National Semiconductor Application Note 2084 Alan Martin August 16, 2010 Introduction Board Specifications The LMZ1420xEXT and LMZ1200xEXT SIMPLE SWITCHER® power modules are easy-to-use DC-DC solution capable of driving up to a 3A load with exceptional power conversion efficiency, output voltage accuracy, line and load regulation. They are available in an innovative package that enhances thermal performance and allows for hand or machine soldering. The LMZ14203EXT/2EXT/1EXT can accept an input voltage rail between 6V and 42V and the LMZ12003EXT/2EXT/1EXT can accept an input voltage rail between 4.5V and 20V. The devices can deliver an adjustable and highly accurate output voltage as low as 0.8V and as high as 6V. The control structure is constant on-time with input voltage feed forward. This creates a nearly constant switching frequency across the input voltage range. The control loop operates well with low ESR output capacitors such as ceramics. An output feed-forward capacitor across the upper feedback resistor trims for optimum transient response. The precision enable input allows for programmable UVLO of the input supply. The external soft-start capacitor facilitates controlled startup output rise time. The LMZ1420xEXT and LMZ1200xEXT family is a reliable and robust solution with the following features: lossless cycle-by-cycle valley current limit to protect for over current or short-circuit fault, thermal shutdown, input under-voltage lock-out, and will start up into a pre-biased output. The LMZ1420xEXT and LMZ1200xEXT families are shock and vibration certified and rated for operation down to –55°C. • • • • • • • • • LMZ1420xEXT VIN = 6V to 42V LMZ1420xEXT enable UVLO = 8V LMZ1420xEXT VOUT = 3.3V LMZ1200xEXT VIN = 4.5V to 20V LMZ1200xEXT enable UVLO = 4.5V LMZ1200xEXT VOUT = 1.8V Operates at full load up to 80°C ambient at 12V input θJA = 20°C / W, θJC = 1.9°C / W Designed on four layers, all four layers are 1 oz. copper weight • The two internal ground planes are identical • Measures 1.705 in. x 3.03 in. (4.33 cm x 7.7cm) and is 62mil (.062”) thick of FR4 laminate material For additional circuit modifications refer to the Design Consideration section of the LMZ1420xEXT or LMZ1200xEXT data sheet. For negative output voltage connections see AN-2027. Additional Footprints Additional component mounting pads are available to experiment with alternative Cin and Cout combinations or a zener clamp on the enable input. See Figure 6 for corresponding schematic locations. AN-2084 30131501 FIGURE 1. Evaluation Board Schematic (LMZ1200xEXT 1.8V application values shown in parentheses) © 2010 National Semiconductor Corporation 301315 LMZ1420xEXT / LMZ1200xEXT Evaluation Board LMZ1420xEXT / LMZ1200xEXT Evaluation Board www.national.com AN-2084 TABLE 1. LMZ1420xEXT Bill of Materials, VIN = 8V to 42V, VOUT = 3.3V, IOUT (MAX) = 3A / 2A / 1A Designator Description Case Size Manufacturer Manufacturer P/N Quantity U1 SIMPLE SWITCHER® TO-PMOD-7 National Semiconductor LMZ14203EXTTZ or LMZ14202EXTTZ or LMZ14201EXTTZ 1 CIN4, CO1 1 µF, X7R, 50V 1206 Taiyo Yuden UMK316B7105KL-T 2 CIN2 10 µF, X5R, 50V 1210 Taiyo Yuden UMK325BJ106MM-T 1 CO2 100 µF, X5R, 6.3V 1210 Taiyo Yuden JMK325BJ107MM-T 1 CSS, CFF 0.022 µF, X7R, 100V 0805 AVX 08051C223JAT2A 2 RENB 11.8k 0805 Panasonic ERJ-6ENF1182V 1 RENT 68.1 kΩ 0805 Panasonic ERJ-6ENF6812V 1 RFBT 3.32 kΩ 0805 Vishay-Dale CRCW08053K32FKEA 1 RFBB 1.07 kΩ 0805 Panasonic CRCW080534K8FKEA 1 RON 61.9 kΩ 0805 Panasonic ERJ-6ENF6192V 1 TABLE 2. LMZ1200xEXT Bill of Materials, VIN = 4.5 to 20V, VOUT = 1.8V, IOUT (MAX) = 3A / 2A / 1A Designator Description Case Size Manufacturer Manufacturer P/N Quantity U1 SIMPLE SWITCHER® TO-PMOD-7 National Semiconductor LMZ12003EXTTZ or LMZ12002EXTTZ or LMZ12001EXTTZ 1 CIN4, CO1 1 µF, X7R, 50V 1206 Taiyo Yuden UMK316B7105KL-T 2 CIN2 10 µF, X5R, 50V 1210 Taiyo Yuden UMK325BJ106MM-T 1 CO2 100 µF, X5R, 6.3V 1210 Taiyo Yuden JMK325BJ107MM-T 1 CSS, CFF 0.022 µF, X7R, 100V 0805 AVX 08051C223JAT2A 2 RENB 11.8k 0805 Panasonic ERJ-6ENF1182V 1 RENT 32.4KΩ 0805 Panasonic ERJ-6ENF3242V 1 RFBT 1.87 kΩ 0805 Vishay-Dale CRCW08051K87FKEA` 1 RFBB 1.50 kΩ 0805 Panasonic CRCW08051K50FKEA 1 RON 32.4KΩ 0805 Panasonic ERJ-6ENF3242V 1 Performance Characteristics LMZ14203EXT Load and Line Regulation LMZ12003EXT Load and Line Regulation 30131504 30131505 www.national.com 2 AN-2084 LMZ14203EXT Efficiency LMZ12003EXT Efficiency 30131502 30131503 LMZ14202EXT Efficiency LMZ12002EXT Efficiency 30131520 30131521 LMZ14201EXT Efficiency LMZ12001EXT Efficiency 30131522 30131523 3 www.national.com AN-2084 LMZ14203EXT Thermal Derating LMZ12003EXT Thermal Derating 30131515 30131516 LMZ14202EXT Thermal Derating LMZ12002EXT Thermal Derating 30131524 30131525 LMZ14201EXT Thermal Derating LMZ12001EXT Thermal Derating 30131527 30131526 www.national.com 4 LMZ12003EXT Current Limit VOUT = 1.8V 30131528 30131529 LMZ14202EXT Current LimitVOUT = 3.3V LMZ12002EXT Current Limit VOUT = 1.8V 30131530 30131531 LMZ14201EXT Current Limit VOUT = 3.3V LMZ12001EXT Current Limit VOUT = 1.8V 30131533 30131532 5 www.national.com AN-2084 LMZ14203EXT Current Limit VOUT = 3.3V AN-2084 LMZ14203EXT Startup VIN = 12V LMZ12003EXT Startup VIN = 12V 30131535 30131534 LMZ14203EXT Output Ripple VOUT = 3.3V IOUT = 3A, BW = 200 MHz LMZ14203EXT Transient Response VIN = 24V VOUT = 3.3V, 0.6 A to 3A Step 30131518 30131517 PCB Layout Diagrams Gerber and CAD files can be download from the LMZ14203EXT product folder. 30131509 FIGURE 2. Top Layer www.national.com 6 AN-2084 30131510 FIGURE 3. Internal Layer I (Ground) Heat Sinking Layer 30131511 FIGURE 4. Internal Layer II (Ground) Heat Sinking Layer 30131512 FIGURE 5. Bottom Layer (Ground and Routing) Heat Sinking Layer 7 www.national.com AN-2084 30131513 FIGURE 6. LMZ14203EXT PCB CAD package schematic DNS = Component not installed www.national.com 8 AN-2084 Notes 9 www.national.com LMZ1420xEXT / LMZ1200xEXT Evaluation Board Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: www.national.com Products Design Support Amplifiers www.national.com/amplifiers WEBENCH® Tools www.national.com/webench Audio www.national.com/audio App Notes www.national.com/appnotes Clock and Timing www.national.com/timing Reference Designs www.national.com/refdesigns Data Converters www.national.com/adc Samples www.national.com/samples Interface www.national.com/interface Eval Boards www.national.com/evalboards LVDS www.national.com/lvds Packaging www.national.com/packaging Power Management www.national.com/power Green Compliance www.national.com/quality/green Switching Regulators www.national.com/switchers Distributors www.national.com/contacts LDOs www.national.com/ldo Quality and Reliability www.national.com/quality LED Lighting www.national.com/led Feedback/Support www.national.com/feedback Voltage References www.national.com/vref Design Made Easy www.national.com/easy www.national.com/powerwise Applications & Markets www.national.com/solutions Mil/Aero www.national.com/milaero PowerWise® Solutions Serial Digital Interface (SDI) www.national.com/sdi Temperature Sensors www.national.com/tempsensors SolarMagic™ www.national.com/solarmagic PLL/VCO www.national.com/wireless www.national.com/training PowerWise® Design University THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. 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