LM25056EVAL/NOPB

Texas Instruments Application Note 2144 Joseph Wu January 16, 2012 Introduction PCB Features The LM25056EVK evaluation kit provides the design engineer with a telemetry measurement IC board with a PMBus™ compliant SMBus™/I2C interface. This application note describes the various functions of the board, how to test and evaluate it, and how to use the companion graphical user interface (GUI). The GUI is used to collect telemetry, configure warning and fault thresholds, and assist the designer with selection of external components for a specific application. Use of the advanced telemetry and monitoring capabilities of this device requires the installation of the Intelligent Power Manager graphical user interface. Please check the LM25056 webpage for the latest software and datasheet information. • • • • • Input voltage range: 3V to 15V (limited by input clamp D1) Programmable Current Measurement Range: 7.5 Amps or 15 Amps Computer connection to communications dongle, through USB cable PCB Size: 3.5” x 3.5” Solution Size: 0.75” x 0.75” LM25056 Evaluation Board LM25056 Evaluation Board Simplified Schematic 30160361 FIGURE 1. Simplified Evaluation Board Schematic © 2012 Texas Instruments Incorporated 301603 SNVA613 be measured with VAUX, and a DIODE bypass to disable the temperature measurement. Test points are provided to measure the input voltage, output voltage, VDD, VREF, the sense resistor voltage (through RS+ and RS-), and the temperature DIODE. Other test points can be used to apply voltage to ENABLE and VDDX pins. www.ti.com AN-2144 The simplified schematic for the LM25056 evaluation board is shown in Figure 1. Connections to the PMBus interface are provided by J1. Panduit® terminal lugs bolt down to the PCB to provide input and output connections. Jumpers ADR0, ADR1, and ADR2 set the PMBus address of the device to one of 27 unique addresses. Jumpers also exist to connect ENABLE to an external VDD supply, VIN to a voltage divider to AN-2144 lated and is provided to accommodate evaluation of designs for measuring currents greater than 15A. For currents higher than 15A, it is recommended to use the copper Panduit® lugs with low gauge wire to minimize the cable power dissipation and voltage drops. The LM25056EVB is supplied with the PMBus address set to 16h as dictated by the jumper configuration of the ADR0, ADR1, and ADR2 jumper connections. Getting Started The LM25056 evaluation kit hardware is shown in Figure 2. The board offers two connections for the system input voltage and load. In the board's current form, the system voltage and load can be plugged directly into the female banana receptacles. To measure higher currents, the sense resistors can be paralleled or replaced to maintain the full-scale measurement voltage of the sense resistor. A footprint for RS2 is not popu- 30160333 FIGURE 2. Connection Illustration The first step to evaluate the telemetry features of LM25056 demonstration is to install the GUI software. The software is included on a CD in the evaluation kit and is titled PMBManager-x.x.x-xxxxxxxx.exe, where the x characters indicate the software version and build date. This file should be executed on a PC running Windows XP or later to install the software. Once the GUI software is installed the hardware should be configured as shown in Figure 2 which can exceed the absolute maximum rating of the LM25056, resulting in its destruction. To protect against such voltage transients, a transient voltage suppression (TVS) diode D1 is provided to clamp the voltage at the input to within safe operating limits. Device Evaluation After configuring the hardware connections, apply an input voltage of 12V to the device. The current hardware configuration allows the LM25056 device to work with 3V to 15V system rails; however, this getting started guide will assume an input voltage of 12V. Launch the GUI by going to the Windows Start menu -> All Programs -> PMBManager-x.xxxxx > PMBManager. A pulldown menu should come up with a list of possible devices that the PMBManager can run. Select the "LM25056" option as shown in Figure 3. Hardware Setup Steps 1. Connect the input supply to the VIN and GND banana plugs. 2. Connect the load to the VOUT and GND banana plugs. 3. Connect the FTDI Dongle to the 10 pin connector on the left side of the board. 4. Connect the supplied mini USB cable from the FTDI dongle to an USB port on a PC. When the FTDI dongle is connected for the first time the user will be prompted to install the device drivers. For the most current driver installation procedure refer to the README.TXT file in the installation directory. For testing the board functionality, a low inductance connection to the input supply is recommended. Its purpose is to minimize voltage transients which occur when the load current changes or is shut off. If not careful, wiring inductance in the supply lines will generate a voltage transient at shutoff www.ti.com 30160301 FIGURE 3. Device Selector 2 AN-2144 The device should be detected on the PMBus and the initial load screen should appear as shown in Figure 4. If a device is not detected, an option is provided to rescan, ignore, or exit the GUI. If the hardware is intended to be connected, check the USB connection to the PCB, FTDI connection to the evaluation module, and verify that the power is present on the evaluation PCB by measuring the voltage between the GND and VIN testpoints. Ignoring the detection message allows use of the integrated design tool without the hardware connected. 30160331 FIGURE 4. Initial GUI Screen 30160303 FIGURE 5. LM25056 Block Level Representation Click on the detected device ID (NSC-LM25056-AA) to display a block level representation of the device as shown in Figure 5. The block level view of the device provides a display of all the telemetry data as well as the faults and warnings supported by the device. The faults and warnings supported are generally associated with an invalid input or output condition. The warnings shown on the left side of the block representation are generally associated with the input. These include input under voltage (UV), input over voltage (OV), and input over power (OP). The SMBus alert status (SMBA) is also shown on the left side and will turn red during any warning or fault event. To facilitate the evaluation of the device, SMBus alerts are automatically cleared by the GUI. The warnings or faults shown on the right side of the block representation include input over current (OC), and over temperature (OT). The warnings shown at the bottom of the block representation are asscociated with the VAUX measurement. The VAUX undervoltage (UV) and the VAUX overvoltage (OV) indicators are shown next to the auxiliary measurement. To show a repetitive update of the device telemetry and status click on the play icon at the top of the screen. The play button starts an active telemetry log of the gathered data. Clicking the stop icon stops the telemetry collection and allows for the log file to be viewed and saved. The pause button pauses both the displaying and logging of telemetry information. To disable displaying undesired telemetry click the display icon on the block representation. This will open the window shown in Figure 6 that will allow the user to disable the undesired telemetry, fault, and warning information from appearing on the block level device representation. 30160338 FIGURE 6. LM25056 Telemetry Display Options 3 www.ti.com AN-2144 Note that turning off the various warning options does not mask the faults from issuing an SMBus alert - it just does not display them if they occur. The device is capable of masking various faults and this functionality can be setup in the device configuration panel. sired by left clicking on the event log window and dragging window with the mouse to the desired location. Plotting Telemetry To enable telemetry data plots click on the sine wave icon located on the LM25056 block representation. After enabling the telemetry, a prompt will appear requesting entry of the GUI sample rate, plot rate, and plot depth. For most cases the default rates and depths will be acceptable. The plotting tool allows the user to select the desired data to be plotted. Up to 2 different parameters may be plotted at the same time as shown in Figure 7. GUI Event Log A GUI event log is provided to keep track of GUI configuration changes and device fault events. To display the event log select View from the main menu bar and then View Event Log. The event log will appear in the bottom right of the main GUI window. The event log can be detached and expanded if de- 30160335 FIGURE 7. LM25056 GUI with Telemetry Plotting Tool Enabled Device telemetry data is plotted as a black line that continually updates as the device is queried. In addition to the device data the relevant warning and fault thresholds are also plotted. Warning thresholds are shown as orange lines while fault thresholds are shown in red. www.ti.com By going to the plot menu option the user can disable the plotting grid as well as the warning and fault lines. 4 AN-2144 Configuring the LM25056 Warning thresholds, temperature fault threshold, protection ranges, fault masking, and averaging can be configured in the Device Configuration panel. The first tab of this panel, shown in Figure 8, is enabled by clicking the gear icon shown on the LM25056 block representation. 30160360 FIGURE 9. Device Configuration Window - Fault Behavior Tab The Averaging tab allows the user to set the value of the MFR_SAMPLES_FOR_AVG register of the LM25056 and sets the number of samples averaged for telemetry of VIN, IIN, PIN and VAUX. This is selectable from 1 to 4096 in powers of 2. Detail of the Averaging tab is shown below in Figure 10. 30160336 FIGURE 8. Device Configuration Panel - Warning and Fault Thresholds Tab The Warning and Fault Threshold tab allows configuration of the input under voltage, input over voltage, output under voltage, input over current, input power, and over temperature warnings. This tab also allows adjustment of the over temperature fault threshold. Fault threshold for the current limit and power limit are set by the hardware design based on the sense resistor. Decimal values for the thresholds are shown in the text box located to the right of the slider bar. Above the decimal values setting is the value of the setting in hexadecimal; which can be useful when developing software for this device. The Fault Behavior tab shown in Figure 9 allows the user to set the device fault and warning configuration and masking. By selecting Fault Masking, it allows individual faults and warnings to be masked and not be shown as an SMBus alert. Faults and warnings that only issue a SMBus alert allow masking of the alert. 30160332 FIGURE 10. Device Configuration Window - Averaging Tab For convenience, the Device Configuration Panel can be undocked by holding down the left mouse button while the cursor is at the top of the panel and dragging it to where you would like it to be placed. 5 www.ti.com AN-2144 changed, the device hardware configuration needs to be updated in the design tool section. To open the design tool click the wrench icon located on the LM25056 block representation which will open the window displayed in Figure 11. GUI Design Page The GUI assumes the hardware configuration is set to default evaluation board configuration. If any of the components are 30160337 FIGURE 11. LM25056 GUI Design Tool Activating the design page pulls several adjustable inputs a typical applications schematic. Design inputs are keyed in on the left side of the window. The input voltage for the LM25056 runs from 3 to 17V. In this tool, it only shows the range for infomational purposes and is not used for calculation in the remainder of the window. The Maximum VAUX1 window is used to calculate the resistor divider for R1 and R2. The calculator assumes that the maximum measured value of the VAUX pin is 1.0V. In operation, the maximum measured value is near 1.2V and the difference allows for a buffer to the full scale. The tool also assumes that R2 is 10.0 kΩ and calculates the required R1 value. Once the Maximum VAUX1 value is entered, Values for R1 and R2 appear in the Component Results section. The Std. 1% Resistors checkbox will enter in the closest standard 1% values that are available to the resistors. The Maximum Load Current window is used to determine the size of the sense resistor needed based on the current sense range. The LM25056 has two current sense ranges. The GAIN=0 has an approximate current sense range of 30mV across the sense resistor and is the default state. The GAIN=1 sets the current sense range to approximately 60mV. The current sense range is set with the pull down window on the left side of the design tool. Once the Maximum Load Current and the Current Sense Range windows are set, the current sense resistor is set in the Current Sense Resistor and Component Results sections. As a default, a setting of 7.5A as the maximum load current at the current sense range of 30mV will set the current sense resistor RS to 4 mΩ. Entering these values will also show the www.ti.com power dissipation of RS in the Parametric Results section at the bottom of the design tool. The PMBus Slave Address pulldown window shows the possible PMBus addresses that the LM25056 can be set to respond to. By selecting the one of the 27 possible addresses, the necessary connection to the ADR0, ADR1, and ADR2 pins is shown on the circuit diagram. As an example, if 0x17 is selected, the ADR0 would be floating, ADR1 would be connected to VDD, and ADR2 would be grounded. This set of connections would be shown on the circuit diagram, and can be tested on the demo board. Once a design is complete the design should be saved by selecting the File menu, and then Save. Once the hardware is modified to match the design the GUI should be restarted and the hardware configuration file loaded right after the device is detected and placed. If the values in the design tool are different than the values on the board, erroneous telemetry and fault data will be reported by the GUI. To return to the block view of the device press the home icon located at the far left in the menu bar. The design tool is also useful to calculate the PMBus coefficients. With the correct value for current sense resistor (RS1) the tool will calculate the correct coefficients to scale the raw telemetry data. The coefficients can be viewed by selecting View from the main menu bar, and then selecting the PMBus Coefficient Editor. When the PMBus Coefficient Editor is opened, press the Get All button to show the currently used coefficients. If desired the equations used in the design tool can be calculated by hand using the equations provided in the datasheet. 6 tionality of the LM25056. These features include the ability to read telemetry, device identification and status registers, as well monitoring the SMBus Alert interrupt. GUI Register Page The GUI Register Page, as shown in Figure 12, provides the user with several features to help better understand the func- 30160362 FIGURE 12. LM25056 GUI Register Page Telemetry is updated by clicking the Update Telemetry button. This action will update the fields under the Averaged heading and under the Immediate heading along with PEAK PIN. Select which parameters to update by clicking in the box next to each parameter. If all parameter boxes under a given heading are checked, the Update will use the block read PMBus commands (AVG_BLOCK_READ and BLOCK_READ) to update the fields, ensuring that the readings are time aligned. If one or more of the boxes under the headings is not checked, the Update will use the respective individual read PMBus commands to make the telemetry readings and the measurements will not be time aligned. PEAK PIN is always read with discrete PMBus commands and, therefore, are never time aligned. The CLEAR_PIN_PEAK button is provided to clear the PEAK PIN reading which is often much higher than one would expect under steady state conditions. This is related to the large inrush current during power-on that gets 7 www.ti.com AN-2144 However, note the design tool calculates parameters factoring in worst case tolerances, while the equations in the datasheet based on typical thresholds. AN-2144 sampled by the internal power measurement circuitry and used to calculate PEAK PIN. The Identification Information can be obtained by clicking the Update ID Information button. The rest of this page is used to monitor and diagnose warning and fault conditions. The SMBA interrupt will indicate if a warning or fault has occurred and if the output voltage is within specifications. It is always active and there is no need to click an Update button to change their state. The LM25056 does not have a PGOOD indicator and is not used in this device. Clicking the Update Status button under the Register Operation Control heading will update the bits in all of the registers under the Status section as well as the telemetry in the BLACK_BOX_READ. Clicking the CLEAR_FAULTS will reset all warning and fault bits and issue an Update Status. If the warning and/or fault condition has been remedied, the bits will reset. If the warning and/or fault condition still exists, the registers will be updated within a millisecond and thus will appear to never have been cleared. The STATUS_WORD, STATUS_INPUT, STATUS_CML and DIAGNOSTIC_WORD registers operate in a cumulative way. That is, these registers display any and all warnings and errors that have occurred since the last CLEAR_FAULTS command was issued. The telemetry and DIAGNOSTIC_WORD that are part of the BLACK_BOX_READ are also updated by clicking the Update Status button. These telemetry parameters and bits are latched at the moment the SMBA signal was asserted. They are not reset or cleared by the CLEAR_FAULTS command but rather they are re-armed, or readied, to be over-written with new values at the onset of the next SMBA signal assertion. Note that these telemetry fields and this register are not cumulative. That is, they can only be updated once after the CLEAR_FAULTS command is issued, and it will be at the first occurrence of the SMBA assertion following the CLEAR_FAULTS. This allows the user to determine device conditions at the first occurrence of the SMBA assertion. External VDD The LM25056 VDD can be powered from an external source to maintain some telemetry readings if the VIN fails. On the evaluation board, a connection of VDDX to 5V can be used to power the VDD line and maintain telemetry readings for VIN and temperature. The VDDX supplies power through a Schottky diode and a large capacitor. Note that with an external VDD connected to the VDDX line, the LM25056 cannot be put into a low power mode with the ENABLE pin. In this case, simply connect the ENABLE to VDDX and lower this line down to disable the part. Board Layout and Probing Cautions Refer to the product datasheet for detailed layout guidelines. For most applications the layout of this evaluation module as detailed in the PC Board Layout section of this document should be sufficient to provide a working solution with accurate telemetry. The following should be kept in mind when the board is powered: 1. Use caution when probing the circuit to prevent injury as well as possible damage to the circuit. 2. At larger load current (>15A), the wire size and length used to connect the power source and the load may become very important. The wires connecting this evaluation board to the power source should be twisted together to minimize inductance in those leads. The same applies for the wires connecting this board to the load. This recommendation is made in order to minimize high voltage transients from occurring when the load current is shut off. 3. A 15V TVS diode located as close as possible to the LM25056 VIN and GND pins provides the critical function of clamping inevitable input voltage overshoots when the pass MOSFET turns off. 4. An analog signal ground plane is used local to the LM25056 and is connected to the PCB power ground planes at a single point. Shutdown With the circuit in normal operation, the LM25056 can be shutdown by grounding the ENABLE pin. www.ti.com 8 FIGURE 13. Evaluation Board Schematic 30160347 AN-2144 9 www.ti.com AN-2144 Bill of Materials Designator Value Description Manufacturer Part Number Qty. ADR0, ADR1, ADR2 1x3 Header, TH, 100mil, 1x3, Gold plated, 230 mil above insulator Samtec Inc. TSW-103-07-G-S 3 C1, C4 1000pF Ceramic, NPO, 50V, 10%, 0603 AVX 06035A102KAT2A 2 C2 0.1uF Ceramic, X7R, 25V, 10%, 0603 AVX 06033C104KAT2A 1 C3, CREF, CVDD 1uF Ceramic, X7R, 16V, 10%, 0603 Murata GRM188R71C105KA12D 3 C5 100uF Ceramic, X5R, 6.3V, 20%, 1210 Kemet C1210C107M9PACTU 1 D1 15V Diode TVS 15V 5kW SMC Littlefuse Inc. 5.0SMDJ15A 1 D2 30V, 0.2A Diode, Schottky, SOT-23 Diodes Inc. BAT54-7-F 1 GND2, GND3, GND4 Test Point, TH, Miniature, Black Keystone Electronics 5001 3 DIODE, ENABLE, VAUX1, VDD, VDDX, VS+, VS-, VREF Test Point, TH, Miniature, White Keystone Electronics 5002 8 VIN1, VOUT1, GND OUT, GND1 Terminal 90A Lug Panduit CB70-14-CY 4 H1, H2, H5, H6 Screw Machine, PHIL 4-40x1/4 SS B&F Fastener Supply NY PMS 440 0025 PH 4 H3, H4, H7, H8 Standoff, Hex, 4-40THR ALUM 1"L Keystone 2205 4 J1 Male Header, 5-Pin, Dual row, Right Angle Samtec, Inc. TSW-105-08-L-D-RA 1 J2 Female Header, 5-Pin, Dual row, Right Angle Sullins Connector Solutions PPPC052LJBN-RC 1 J3, J4, J5 Header, TH, 100mil, 1x2, Gold plated, 230 mil above insulator Samtec, Inc. TSW-102-07-G-S 3 QT1 40V, 0.2A NPN, SOT-323 Central Semiconductor CMPT3904 1 R1 150k RES, 150k ohm, 1%, 0.1W, 0603 Vishay-Dale CRCW0603150KFKEA 1 R2 10.0k RES, 10.0k ohm, 1%, 0.1W, 0603 Vishay-Dale CRCW060310K0FKEA 1 R4, R5, Rvs 0 RES, 0 ohm, 1%, 0.1W, 0603 Vishay-Dale CRCW06030000Z0EA 3 Test Point, TH, Miniature, Red Keystone Electronics 5000 4 RS+, RS-, VIN_TP, VOUT_TP RES, 0.004 ohm, 1%, 3W, 3921 Vishay-Dale WSL39214L000FEA 1 Shunt RS1 Shunt LP w/ Handle 2 Pos 30AU, Black TE Connectivity 881545-2 4 Banana Jack HDWR Banana Jack Uninsulated Pomona Electronics 3267 4 System Power Managment IC Vishay-Dale LM25056APSQ 1 U1 www.ti.com 0.004 Ohm LLP-24 10 AN-2144 PC Board Layout 30160342 Board Top Layer 30160343 Board Mid Layer 1 11 www.ti.com AN-2144 30160344 Board Mid Layer 2 30160345 Board Bottom Layer (viewed from top) www.ti.com 12 AN-2144 Notes 13 www.ti.com AN-2144 LM25056 Evaluation Board Notes www.ti.com 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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