LM2744EVAL

www.ti.com Table of Contents User’s Guide LM2744 Buck Controller Evaluation Module User's Guide Table of Contents 1 Introduction.............................................................................................................................................................................2 2 Additional Footprints..............................................................................................................................................................3 3 Guidelines for Additional Options.........................................................................................................................................4 4 Typical Application Circuit.....................................................................................................................................................5 5 Performance Characteristics.................................................................................................................................................6 5.1 Load Transient Response.................................................................................................................................................. 6 5.2 Switch Node Voltage and Output Ripple Voltage............................................................................................................... 6 6 PCB Layout Diagrams............................................................................................................................................................ 8 7 Revision History......................................................................................................................................................................8 Trademarks All trademarks are the property of their respective owners. SNVA103B – OCTOBER 2005 – REVISED FEBRUARY 2022 LM2744 Buck Controller Evaluation Module User's Guide Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated 1 Introduction www.ti.com 1 Introduction This user's guide 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 LM2744 IC. The demo board contains a voltage-mode, high-speed synchronous buck regulator controller with an external adjustable reference voltage between 0.5 V and 1.5 V. The demo board design incorporates the LM4140 high precision low noise reference IC providing 1.0 V to the reference pin (VREF). Though the control sections of the IC are rated for 3 to 6 V (VCC), the driver sections are designed to accept input supply rails (VIN) as high as 14 V. It operates at a fixed frequency, adjustable from 50 kHz to 1 MHz with one external resistor. The demo board design regulates to an output voltage of 1.2 V at 3.5 A with a switching frequency of 1 MHz. Note, the demo board is optimized for a 1-MHz, 14-V input voltage compensation design. If another switching frequency and input voltage is desired, please consult the LM2744 Low Voltage N-Chan MOSFET Synch Buck Regr Cntrl w/ Ext Ref data sheet for control loop compensation procedures. For additional design modifications, refer to the Design Consideration section of the LM2744 Low Voltage N-Chan MOSFET Synch Buck Regr Cntrl w/ Ext Ref data sheet. 2 LM2744 Buck Controller Evaluation Module User's Guide SNVA103B – OCTOBER 2005 – REVISED FEBRUARY 2022 Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated www.ti.com Additional Footprints 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 antishoot–through period. Select a Schottky diode that maintains a forward drop around 0.4 V 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 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 has lower impedance than electrolytics. If MLCCs are used in designators C12 and C14, component C13 is not necessary. The PCB is designed on two layers with 1-oz. copper on a 62-mil FR4 laminate. SNVA103B – OCTOBER 2005 – REVISED FEBRUARY 2022 LM2744 Buck Controller Evaluation Module User's Guide Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated 3 Guidelines for Additional Options www.ti.com 3 Guidelines for Additional Options When using a DC power supply to set a reference voltage (VREF), connect a capacitor (C20) from VDCS to GND to filter the DC power supply. A good starting point is 10 µF, but it may need to be varied depending on the magnitude of the DC power supply noise (any make of capacitor will do as long as the capacitance is maintained within the operating temperature range). Remove R10 and place a 0-Ω jumper in designator R12. Designators R12 and R13 are provided for DDR SDRAM (double data rate synchronous dynamic random access memory) active termination design. Set VREF to half the DDR supply voltage by using designators R12 and R13 as a voltage divider. Remove resistors R7 and R10 and capacitor C21, and connect the DDR supply voltage rail to terminal VDCS. Refer to Figure 4-2. The modified circuit in Figure 4-1 can sink or source current in excess of 3 A. A load transient response applied to the output of Figure 4-2 is provided in Figure 5-1. Do not exceed 5.6 V on the VCC pin of the demo board. The board layout connects both the input voltage of the LM4140-1.0 (pin 2) and the control section of the LM2744 (VCC). The maximum DC supply voltage for the control section of the LM2744 is 6 V, while 5.6 V is the maximum rating for any input pin of the LM4140. If the design requires the control section of the LM2744 to be 6 V, a shunt zener reference can be placed at designator location (D3) to maintain the input voltage of the LM4140 between 1.8 V and 5.5 V. The cathode of the zener is connected to the input of the LM4140 and the anode to GND. The resistance of R10 must be selected to supply the appropriate amount of biasing current into the zener and the LM4140 (refer to the Electrical Characteristics table of the LM2744 Low Voltage N-Chan MOSFET Synch Buck Regr Cntrl w/ Ext Ref data sheet. 4 LM2744 Buck Controller Evaluation Module User's Guide SNVA103B – OCTOBER 2005 – REVISED FEBRUARY 2022 Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated www.ti.com Typical Application Circuit 4 Typical Application Circuit The typical application circuit in Figure 4-1 provides the component designators used on the demo board. VC D2 C VIN C10 R11 R1 C12 VCC J1 C5 HG SD BOOT PWGD FREQ R10 R2 C7 C22 EN Q1 VOUT L1 R4 ISEN LM2744 LG SS/TRACK SGND VREF PGND + Q2 C16 FB EAO VEN C14 R8 C9 VREF R5 LM4140 -1.0 C11 R6 C8 R3 C21 R7 PGND NC Figure 4-1. Typical Application VC D2 C C12 VCC J1 C5 HG BOO T ISEN SD PWGD FREQ R2 C7 R12 VDCS + C20 VIN R11 R8 R1 C10 LM2744 C14 Q1 VOUT L1 R4 LG SS/TRACK SGND VREF PGND + Q2 C16 FB EAO C21/ R13 C9 R5 R3 C11 R6 C8 Figure 4-2. DDR SDRAM Termination Supply SNVA103B – OCTOBER 2005 – REVISED FEBRUARY 2022 LM2744 Buck Controller Evaluation Module User's Guide Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated 5 Performance Characteristics www.ti.com 5 Performance Characteristics 5.1 Load Transient Response Figure 5-1. ±3-A Load Transient Response Applied to the Circuit in Figure 4-2 (VIN = VCC = 3.3 V and VOUT = 1.2 V). CH 2 - VOUT AC Coupled and CH 3 - 5 A/DIV Figure 5-2. Efficiency vs. Load Current VOUT = 1.2 V, fSW = 1 MHz 5.2 Switch Node Voltage and Output Ripple Voltage Figure 5-3. VIN = VCC = 3.3 V, VOUT = 1.2 V, ILOAD = 0 A, fSW = 1 MHz, 20-MHz Bandwidth Limit Figure 5-4. VIN = VCC = 3.3 V, VOUT = 1.2 V, ILOAD = 3.5 A, fSW = 1 MHz, 20-MHz Bandwidth Limit Figure 5-5. VIN = 14 V, VCC = 5 V, VOUT = 1.2 V, ILOAD = 0 A, fSW = 1 MHz, 20-MHz Bandwidth Limit Figure 5-6. VIN = 14 V, VCC = 5 V, VOUT = 1.2 V, ILOAD = 3.5 A, fSW = 1 MHz, 20-MHz Bandwidth Limit Table 5-1. Bill of Materials Designator 6 Function Part Description Part Number U1 Controller IC LM2744 TSSOP14 Texas Instruments U2 Low Dropout Reg IC LM4140BCM-1.0 SOIC-8 Texas Instruments C5 VCC Decoupling Ceramic Capacitor, 1 µF, 25 V, 10%, 0805 Murata GRM216R61E105KA12B C7 Soft Start Cap Ceramic Capacitor, 12 nF, 25 V, 10%, 0805 Vishay VJ0805Y123KXX LM2744 Buck Controller Evaluation Module User's Guide SNVA103B – OCTOBER 2005 – REVISED FEBRUARY 2022 Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated www.ti.com Performance Characteristics Table 5-1. Bill of Materials (continued) Designator Function Part Description Part Number C8 Comp Cap Ceramic Capacitor, 1.2 nF, 25 V, 10%, 0805 Vishay VJ0805Y122KXX C9 Comp Cap Ceramic Capacitor, 15 pF, 50 V, 10%, 0805 Vishay VJ0805A150KAA C10 Cboot Ceramic Capacitor, 0.1 µF, 25 V, 10%, 0805 Vishay VJ0805Y104KXX C11 Comp Cap Ceramic Capacitor, 1.8 nF, 25 V, 10%, 0805 Vishay VJ0805Y182KXX C12 Input Filter Cap Ceramic Capacitor, 10 μF, 25 V, 10%, 1210 AVX 12103D106MAT C14 Input Filter Cap Ceramic Capacitor, 10 μF, 25 V, 10%, 1210 AVX 12103D106MAT C16 Output Filter Cap 470 μF, 6.3 V, 10-mΩ ESR POScap Sanyo 6TPD470 C21 Reference Output Cap Niobium Oxide Capacitor, 4.7 µF, 6 V AVX NOJA475M0006R C22 Reference Input Cap Ceramic Capacitor, 0.47 µF, 25 V, 10%, 1206 Vishay VJ1206Y474KXX R1 VCC Filter Resistor Resistor 10 Ω, .25 W, 0805 Vishay CRCW08051000F R2 Frequency Adjust Resistor Resistor, 24.9 kΩ, .25 W, 0805 Vishay CRCW08052492F R3 Comp Resistor Resistor, 21 kΩ, .25 W, 0805 Vishay CRCW08052102F R4 Current Limit Resistor Resistor, 3.16 kΩ, .25 W, 0805 Vishay CRCW08053161F R5 Comp Resistor Resistor, 2.94 kΩ, .25 W, 0805 Vishay CRCW08052941F R6 Resistor Divider, upper Resistor, 10.0 kΩ, .25 W, 0805 Vishay CRCW08051002F R7 Resistor Divider, lower Resistor, 59 kΩ, .25 W, 0805 Vishay CRCW08055902F R8 PWGD Pull-Up Resistor, 100 kΩ, .25 W, 0805 Vishay CRCW08051003F R10 Zero Ohm Resistor, 0 Ω, 0805 Vishay CRCW08050000 R11 Shut Down Pull-Up Resistor, 100 kΩ, .25 W, 0805 Vishay CRCW12061003F D2 Bootstrap Diode Schottky Diode, SOD-123 MBR0530LTI L1 Output Filter Inductor Inductor 1 µH, 5.3 Arms, 10.2 mΩ Cooper DR73-1R0 Q1-Q2 Top and Bottom FETs Dual N-MOSFET, VDS = 20 V, 24 mΩ at 2.5 V Vishay 9926BDY V CC V D2 R 11 R8 C 13 C 12 C 14 V CC HG J1 C5 IN C 10 SD BO O T IS E N Q 1 V L1 R4 O UT PW G D FR EQ LM 2744 LG R2 R 10 V C7 REF S S /T R A C K SG N D VR EF PG N D D3 C 22 EN REF LM 4140 -1 .0 PG N D C 15 + + C 16 C9 R9 V D1 FB EAO V IN Q 2 R5 R3 C 11 R6 C8 C 21 R7 NC Figure 5-7. Complete Demo Board Schematic SNVA103B – OCTOBER 2005 – REVISED FEBRUARY 2022 LM2744 Buck Controller Evaluation Module User's Guide Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated 7 PCB Layout Diagrams www.ti.com 6 PCB Layout Diagrams Figure 6-1. Top Layer and Top Overlay Figure 6-2. Bottom Layer 7 Revision History NOTE: Page numbers for previous revisions may differ from page numbers in the current version. Changes from Revision A (April 2013) to Revision B (February 2022) 8 LM2744 Buck Controller Evaluation Module User's Guide Page SNVA103B – OCTOBER 2005 – REVISED FEBRUARY 2022 Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated IMPORTANT NOTICE AND DISCLAIMER TI PROVIDES TECHNICAL AND RELIABILITY DATA (INCLUDING DATA SHEETS), DESIGN RESOURCES (INCLUDING REFERENCE DESIGNS), APPLICATION OR OTHER DESIGN ADVICE, WEB TOOLS, SAFETY INFORMATION, AND OTHER RESOURCES “AS IS” AND WITH ALL FAULTS, AND DISCLAIMS ALL WARRANTIES, EXPRESS AND IMPLIED, INCLUDING WITHOUT LIMITATION ANY IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT OF THIRD PARTY INTELLECTUAL PROPERTY RIGHTS. These resources are intended for skilled developers designing with TI products. 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