AN-2074

LMZ1050xEXT Evaluation Board LMZ1050xEXT Evaluation Board National Semiconductor Application Note 2074 Yang Zhang August 16, 2010 Introduction The LMZ1050xEXT SIMPLE SWITCHER® power module is a complete, easy-to-use DC-DC solution capable of driving up to 3A, 4A, or 5A load with exceptional power conversion efficiency, output voltage accuracy, line and load regulation. The LMZ1050xEXT is available in an innovative package that enhances thermal performance and allows for hand or machine soldering. The LMZ1050xEXT can accept an input voltage rail between 2.95V and 5.5V and deliver an adjustable and highly accurate output voltage as low as 0.8V. One megahertz fixed frequency PWM switching provides a predictable EMI characteristic. Two external compensation components can be adjusted to set the fastest response time, while allowing the option to use ceramic and/or electrolytic output capacitors. Externally programmable soft-start capacitor facilitates controlled startup. The LMZ1050xEXT is a reliable and robust solution with the following features: lossless cycle-by-cycle peak current limit to protect for over current or short-circuit fault, thermal shutdown, input under-voltage lock-out, and pre-biased startup. Evaluation Board Design Concept The evaluation board is designed to demonstrate low conducted noise on the input and output lines, as seen in Figure 11 and Figure 14. Four input capacitors (Cin1 - C in4) and three output capacitors (Co1 - Co3) are populated for this purpose. All the input and output filter capacitors are not necessary to comply with radiation standards. For a circuit example that passes radiated emissions standards (EN55022, class B) please refer to Figure 19. Additionally, Cin5 is present to reduce the resonance of the input line produced by the inductance and resistance in the cables connecting the bench power supply to the evaluation board and the input capacitors. Additional Component Footprints When the tracking feature of the LMZ1050xEXT is used, remove the soft-start capacitor CSS and use a resistor divider on designators Rtrkb and Rtrkt. The ground and Vtrk post have been provided for easy connection. The LMZ1050xEXT eval board incorporates a precision enable circuit which is pulled high by a 100 kΩ pull up resistor to VIN. This allows the user to pull low on the enable pin to ground. The top enable resistor is Rent and the bottom enable resistor is Renb. Refer to the Design Guideline and Operating Description section of the LMZ1050xEXT data sheet for detailed design implementation. Select FPGAs specify input inrush currents for particular power-up sequences and others require sequencing rails to avoid start-up or latch-up problems. To prevent early turn-on of the LMZ1050xEXT in systems with multiple power rails, precision enable and tracking are useful as the main input voltage rail rises at power-up. Board Specifications • • • VIN = 2.95V to 5.5V VOUT = 2.5V (default output voltage setting, refer to Table 2 for other output settings) ±2.5% feedback voltage accuracy at 2.5V output (Including line and load regulation from TJ = -55°C to 125°C) ±1.63% feedback voltage accuracy over temperature IOUT = 0A to 3A, 4A, and 5A θJA = 20°C/W, θJC = 1.9°C/W Designed on four layers, the top and bottom layers are 1oz. copper and the two inner layers are 1/2 oz. copper weight Measures 2.25 in. x 2.25 in. (5.8 cm x 5.8 cm) and is 62mil (.062”) thick on a FR4 laminate • • • • • AN-2074 © 2010 National Semiconductor Corporation 301280 www.national.com AN-2074 Component Circuit Schematic 30128017 FIGURE 1. Component Schematic for Evaluation Board TABLE 1. Bill of Materials for Evaluation Board, VIN = 3.3V to 5V, VOUT = 2.5V Designator U1 Cin1 Cin2, CO1 Cin3, CO2 Cin4 CO3 Rfbt Rfbb Rcomp Ccomp Ren1 CSS Description SIMPLE SWITCHER® 1 µF, X7R, 16V 4.7 µF, X5R, 6.3V 22 µF, X5R, 16V 47 µF, X5R, 6.3V 100 µF, X5R, 6.3V 75 kΩ 34.8 kΩ 1.1 kΩ 180 pF, ±5%, C0G, 50V 100 kΩ 10 nF, ±5%, C0G, 50V Case Size TO-PMOD-7 0805 0805 1210 1210 1812 0805 0805 0805 0603 0805 0805 Manufacturer National Semiconductor TDK TDK TDK TDK TDK Vishay Dale Vishay Dale Vishay Dale TDK Vishay Dale TDK Manufacturer P/N LMZ10503/4/5EXTTZ C2012X7R1C105K C2012X5R0J475K C3225X5R1C226M C3225X5R0J476M C4532X5R0J107M CRCW080575K0FKEA CRCW080534K8FKEA CRCW08051K10FKEA C1608C0G1H181J CRCW0805100KFKEA C2012C0G1H103J Quantity 1 1 2 2 1 1 1 1 1 1 1 1 TABLE 2. Output Voltage Setting (Rfbt = 75 kΩ) VOUT 3.3 V 2.5 V 1.8 V 1.5 V 1.2 V 0.9 V Rfbb 23.7 kΩ 34.8 kΩ 59 kΩ 84.5 kΩ 150 kΩ 590 kΩ www.national.com 2 AN-2074 Complete Circuit Schematic 30128024 FIGURE 2. Complete Evaluation Board Schematic 3 www.national.com AN-2074 Connection Diagram 30128015 FIGURE 3. Efficiency Measurement Setup 30128016 FIGURE 4. Output Voltage Ripple Measurement Setup Efficiency vs. Load Current LMZ10504EXT & LMZ10505EXT, VOUT = 2.5V, TAMB = 25°C Efficiency vs. Load Current LMZ10503EXT, VOUT = 2.5V, TAMB = 25°C 30128028 30128031 www.national.com 4 AN-2074 Performance Characteristics 30128029 30128030 FIGURE 5. Current Derating vs. Ambient Temperature LMZ10503EXT, VIN = 5.0V, θJA = 20°C/W FIGURE 8. Current Derating vs. Ambient Temperature LMZ10503EXT, VIN = 3.3V, θJA = 20°C/W 30128022 30128023 FIGURE 6. Current Derating vs. Ambient Temperature LMZ10504EXT, VIN = 5.0V, θJA = 20°C/W FIGURE 9. Current Derating vs. Ambient Temperature LMZ10504EXT, VIN = 3.3V, θJA = 20°C/W 30128032 30128033 FIGURE 7. Current Derating vs. Ambient Temperature LMZ10505EXT, VIN = 5.0V, θJA = 20°C/W FIGURE 10. Current Derating vs. Ambient Temperature LMZ10505EXT, VIN = 3.3V, θJA = 20°C/W 5 www.national.com AN-2074 30128018 30128020 FIGURE 11. Output Voltage Ripple VIN = 5V, VOUT = 2.5V, IOUT = 3A, 4A, & 5A LMZ10503EXT / LMZ10504EXT / LMZ10505EXT FIGURE 14. Output Voltage Ripple VIN = 3.3V, VOUT = 2.5V, IOUT = 3A, 4A, & 5A LMZ10503EXT / LMZ10504EXT / LMZ10505EXT 30128037 30128036 FIGURE 12. Load Transient Response VIN = 5.0V, VOUT = 2.5V LMZ10503EXT, IOUT = 400 mA to 2.7A, 20 MHz Bandwidth Limit FIGURE 15. Load Transient Response VIN = 3.3V, VOUT = 2.5V LMZ10503EXT, IOUT = 300 mA to 2.7A, 20 MHz Bandwidth Limit 30128019 30128021 FIGURE 13. Load Transient Response VIN = 5V, VOUT = 2.5V LMZ10504EXT, IOUT = 400 mA to 3.6A, 20 MHz Bandwidth Limit FIGURE 16. Load Transient Response VIN = 3.3V, VOUT = 2.5V LMZ10504EXT, IOUT = 400 mA to 3.6A, 20 MHz Bandwidth Limit www.national.com 6 AN-2074 30128035 30128034 FIGURE 17. Load Transient Response VIN = 5.0V, VOUT = 2.5V LMZ10505EXT, IOUT = 500 mA to 4.5A, 20 MHz Bandwidth Limit FIGURE 18. Load Transient Response VIN = 3.3V, VOUT = 2.5V LMZ10505EXT, IOUT = 500 mA to 4.5A, 20 MHz Bandwidth Limit 7 www.national.com AN-2074 Circuit Example: Complies with EN55022 Class B Radiated Emissions 30128025 FIGURE 19. Component Schematic, VIN = 5V, VOUT = 2.5V, Complies with EN55022 Class B Radiated Emissions TABLE 3. Bill of Materials Designator U1 Cin1 Cin2 Cin3 CO1 Rfbt Rfbb Rcomp Ccomp CSS Description SIMPLE SWITCHER® 1 µF, X7R, 16V 4.7 µF, X5R, 6.3V 47 µF, X5R, 6.3V 100 µF, X5R, 6.3V 75 kΩ 34.8 kΩ 1.1 kΩ 180 pF, ±5%, C0G, 50V 10 nF, ±5%, C0G, 50V Case Size TO-PMOD-7 0805 0805 1210 1812 0805 0805 0805 0603 0805 Manufacturer National Semiconductor TDK TDK TDK TDK Vishay Dale Vishay Dale Vishay Dale TDK TDK Manufacturer P/N LMZ10503/4/5EXTTZ C2012X7R1C105K C2012X5R0J475K C3225X5R0J476M C4532X5R0J107M CRCW080575K0FKEA CRCW080534K8FKEA CRCW08051K10FKEA C1608C0G1H181J C2012C0G1H103J Quantity 1 1 1 1 1 1 1 1 1 1 30128038 30128026 FIGURE 20. Radiated Emissions (EN55022, Class B) VIN = 5V, VOUT = 2.5V, IOUT = 3A Tested on LMZ10503EXT Evaluation Board FIGURE 21. Radiated Emissions (EN55022, Class B) VIN = 5V, VOUT = 2.5V, IOUT = 4A Tested on LMZ10504EXT Evaluation Board www.national.com 8 AN-2074 30128027 FIGURE 22. Radiated Emissions (EN55022, Class B) VIN = 5V, VOUT = 2.5V, IOUT = 5A Tested on LMZ10505EXT Evaluation Board 9 www.national.com AN-2074 PCB Layout Diagram 30128007 FIGURE 23. Top Layer 30128008 FIGURE 24. Internal Layer I (Ground) www.national.com 10 AN-2074 30128011 FIGURE 25. Internal Layer II (Ground) 30128013 FIGURE 26. 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