LM5050MK-2

LM5050-2EVAL Evaluation Board LM5050-2EVAL Evaluation Board National Semiconductor Application Note 2051 Donald P. Jones November 1, 2010 Introduction The LM5050-2 evaluation board is designed to demonstrate the capabilities of the LM5050-2 OR-ing Diode Controller. It is intended for evaluation of the functions of the LM5050-2. One high side N-channel power MOSFET is used. The LM5050-2 evaluation board schematic is shown in Figure 5 . The evaluation board is designed to highlight applications with a small solution size. For more information about the LM5050-2 functional and electrical characteristics, refer to the LM5050-2 datasheet. Operating Range • Minimum Input Voltage, 6V • Maximum Input Voltage, 50V • Output Current Range: 0A to 15A • Ambient Temperature Range 0°C to 50°C • Board Size 1.50 inches x 2.25 inches To aid in the demonstration and evaluation of high-side ORing diode controller solution based on the LM5050-2. The load current capability is limited at 15A by the ratings of the terminals and the PCB copper area and weight. The PCB layout has not been tested for currents above 15A, so this should only be done with some degree of caution. The maximum input voltage is limited by the breakdown voltage rating of both D1 and D2. Typical evaluation board performance and characteristics curves are shown in through . The PCB layout is shown in and . Test points are provided for optional control and signal monitoring. 30121312 FIGURE 1. Forward Waveforms Evaluation Board Start-Up Before applying power to the LM5050-2 evaluation board, all external connections should be verified. The external power supply must be turned off and connected with proper polarity to the VIN, VOUT, and GND terminals. Under basic evaluation conditions the nPGD, VLOGIC, and Off test points are left open. The evaluation board will be in the normal operating mode when power is applied. The Off terminal is used only when there is a desire to disable normal operation and invoke the MOSFET test comparator. 30121313 FIGURE 2. Reverse Waveforms AN-2051 © 2010 National Semiconductor Corporation 301213 www.national.com AN-2051 Inductive Kick-Back Protection Diode D1 and capacitor C1 serve as inductive kick-back protection to limit negative transient voltage spikes generated on the input when the input supply voltage is abruptly taken to zero volts. Diode D2 and capacitor C2 serve as inductive kick-back protection to limit positive transient voltage spikes generated on the output when the input supply voltage is abruptly taken to zero volts. through the body diode and the voltage difference between the IN pin and the OUT pin will be greater than the VDS(TST) threshold of typically 350 mV. In this case the nFGD pin will go to a low impedance stage and the nPGD test point voltage will be at a logic low.. If the MOSFET is shorted, the voltage difference between the IN pin and the OUT pin will be less than the VDS(TST) threshold of typically 350 mV. In this case the nFGD pin will remain in a high impedance state and the nPGD test point voltage will remain at a logic high. Off Test Point The Off test point provided on the LM5050-2 evaluation board is used to control the LM5050-2 operation. The Off test point is connected directly to the LM5050-2 OFF pin. See the LM5050 datasheet for more details. To enable the LM5050-2 apply a voltage less than 0.8V to the Off test point, connect the Off test point to GND, or leave the Off test point open (default). If the Off test point is left open, the LM5050-2 OFF pin internal pull-down will ensure that the LM5050-2 becomes operational. To disable the LM5050-2 apply a voltage greater than 2.0V to the Off test point. VLOGIC Test Point An external voltage is applied to the VLOGIC test point so that the logical output of the Status test point can be evaluated. The VLOGIC pin is connected to the LM5050-2 nFGD pin through a 10 kΩ pull-up resistor. The voltage applied to the VLOGIC test point should be between 3.0V and 5.5V. 30121316 FIGURE 3. MOSFET Test, No Fault There are several factors that may prevent the nFGD pin from going to a logic low in an otherwise good application. If there is a redundant, parallel, supply in operation, that supply may hold the OUT pin voltage close enough to the IN pin voltage that the VDS(TST) threshold is not exceeded. Additionally, a high output capacitance value, or a low load current, may require that a significant amount of time be allowed for the output capacitance to discharge to the point where the VDS (TST) threshold is exceeded and the nFGD pin goes low. Status (nPGD) Test Point The nPGD test point is wired directly to the LM5050-2 opendrain nFGD pin (device pin 1), with pull-up bias from the VLOGIC test point through a 10 kΩ pull-up resistor. While the Off test point is low, or open, the nFGD pin will be in a high impedance state and the nPGD test point voltage will be at a logic high. When the Off test point is high, the MOSFET Gate drive is OFF. If the MOSFET is normal, current will begin flowing www.national.com 2 AN-2051 30121303 FIGURE 4. Connection Diagram 30121304 FIGURE 5. Schematic Diagram 30121307 FIGURE 6. Component Placement 3 www.national.com AN-2051 30121305 FIGURE 7. Evaluation Board, Top Side (Component) 30121306 FIGURE 8. Evaluation Board, Bottom Side www.national.com 4 AN-2051 Bill of Materials ID U1 C1 C2 C3 D1 Description IC; Ideal OR-ing Diode Controller Capacitor: MLCC; 1.0µF; ±10%; 100V; X7R; 1825 Capacitor: 22 µF; ±20%; 100V; Aluminum Electrolytic; SMT Not Installed Diode: Schottky Barrier Rectifier; 1A: 60V; SMA Diode: TVS; Unidirectional; 600W; 60V; SMB MOSFET: N-Channel; 100V; 40A; 0.025Ω; D2PAK Not Installed Resistor: 10.0 kΩ; 0.10W; ±1%; 100ppm; Thick Film; 0603 Terminal: 6-32 Screw; Vertical; Snap-In PCB Mount; 15A Manufacturer National Semiconductor Corporation Vishay/Vitramon Panasonic/ECG ON Semiconductor Micro Commercial Components Diodes Inc Vishay/Siliconix Vishay/Dale ROHM Semiconductor Mfgr Part Number LM5050MK-2 VJ1825Y105KBBAT4X EEE-HA2A220P SS16T3G SS16-TP SMBJ60A-13-F SUM40N10-30-E3 CRCW060310K0FKEA MCR03EZPFX1002 D2 Q1 R1 R2 VIN VOUT GND GND Off nPGD VLOGIC GND GND Keystone Electronics 7693 Test Point Terminal: 0.040in Dia Mtg Hole; White Keystone Electronics 5012 5 www.national.com LM5050-2EVAL Evaluation Board Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: www.national.com Products Amplifiers Audio Clock and Timing Data Converters Interface LVDS Power Management Switching Regulators LDOs LED Lighting Voltage References PowerWise® Solutions Temperature Sensors PLL/VCO www.national.com/amplifiers www.national.com/audio www.national.com/timing www.national.com/adc www.national.com/interface www.national.com/lvds www.national.com/power www.national.com/switchers www.national.com/ldo www.national.com/led www.national.com/vref www.national.com/powerwise WEBENCH® Tools App Notes Reference Designs Samples Eval Boards Packaging Green Compliance Distributors Quality and Reliability Feedback/Support Design Made Easy Design Support www.national.com/webench www.national.com/appnotes www.national.com/refdesigns www.national.com/samples www.national.com/evalboards www.national.com/packaging www.national.com/quality/green www.national.com/contacts www.national.com/quality www.national.com/feedback www.national.com/easy www.national.com/solutions www.national.com/milaero www.national.com/solarmagic www.national.com/training Applications & Markets Mil/Aero PowerWise® Design University Serial Digital Interface (SDI) www.national.com/sdi www.national.com/wireless www.national.com/tempsensors SolarMagic™ THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. 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