LM26400YEVAL

www.ti.com Table of Contents User’s Guide LM26400Y Step-Down Converter Evaluation Module User's Guide Table of Contents 1 Introduction.............................................................................................................................................................................2 2 Powering Up The Board......................................................................................................................................................... 2 3 Board Schematic.................................................................................................................................................................... 3 4 PCB Layout..............................................................................................................................................................................5 5 Typical Performance Characteristics....................................................................................................................................7 6 Revision History......................................................................................................................................................................8 Trademarks All trademarks are the property of their respective owners. SNOA483B – MARCH 2007 – REVISED DECEMBER 2021 LM26400Y Step-Down Converter Evaluation Module User's Guide Submit Document Feedback Copyright © 2021 Texas Instruments Incorporated 1 Introduction www.ti.com 1 Introduction The LM26400Y demonstration board was designed to provide two 2A outputs at 1.2V and 2.5V respectively. It uses the HTSSOP package option of the LM26400Y for easier probing. The design emphasizes on the compactness of the LM26400Y PCB layout and is thermally optimized. The total solution size is about 20mm by 30mm. The board supports the conversion from an input voltage ranging from 5V to 20V down to output voltages of 1.2V and 2.5V. With the availability of a separate 5V rail and a couple of small bootstrap diodes, the board also supports an input voltage down to 3.3V with 2A output currents. The EN pins are pulled up to VIN by default for easy evaluation but can also be easily controlled by external logic. The board also has two small CFF capacitors (C12 and C13) installed for improved load step response and elimination of output voltage overshoot after a short-circuit release. The board’s specifications are: Input Voltage: 5V to 20V Output Voltages: 1.2V and 2.5V Maximum load current: 2A/output Minimum load current: 0A Peak Current Limit: ≊ 3A at 25°C Measured Efficiency: 83% (VIN = 5V, IOUT2 = 2A) Nominal Switching Frequency: 520 kHz Size: 2 in. x 2 in. 2 Powering Up The Board Since the EN pins are directly tied to the input voltage, starting up the board is a single-step procedure. Simply connect a voltage rail between 5V and 20V to the VIN and GND terminals and there should be 1.2V and 2.5V output at the corresponding terminals. Certain bench-top power supplies upon powering up may shoot up to their maximum output voltages momentarily before settling to the programmed value. If their maximum voltage is above 22V, it can damage the LM26400Y demonstration board. In this case, either connect the board after the input power supply is powered up, or use the current limit knob of the power supply to bring up the input voltage. The linear soft-start ramps for the two output voltages should last about 1ms and 2ms. Load can be applied prior to power-up. If no load is applied, the two channels will operate in pulse skipping mode or discontinuous conduction mode. If an output is shorted either before or after start-up, removal of the short-circuit condition should bring the corresponding output back to normal voltage. If additional output capacitors are desired, C8 and C9 on the back of the board are reserved for that purpose. If it is desired to control the start-up and shutdown timing, connect the logic signals to the EN1 and/or EN2 pads on the back of the board. Make sure the voltages on the EN pads are never higher than VIN. If only a soft-start slope needs to be adjusted, simply change the corresponding SS capacitor (C5 or C6). To operate between 3.3V and 5V of input voltage, populate D3 and D4 (on the back of the board) each with a SOT-23 Schottky diode such as the BAT54 and apply a 5V supply to the "5V_Bias" pad on the back. Do not exceed 6V on the 5V bias. The LM26400Y device itself can work with an input voltage as low as 3V. The demonstration board when using an external bootstrap bias can operate down to 3.3V under room temperature. This extra 0.3V requirement is due to the large duty cycle in the 2.5V channel being too close to the maximum allowed. 2 LM26400Y Step-Down Converter Evaluation Module User's Guide SNOA483B – MARCH 2007 – REVISED DECEMBER 2021 Submit Document Feedback Copyright © 2021 Texas Instruments Incorporated www.ti.com Board Schematic 3 Board Schematic SNOA483B – MARCH 2007 – REVISED DECEMBER 2021 LM26400Y Step-Down Converter Evaluation Module User's Guide Submit Document Feedback Copyright © 2021 Texas Instruments Incorporated 3 Board Schematic www.ti.com Table 3-1. Bill of Materials Item 4 Designator Description Manufacturer Part No. Qty. 1 C5, C6, C12, C13 0.022µF, 6.3V, X5R, 10%, 0402 Kemet C0402C223K9PACTU 4 2 C2, C3, C7 0.1µF, 25V, X5R, 10%, 0402 Taiyo Yuden TMK105BJ104KV-F 3 3 C1 10µF, 25V, X5R, 20%, 1210 Taiyo Yuden TMK325BJ106MM-T 1 4 C11 47µF, 6.3V, X5R, 20%, 1210 Taiyo Yuden JMK325BJ476MM-T 1 5 C4 100µF, 6.3V, X5R, 20%, 1210 Taiyo Yuden JMK325BJ107MM-T 1 6 D1, D2 2A, 30V, SMB IR 20BQ030TRPBF 2 7x7x2.8mm3 7 L1 5µH, 2.2A, 23mΩ, Sumida CDRH6D26NP-5R0NC 1 8 L2 8.7µH, 2.2A, 25mΩ, 7x7x4mm3 Sumida CDRH6D38NP-8R7NC 1 9 R1 4.7Ω, 1%, 0402 Vishay CRCW04024R70FNED 1 10 R2, R3, R5 5.9kΩ, 1%, 0402 Vishay CRCW040259R0FKED 3 11 R4, R6, R7 18.7kΩ, 1%, 0402 Vishay CRCW0402187RFKED 3 12 TP1-TP6 0.094" Diameter Solder Terminal Cambion 160-1026-02-01-00 6 13 U1 Dual 2A, 20V, 500kHz PWM Switcher, HTSSOP-16 TI LM26400 1 LM26400Y Step-Down Converter Evaluation Module User's Guide SNOA483B – MARCH 2007 – REVISED DECEMBER 2021 Submit Document Feedback Copyright © 2021 Texas Instruments Incorporated www.ti.com PCB Layout 4 PCB Layout Figure 4-1. Top Copper Figure 4-3. Power Plane Figure 4-2. Ground Plane Figure 4-4. Bottom Copper SNOA483B – MARCH 2007 – REVISED DECEMBER 2021 LM26400Y Step-Down Converter Evaluation Module User's Guide Submit Document Feedback Copyright © 2021 Texas Instruments Incorporated 5 PCB Layout 6 www.ti.com Figure 4-5. Top Silkscreen Figure 4-6. Bottom Silkscreen Figure 4-7. Top Soldermask Figure 4-8. Bottom Soldermask LM26400Y Step-Down Converter Evaluation Module User's Guide SNOA483B – MARCH 2007 – REVISED DECEMBER 2021 Submit Document Feedback Copyright © 2021 Texas Instruments Incorporated www.ti.com Typical Performance Characteristics 5 Typical Performance Characteristics Figure 5-1. Efficiency Figure 5-2. Efficiency Figure 5-3. Start-up Figure 5-4. Steady State (Ch1 = DCM, Ch2 = Pulse Skipping) Figure 5-5. Steady State (Ch1 = CCM, Ch2 = DCM) Figure 5-6. Load Step Response (Slew Rate = 0.25A/µs) SNOA483B – MARCH 2007 – REVISED DECEMBER 2021 LM26400Y Step-Down Converter Evaluation Module User's Guide Submit Document Feedback Copyright © 2021 Texas Instruments Incorporated 7 Revision History www.ti.com 6 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 (December 2021) Page • Updated the numbering format for tables, figures, and cross-references throughout the document. ................2 • Updated the user's guide title............................................................................................................................. 2 8 LM26400Y Step-Down Converter Evaluation Module User's Guide SNOA483B – MARCH 2007 – REVISED DECEMBER 2021 Submit Document Feedback Copyright © 2021 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. You are solely responsible for (1) selecting the appropriate TI products for your application, (2) designing, validating and testing your application, and (3) ensuring your application meets applicable standards, and any other safety, security, regulatory or other requirements. These resources are subject to change without notice. TI grants you permission to use these resources only for development of an application that uses the TI products described in the resource. Other reproduction and display of these resources is prohibited. No license is granted to any other TI intellectual property right or to any third party intellectual property right. TI disclaims responsibility for, and you will fully indemnify TI and its representatives against, any claims, damages, costs, losses, and liabilities arising out of your use of these resources. TI’s products are provided subject to TI’s Terms of Sale or other applicable terms available either on ti.com or provided in conjunction with such TI products. TI’s provision of these resources does not expand or otherwise alter TI’s applicable warranties or warranty disclaimers for TI products. TI objects to and rejects any additional or different terms you may have proposed. IMPORTANT NOTICE Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265 Copyright © 2022, Texas Instruments Incorporated