LM2833ZMYEVAL

User's Guide SNVA345B – November 2008 – Revised April 2013 AN-1844 LM2833Z MSOP-PowerPAD Demo Board 1 Introduction The LM2833Z MSOP-PowerPAD demo board is designed to demonstrate the capabilities of the LM2833Z 3MHz switching regulator in an MSOP PowerPAD-10 package. The demo board is configured to provide an output of 1.2V at up to 3A from an input voltage range of 3V to 5.5V. The board is thermally optimized with the small solution size of 1.2" X 1.1", shown in the demo board schematic in Figure 1. The output voltage can be configured to a different value by changing the ratio between R1 and R2 according to the following equation: R1 = R2 x (VOUT / VFB - 1) (1) The feedback voltage VFB is regulated at 0.60V typically. The board has C5 reserved for two purposes given different application scenarios. First, at high VOUT applications, the control loop bandwidth is not as large as at low VOUT. Adding C5 at high VOUT can significantly improve the load step response by boosting the loop bandwidth without significantly compromising phase margin. Secondly, it also helps to minimize output voltage overshoot during sluggish startup, short circuit release, and recovery from thermal shutdown, since it creates a feed-forward path between VOUT and VFB, thus speeding up Gm-amplifier recovery. In practice, for a few kΩ of voltage divider bottom resistor R2, a 47nF ceramic capacitor is usually a good choice for C5. Note for applications where VOUT is close to VFB, since R1 is small, the effectiveness of adding C5 becomes decreasingly appreciable. Therefore, other measures need to be taken to achieve the desired performance. For example, to minimize output overshoot during slow startup at high VOUT, an alternative approach is to apply a separate signal at the EN terminal after VIN is fully established. Another component which is not populated on the board is C4, which is reserved for applications where a large output capacitor is desired. Table 1 lists the bill of materials of this demo board. The measured performance characteristics and layout of this board are also included below. 2 Powering up the Board Powering up the LM2833Z MSOP-PowerPAD demo board is a single-step procedure, simply by applying a DC voltage of 3V to 5.5V to VIN and GND terminals. By default, VINC is connected to VIN through a low pass filter to remove any high frequency noise present at the input. EN is connected to VINC through a 100kΩ resistor. A separate logic signal at the EN terminal can be used, if startup and shutdown need to be controlled. A load can be connected between VOUT and GND terminals before or after the board is powered up. At VOUT of 1.2V, the internal soft-start circuit can bring up VOUT smoothly regardless of load or input voltage. The LM2833Z is designed to skip some pulses at very light loads to maintain output voltage regulation. Depending on load levels, the circuit may operate in either discontinuous or continuous conduction mode. All trademarks are the property of their respective owners. SNVA345B – November 2008 – Revised April 2013 Submit Documentation Feedback AN-1844 LM2833Z MSOP-PowerPAD Demo Board Copyright © 2008–2013, Texas Instruments Incorporated 1 Typical Performance Characteristics www.ti.com Figure 1. LM2833Z MSOP-PowerPAD Demo Board Schematic 3 Typical Performance Characteristics Efficiency vs Load Current 2 AN-1844 LM2833Z MSOP-PowerPAD Demo Board Efficiency vs Load Current SNVA345B – November 2008 – Revised April 2013 Submit Documentation Feedback Copyright © 2008–2013, Texas Instruments Incorporated Typical Performance Characteristics www.ti.com Load Regulation Startup (VIN Slew Rate = 0.2V/µs ) Startup (VIN Slew Rate = 1V/ms ) Steady-state (CCM Mode) Steady-state (DCM Mode) Steady-state (Pulse Skipping) SNVA345B – November 2008 – Revised April 2013 Submit Documentation Feedback AN-1844 LM2833Z MSOP-PowerPAD Demo Board Copyright © 2008–2013, Texas Instruments Incorporated 3 Typical Performance Characteristics 4 www.ti.com Load Transient (Slew Rate = 0.1A/µs) (C5 not installed) Load Transient (Slew Rate = 0.1A/µs) (C5 = 47nF) Line Transient Loop Gain AN-1844 LM2833Z MSOP-PowerPAD Demo Board SNVA345B – November 2008 – Revised April 2013 Submit Documentation Feedback Copyright © 2008–2013, Texas Instruments Incorporated Layout www.ti.com 4 Layout Figure 2. Top Layer and Top Overlay Figure 3. Internal Plane 1 (GND) SNVA345B – November 2008 – Revised April 2013 Submit Documentation Feedback AN-1844 LM2833Z MSOP-PowerPAD Demo Board Copyright © 2008–2013, Texas Instruments Incorporated 5 Layout www.ti.com Figure 4. Bottom Layer Figure 5. Internal Plane 2 (VIN) 6 AN-1844 LM2833Z MSOP-PowerPAD Demo Board SNVA345B – November 2008 – Revised April 2013 Submit Documentation Feedback Copyright © 2008–2013, Texas Instruments Incorporated Bill of Materials www.ti.com 5 Bill of Materials Table 1. Bill of Materials Part ID Part Value Part Number Manufacturer U1 L1 3MHz 3.0A buck regulator, MSOP PowerPAD-10 LM2833 Texas Instruments 1.0µH, 4A, 5x5x2mm3 NP04SZB1R0N Taiyo Yuden C1 22µF, 6.3V, X5R, 1206 C3216X5R0J226MT TDK C2 0.22µF, 10V, X7R, 0805 GRM216R71A224KC01D Murata C3 47µF, 6.3V, X5R, 1206 JMK316BJ476ML-T Taiyo Yuden C4 Open C5 Open D1 Schottky, 30V, 3A, 3-4E1A CMS01 Toshiba R1 2.00kΩ, 1%, 1/8W, 0805 CRCW08052K00FKEA Vishay R2 2.00kΩ, 1%, 1/8W, 0805 CRCW08052K00FKEA Vishay R3 10.0Ω, 1%, 1/8W, 0805 CRCW080510R0FKEA Vishay R4 100kΩ, 1%, 1/8W, 0805 CRCW0805100KFKEA Vishay SNVA345B – November 2008 – Revised April 2013 Submit Documentation Feedback AN-1844 LM2833Z MSOP-PowerPAD Demo Board Copyright © 2008–2013, Texas Instruments Incorporated 7 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. 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