National Semiconductor Application Note 2032 Alan Martin January 22, 2010 Description Demo Board Features The LMZ14203 SIMPLE SWITCHER power module is a complete, easy to use step-down DC-DC solution capable of driving up to 3A load. The LMZ14203 is available in an innovative, easy to use package that enhances thermal performance and allows for hand or machine soldering. The LMZ14203 demo board can accept an input voltage rail between 8V and 42V and deliver an adjustable and highly accurate output voltage as low as 0.8V. The LMZ14203 only requires three external resistors and four external capacitors to complete the power solution. The LMZ14203 is a reliable and robust solution with the following protection features: thermal shutdown, input under-voltage lockout, output overvoltage protection, short-circuit protection, output current limit, and allows startup into a pre-biased output. A single resistor adjusts switching frequency up to 1 MHz. • • • • • • • • • • • • • • Packaging Highlights • • • • • Power input voltage range 6V-42V UVLO programmed at 8V Adjustable output voltage range 0.8V to 6V Up to 3A output current Integrated shielded inductor in module Efficiency up to 92% All ceramic capacitor design No loop compensation required Starts into pre-biased loads Short circuit protection Thermal Shutdown Only 9 external passives plus module Max 78°C ambient at full load 2 layer low cost assembly Typical Applications 7 lead module package (Similar to TO-263) Single exposed die attach pad for enhanced thermal performance 10.2 x 13.8 x 4.6 mm module package High power density 1.7” x 2.3” reduced size demo board form factor • • • • • Point of load conversions from 12V and 24V input rail Space constrained applications Industrial controls Telecom Networking equipment © 2010 National Semiconductor Corporation 30114402 Back View 301144 www.national.com AN-2032 30114401 Front View LMZ14203 3A Demo Board SIMPLE SWITCHER® Power Module Quick Start Guide LMZ14203 3A Demo Board SIMPLE SWITCHER® Power Module Quick Start Guide AN-2032 Absolute Maximum Module Ratings Demo Board Operating Ratings VIN, RON to GND -0.3V to 47 VIN 6V to 42V EN, FB, SS to GND VOUT (Default setting) 3.3V IOUT 0A to 3A -0.3V to 7V Module Operating Ratings VIN EN (Input on demo 0V to 42V board post) 6V to 42V EN (Input on pin 3 0V to 6.5V module pin) UVLO setting on ENable input 8V Junction Temperature Range (Tj) Soft-start time 2.2 mSec Operating Temperature Range (Tj) - 40C to +78C (at full 3A load) - 40C to +125C Demo Board Schematic 30114403 www.national.com 2 AN-2032 Demo Board Bill of Materials Ref Des Description Case RON 61.9 kohm 1% resistor 603 RENT 68.1 kohm 1% resistor 603 RENB 11.8 kohm 1% resistor 603 RFBT 3.32 kohm 1% resistor 603 RFBB 1.07 kohm 1% resistor 603 CFF 0.022 uF 50V X7R 603 ceramic capacitor CSS 0.022 uF 50V X7R 603 ceramic capacitor CIN1 10 uF 50V X5R 1210 ceramic capacitor UMK325BJ106M M-T CO1 1.0 uF 50V X7R 1206 ceramic capacitor UMK316B7105KL -T CO2 100 uF 6.3V X5R 1210 ceramic capacitor JMK325BJ107M M-T U1 LMZ14203 SIMPLE SWITCHER Power Module LMZ14203TZADJ TOPMOD Manufacturer Part Number Alternate resistor values for alternative output voltages VOUT RFBT RFBB RON 6 2.49k 3.83k 124k 5 5.62k 1.07k 100k 3.3 3.32k 1.07k 61.9k 2.5 2.26k 1.07k 47.5k 1.8 1.87k 1.50k 32.4k 1.5 1.00k 1.13k 28.0k 1.2 4.22k 8.45k 22.6k 0.8 0.0K 39.2k 24.9k Quiescent current: If the Enable post is disconnected, the module will be disabled and about 20 uA of supply current will flow from Vin to ground while in the disabled mode. With the enable input connected to Vin via the 68.1K/11.8K divider there will be about 1.5 mA of no-load quiescent current into the Vin input. Additional current flows into the enable divider string. Demo Board Hookup VOUT Connect the load to VOUT and one of the GND posts. The module can source up to a 3A load current. VIN : Connect Vin to a positive voltage in the 8 to 42V range. Connect the negative terminal of the source supply to one of the posts labeled GND. En: The Enable input post is configured for direct connection to the Vin post. The on-board resistive voltage divider is chosen such that when connected to 42V that the enable input at pin 3 of the module will not exceed 6.5V. With the chosen resistor values this results in an under voltage lockout level of 8 V input. The top enable resistor is RENT (aka REN1) and the bottom enable resistor is RENB (aka REN2). The bottom enable resistor may have a location for a shunt zener clamp (Labeled D1 OPT in the silkscreen - Included only in the later revisions of the assembly.) Demo Board Passive Components Soft-start capacitor The soft-start capacitor controls the rise time of the output voltage when power is first applied and following the clearing of a fault mode. Feedback dividerRegulator output voltage is programmed though the selection of the two resistors, RFBT ( aka RFB1) and RFB (aka RFB2) A feed forward capacitor (CFF) is located in parallel with the upper feedback divider resistor. This capacitor improves the step response to abrupt changes in 3 www.national.com AN-2032 load current. Refer to the table above when modifying the board for a different output voltage. Resistor values shown will minimize error in output voltage setting. RON Resistor: The primary function of the RON resistor is to set the On-Time interval of the internal control section switching cycle. The secondary function of the RON resistor is to create a nearly constant operating frequency over the input operating voltage range. If the output voltage of the regulator is changed by adjusting the feedback divider then it is generally required that the RON resistor value also be changed in order to maintain the same operating frequency. Cout A parallel connection of a 1uF 50V and a 100uF 6.3V multilayer ceramic are used for the output capacitor. Locations are provided on the PCB assembly for experimenting with additional output capacitors. Some recommended values are shown on the schematic as “DNS” and labeled in the PCB silkscreen as “OPT”. CinA 10 uF 50V multilayer ceramic is connected as the input filter. Locations are provided on the PCB assembly for experimenting with additional input capacitors. Some recommended values are shown on the schematic as “DNS” and labeled in the PCB silkscreen as “OPT”. Performance Characteristics Efficiency 24V Input@ 25°C Dissipation, 24V Input@ 25°C 30114404 30114405 Line and Load Regulation @ 25°C Transient Response 24VIN 3.3Vo 0.6A to 3A Step 30114407 30114406 www.national.com 4 AN-2032 Notes 5 www.national.com LMZ14203 3A Demo Board SIMPLE SWITCHER® Power Module Quick Start Guide 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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