LM2698EVAL

User's Guide SNVA040C – September 2001 – Revised April 2013 AN-1202 LM2698 Demo Board 1 Introduction A printed circuit board (PCB) has been developed to aid in the design and evaluation of the LM2698 DCDC boost converter. This document contains information about the board. 2 General Description The LM2698 is a general purpose, high frequency DC-DC converter. This board is intended to demonstrate the primary advantages of the LM2698. The LM2698 is able to operate at 1.25 MHz switching frequency, yielding extremely high power density. The low RDS(ON) internal MOSFET allows for high conversion efficiency. It uses a current mode control scheme, giving superior line and load regulation. The LM2698 is a Simple Switcher®, which includes Switchers Made Simple software for fast, effective designs. The LM2698 demo board operates with the following parameters: 4.5 V ≤ VIN ≤ 9 V VOUT = 12 V 0 ≤ IOUT ≤ 400 mA (for IOUT vs VIN, see Figure 2) Simple Switcher is a registered trademark of Texas Instruments. All other trademarks are the property of their respective owners. SNVA040C – September 2001 – Revised April 2013 Submit Documentation Feedback Copyright © 2001–2013, Texas Instruments Incorporated AN-1202 LM2698 Demo Board 1 General Description www.ti.com (1) The inductance affects the stability of the converter. For tips on optimizing the inductance value, especially for input voltages less than 5 V, see the compensation section in the device-specific data sheet. To operate this demo board at voltages below 4.5 V with the supplied 10 µH inductor and remain in a safe stability region, use a 1.25 MHz switching frequency (if VIN > 5 V, a 600 kHz or 1.25 MHz switching frequency is acceptable). (2) When operating the LM2698 at 1.25 MHz switching frequency, it is recommended to increase the bypass capacitance, CBYP, to 0.220 µF. Figure 1. LM2698 Demo Board Schematic 2 AN-1202 LM2698 Demo Board SNVA040C – September 2001 – Revised April 2013 Submit Documentation Feedback Copyright © 2001–2013, Texas Instruments Incorporated Maximum Output Current www.ti.com Table 1. Bill of Materials (BOM) Component Value Description Model Number COUT 10 µF Output Capacitor TMK432BJ106MM (Taiyo Yuden) CIN 22 µF Input Capacitor LMK432BJ226MM (Taiyo Yuden) CC 4.7nF Compensation Capacitor VJ0805Y472MXAAT (Vishay) CBYP 0.1 µF Bypass Capacitor VJ0805Y104KXAAT (Vishay) D 1A, 20 V Schottky Power Diode MBRM120LT3 (ON-Semiconductor) L 10 µH Power Inductor CDRH6D38-100 (Sumida) RC 24.9k Compensation Resistor CRCW 0805 2492 FRT1 (Vishay) RFB1 30.1k Top Feedback Resistor CRCW 0805 3012 FRT1 (Vishay) RFB2 3.48k Bottom Feedback Resistor CRCW 0805 3481 FRT1 (Vishay) Table 2. Jumper Settings Jumper Setting J1 600 kHz 1.25 MHz J2 3 Description 600 kHz switching frequency 1.25 MHz switching frequency Run LM2698 is regulating SD LM2698 is shutdown Maximum Output Current The current limit of the LM2698 is with respect to the switch current. This means that the maximum output current to the load is dependent on duty cycle. With a fixed VOUT, the maximum output current will be a function of VIN, as shown in Figure 2. Figure 2. Maximum Output Current vs Input Voltage SNVA040C – September 2001 – Revised April 2013 Submit Documentation Feedback Copyright © 2001–2013, Texas Instruments Incorporated AN-1202 LM2698 Demo Board 3 Maximum Output Current www.ti.com Figure 3. LM2698 Demo Board Top Layer Layout Figure 4. LM2698 Demo Board Bottom Layer Layout 4 AN-1202 LM2698 Demo Board SNVA040C – September 2001 – Revised April 2013 Submit Documentation Feedback Copyright © 2001–2013, Texas Instruments Incorporated 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. TI warrants performance of its components to the specifications applicable at the time of sale, in accordance with the warranty in TI’s terms and conditions of sale of semiconductor products. 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