, VOUT = 1.2 V, ILOAD = 0A, fSW = 1MHz 20 MHz Bandwidth Limit Figure 3. VIN = VCC = 3.3 V, VOUT = 1.2 V, ILOAD = 3.5A, fSW = 1MHz. 20 MHz Bandwidth Limit Figure 4. VIN = 14 V, VCC = 5 V, VOUT = 1.2 V, ILOAD = 0A, fSW = 1MHz. 20 MHz Bandwidth Limit Figure 5. VIN = 14 V, VCC = 5 V, VOUT = 1.2 V, ILOAD = 3.5A, fSW = 1MHz. 20 MHz Bandwidth Limit SNVA150A – April 2006 – Revised May 2013 Submit Documentation Feedback AN-1449 LM2747 Evaluation Board Copyright © 2006–2013, Texas Instruments Incorporated 3 Performance Characteristics (Output Ripple Voltage and Switch Node Voltage) VCC R1 D2 C10 C13 VCC J1 LM2747 SD PWGD VCC HG BOO T ISEN FREQ/SYNC 0V Clock CCLK VIN R11 R8 C5 www.ti.com R2 C7 C12 C14 Q1 L1 R4 VOUT LG SS/TRACK PGND SGND PGND D1 Q2 C15 + + C16 FB EAO C9 C8 R5 C11 R6 R3 R7 Figure 6. Complete Demo Board Schematic Table 1. Bill of Materials (BOM) 4 Designator Function Part Description Part Number U1 Controller LM2747 TSSOP14 Texas Instruments C5 VCC Decoupling Cer Cap 1 µF 25 V 10% 0805 Murata GRM216R61E105KA12B C7 Soft Start Cap Cer Cap 12 nF 25 V 10% 0805 Vishay VJ0805Y123KXX C8 Comp Cap Cer Cap 1.5 nF 25 V 10% 0805 Vishay VJ0805Y152KXX C9 Comp Cap Cer Cap 18 pF 25 V 10% 0805 Vishay VJ0805A180KAA C10 Cboot Cer Cap 0.1 µF 25 V 10% 0805 Vishay VJ0805Y104KXX C11 Comp Cap Cer Cap 1.8 nF 25 V 10% 0805 Vishay VJ0805Y182KXX C12 Input Filter Cap Cer Cap 10 µF 25 V 10% 1210 AVX 12103D106MAT AVX 12103D106MAT C14 Input Filter Cap Cer Cap 10 µF 25 V 10% 1210 C15 Output Filter Cap 470µF, 6.3 V, 10 mΩ ESR POScap Sanyo 6TPD470 R1 Filter Resistor Res 10 Ω .25W 0805 Vishay CRCW08051000F R2 Frequency Adjust Res Res18.7 kΩ .25W 0805 Vishay CRCW08052187F R3 Comp Res Res 17.4 kΩ .25W 0805 Vishay CRCW08051742F R4 Current Limit Res Res 3.16 kΩ .25W 0805 Vishay CRCW08053161F R5 Comp Res Res 2.94 kΩ .25W 0805 Vishay CRCW08052941F R6 Res Divider, upper Res 10.0 kΩ .25W 0805 Vishay CRCW08051002F R7 Res Divider, lower Res 10.0 kΩ .25W 0805 Vishay CRCW08051002F R8 PWGD Pull-Up Res 100 kΩ .25W 0805 Vishay CRCW08051003F R11 Shut Down Pull-Up Res 100 kΩ .25W 0805 Vishay CRCW080561003F D2 Bootstrap Diode Schottky Diode, SOD-123 MBR0530LTI L1 Output Filter Inductor Inductor 1 µH, 5.3Arms, 10.2 mΩ Cooper DR73-1R0 Q1-Q2 Top and Bottom FETs Dual N-MOSFET, VDS = 20 V, 24 mΩ @ 2.5 V Vishay 9926BDY CCLK Sync AC Coupling Cap Cer Cap 56 pF 25 V 10% 0805 Vishay VJ0805A560KXAA AN-1449 LM2747 Evaluation Board SNVA150A – April 2006 – Revised May 2013 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated PCB Layout Diagrams www.ti.com 5 PCB Layout Diagrams Figure 7. Top Layer and Top Overlay Figure 8. Bottom Layer SNVA150A – April 2006 – Revised May 2013 Submit Documentation Feedback AN-1449 LM2747 Evaluation Board Copyright © 2006–2013, 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. All semiconductor products (also referred to herein as “components”) are sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment. 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