LM3475EVAL

www.ti.com Table of Contents User’s Guide AN-1381 LM3475 Evaluation Board Table of Contents 1 Introduction.............................................................................................................................................................................2 2 Setting Vout............................................................................................................................................................................. 2 3 Optional Components............................................................................................................................................................ 2 4 PCB Layout Diagrams............................................................................................................................................................ 4 Trademarks All trademarks are the property of their respective owners. SNVA115B – MAY 2005 – REVISED FEBRUARY 2022 Submit Document Feedback AN-1381 LM3475 Evaluation Board Copyright © 2022 Texas Instruments Incorporated 1 Introduction www.ti.com 1 Introduction The LM3475 evaluation board is provided as a tool for developing DC/DC converters based on the LM3475 IC. As shown in Figure 3-1, the evaluation board is configured to provide an output of 2.5 V at up to 2 A from an input up to 10 V. The corresponding bill of material is given in Table 3-1. Typical efficiencies are shown in Figure 3-2 and Figure 3-3. Figure 4-1 and Figure 4-2 show the board layout. To aid in the design and evaluation of DC/DC buck converters based on the LM3475 controller, the LM3475 evaluation board can be easily re-configured for different output voltages. 2 Setting Vout Vout can be set using RFB1, as shown in Equation 1: VOUT = VFB x (RFB1 + RFB2) / RFB2 (1) where • VFB is 0.8 V typically. See the device-specific data sheet before changing any component values since additional design adjustments can be required. 3 Optional Components A feedforward capacitor, CFF, is placed on the board, which will increase operating frequency. However, the speed up effect decreases with lower output voltage and is negligible below 1.6-V output. A 0 Ω is used to pull up the EN pin for always on operation. The enable pin can be pulled low at the EN post to shutdown the device. If this resistor is removed, any analog level signal can be used to enable and disable the device. L1 10 PH Q1 Si2343 VIN = 5V VOUT = 2.5V/2A COUT CIN 10 PF D1 5 PGATE 4 VIN GND 2 CFF 1 nF LM3475 3 EN FB 100 PF RFB1 2.15k 1 RFB2 1k Figure 3-1. Full Demo Board Schematic 2 AN-1381 LM3475 Evaluation Board SNVA115B – MAY 2005 – REVISED FEBRUARY 2022 Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated www.ti.com Optional Components 98 EFFICIENCY (%) 96 94 92 90 88 86 84 1 0.5 1.5 2 OUTPUT CURRENT (A) Figure 3-2. Efficiency vs Output Current (VIN = 5 V) 100 EFFICIENCY (%) 80 60 40 20 0 4 5 6 7 8 9 10 INPUT VOLTAGE (VIN) Figure 3-3. Efficiency vs Input Voltage (Iout = 2 A) Table 3-1. Bill of Materials (BOM) Designator Part Description Part Number CIN 10 µF, 16-V ceramic Yuden EMK325BJ106MN COUT 100 µF, 6-V tantalum AVX TPSY107M006R0100 CFF 1 nF, 25-V ceramic VJ1206Y102KXXA D1 Schottky 20 V, 2 A Central CMSH2-20L L1 10 µH, 3.1 A Sumida CDRH103R100 Q1 Si 2343 30 V, 2.5 A Vishay Si2343 RFB2 1 kΩ Vishay CRCW08051001F RFB1 2.15 kΩ Vishay CRCW08052151F R2 0Ω Vishay CRCW08050R00F SNVA115B – MAY 2005 – REVISED FEBRUARY 2022 Submit Document Feedback AN-1381 LM3475 Evaluation Board Copyright © 2022 Texas Instruments Incorporated 3 PCB Layout Diagrams www.ti.com Cin GN D Q1 D1 Cout 4 PCB Layout Diagrams RFB2 RFB1 L 1 Vou t CFF 0 Ohm EN Vin Figure 4-1. Top Side Layout Figure 4-2. Bottom Side Layout 4 AN-1381 LM3475 Evaluation Board SNVA115B – MAY 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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