LM2852Y-2.5EVAL

User's Guide SNVA095B – February 2005 – Revised April 2013 AN-1343 LM2852 Evaluation Board (500kHz version) 1 Introduction In this evaluation board for the LM2852Y, three output voltage options are available and all three come with the same bill of materials. The board may be configured in multiple ways providing various enabling schemes, split-rail operation and filtering options. The LM2852 is a 2A step-down buck converter belonging to TI’s SIMPLE SYNCHRONOUS® family. The LM2852 input voltage can range from 2.85V to 5.5V. Output voltages are factory set from 0.8V to 3.3V in 100mV increments. On-chip type-three compensation facilitates low component count power supply design. This evaluation board enables the power supply designer to investigate various functional configurations. 2 PVIN and AVIN The input voltage to the LM2852 is connected to two PVIN pins and an AVIN pin. PVIN is the supply connected to the output power switches; AVIN powers the controller logic of the switcher. Since PVIN and AVIN are dedicated pins on the chip, split rail operation is possible. For example, AVIN can be set to 5V and PVIN to 3.3V. Jumper J1 on the evaluation board is used to short together the AVIN and PVIN board inputs. 3 Enable (EN) The LM2852 enable pin is internally pulled up so that the part is enabled anytime the input voltage exceeds the UVLO threshold. The evaluation board includes an input for enable so the user may set the voltage on the enable pin. Jumper J2 also may be used to short the enable pin to AVin. Resistor, Rp may be used as a pull down resistor to set the enable input to low. 4 Cf and Rf Components Cf and Rf may be used to low-pass-filter the AVIN input. Filtering AVIN may improve line and load regulation by reducing interfering signals on AVIN. 10 Ω and 1 µF are typical filter components for AVIN. 5 CIN and CINX This evaluation board provides two capacitor footprints for the CIN function. The larger footprint holds the bulk of the CIN capacitor, for example 47 µF. Additional high frequency filtering may also be accomplished by adding a smaller capacitor – CINX. A 1 µF or 100 nF capacitor is commonly used for high frequency filtering. 6 CSS The soft-start capacitor is used to control the start up behavior of the switching regulator. A 2.7 nF capacitor yields approximately a 3 ms start up time. 7 Output Filter - L1, CO1 and CO2 Since the LM2852 uses on-chip compensation, the output filter component values must be restricted to a certain range. The data sheet includes a table and information on component selection. Generally, the output capacitors must have ESR values commonly found in Tantalum and non-Tantalum solution, Niobium Oxide capacitors. All trademarks are the property of their respective owners. SNVA095B – February 2005 – Revised April 2013 Submit Documentation Feedback AN-1343 LM2852 Evaluation Board (500kHz version) Copyright © 2005–2013, Texas Instruments Incorporated 1 Board Schematic 8 www.ti.com Board Schematic U1 Cf Rf AVIN 1 2 J2 EN J1 3 4 RP CSS 5 6 PVIN CIN 7 CINX AVIN SNS EN NC SGND NC SS PGND NC PGND PVIN PVIN SW 14 13 12 11 10 9 SW L1 8 VOUT C + O2 C + O1 GND Table 1. Bill of Materials 2 ID Part Number Type Size U1 LM2852, LM2852 or LM2852 2A Buck HTSSOP-14 L1 DO3316P-153 Inductor CO1 NOSD107M006R0100 Capacitor Parameters Qty Vendor 1 TI 15 µH 1 Coilcraft 100 µF 1 AVX CO2 Not Populated CIN GRM32ER60J476ME20B Capacitor 1210 47µF/X5R/6.3V 0 1 Murata CINX GRM21BR71C105KA01B Capacitor 0805 1µF/X7R/16V 1 Murata CSS VJ0805Y272KXXA Capacitor 0805 2.7nF/X7R/25V 1 Vishay-Vitramon Rf CRCW060310R0F Resistor 0603 10Ω ±10% 1 Vishay-Dale Cf GRM21BR71C105KA01B Capacitor 0805 1µF/X7R/16V 1 Murata J1 CRCW06030R0F Resistor 0603 0Ω 1 Vishay-Dale J2 Not Populated 0 RP Not Populated 0 AN-1343 LM2852 Evaluation Board (500kHz version) SNVA095B – February 2005 – Revised April 2013 Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated PCB Layouts www.ti.com 9 PCB Layouts Figure 1. Top Layer Figure 2. Bottom Layer 96 PVIN = 3.3V EFFICIENCY (%) 94 92 90 PVIN = 5.0V 88 86 84 0.1 1.0 10 ILOAD (A) Figure 3. Typical Efficiency for 2.5V Output SNVA095B – February 2005 – Revised April 2013 Submit Documentation Feedback AN-1343 LM2852 Evaluation Board (500kHz version) Copyright © 2005–2013, Texas Instruments Incorporated 3 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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