MCP19111 PMBus™ Protocol-Enabled Point-of-Load (POL) Converter Reference Design User’s Guide 2015 Microchip Technology Inc. DS50002379A Note the following details of the code protection feature on Microchip devices: • Microchip products meet the specification contained in their particular Microchip Data Sheet. • Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the intended manner and under normal conditions. • There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Data Sheets. Most likely, the person doing so is engaged in theft of intellectual property. • Microchip is willing to work with the customer who is concerned about the integrity of their code. • Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not mean that we are guaranteeing the product as “unbreakable.” Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our products. Attempts to break Microchip’s code protection feature may be a violation of the Digital Millennium Copyright Act. If such acts allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act. Information contained in this publication regarding device applications and the like is provided only for your convenience and may be superseded by updates. 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Trademarks The Microchip name and logo, the Microchip logo, dsPIC, FlashFlex, flexPWR, JukeBlox, KEELOQ, KEELOQ logo, Kleer, LANCheck, MediaLB, MOST, MOST logo, MPLAB, OptoLyzer, PIC, PICSTART, PIC32 logo, RightTouch, SpyNIC, SST, SST Logo, SuperFlash and UNI/O are registered trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. The Embedded Control Solutions Company and mTouch are registered trademarks of Microchip Technology Incorporated in the U.S.A. Analog-for-the-Digital Age, BodyCom, chipKIT, chipKIT logo, CodeGuard, dsPICDEM, dsPICDEM.net, ECAN, In-Circuit Serial Programming, ICSP, Inter-Chip Connectivity, KleerNet, KleerNet logo, MiWi, MPASM, MPF, MPLAB Certified logo, MPLIB, MPLINK, MultiTRAK, NetDetach, Omniscient Code Generation, PICDEM, PICDEM.net, PICtail, RightTouch logo, REAL ICE, SQI, Serial Quad I/O, Total Endurance, TSHARC, USBCheck, VariSense, ViewSpan, WiperLock, Wireless DNA, and ZENA are trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. SQTP is a service mark of Microchip Technology Incorporated in the U.S.A. Silicon Storage Technology is a registered trademark of Microchip Technology Inc. in other countries. GestIC is a registered trademarks of Microchip Technology Germany II GmbH & Co. KG, a subsidiary of Microchip Technology Inc., in other countries. All other trademarks mentioned herein are property of their respective companies. © 2015, Microchip Technology Incorporated, Printed in the U.S.A., All Rights Reserved. ISBN: 978-1-63277-476-7 QUALITY MANAGEMENT SYSTEM CERTIFIED BY DNV == ISO/TS 16949 == DS50002379A-page 2 Microchip received ISO/TS-16949:2009 certification for its worldwide headquarters, design and wafer fabrication facilities in Chandler and Tempe, Arizona; Gresham, Oregon and design centers in California and India. The Company’s quality system processes and procedures are for its PIC® MCUs and dsPIC® DSCs, KEELOQ® code hopping devices, Serial EEPROMs, microperipherals, nonvolatile memory and analog products. In addition, Microchip’s quality system for the design and manufacture of development systems is ISO 9001:2000 certified. 2015 Microchip Technology Inc. Object of Declaration: MCP19111 PMBus™ Protocol-Enabled POL Converter Reference Design 2015 Microchip Technology Inc. DS50002379A-page 3 MCP19111 PMBus™ Protocol-Enabled POL Converter Reference Design NOTES: DS50002379A-page 4 2015 Microchip Technology Inc. MCP19111 PMBus™ PROTOCOL-ENABLED POL CONVERTER REFERENCE DESIGN USER’S GUIDE Table of Contents Preface ........................................................................................................................... 7 Introduction............................................................................................................ 7 Document Layout .................................................................................................. 8 Conventions Used in this Guide ............................................................................ 9 Warranty Registration.......................................................................................... 10 Recommended Reading...................................................................................... 10 The Microchip Web Site ...................................................................................... 10 Development Systems Customer Change Notification Service .......................... 11 Customer Support ............................................................................................... 11 MCP19111 PMBus™-Enabled POL Converter Reference Design License........ 11 Revision History .................................................................................................. 11 Chapter 1. Product Overview 1.1 Introduction ................................................................................................... 13 1.2 MCP19111 Device Short Overview .............................................................. 13 1.3 What is the MCP19111 PMBus™ Protocol-Enabled Point-of-Load Converter Reference Design? ................................................................ 15 1.4 System Requirements .................................................................................. 15 1.4.1 The Development System’s Components ................................................. 16 1.5 What the MCP19111 PMBus™ Protocol-Enabled Point-of-Load Converter Reference Design Kit Contains? ............................................................ 16 Chapter 2. Installation and Operation 2.1 Board Features ............................................................................................. 17 2.2 Getting Started ............................................................................................. 18 2.2.1 Necessary Instruments and Tools ............................................................. 18 2.2.2 Setup Procedure ....................................................................................... 18 2.2.3 Board Testing ............................................................................................ 19 Chapter 3. Calibration Procedure 3.1 Introduction ................................................................................................... 21 3.2 Voltage Calibration ....................................................................................... 22 3.3 Current Calibration with Inductor Temperature Measurement ..................... 23 Chapter 4. Typical Performance Data, Curves and Waveforms .............................. 25 2015 Microchip Technology Inc. DS50002379A-page 5 MCP19111 PMBus™ Protocol-Enabled POL Converter Reference Design Appendix A. Schematics and Layouts A.1 Introduction .................................................................................................. 33 A.2 Board – Schematic 1 .................................................................................... 34 A.3 Board – Schematic 2 .................................................................................... 35 A.4 Board – Top Layer ....................................................................................... 36 A.5 Board – Top Copper .................................................................................... 36 A.6 Board – Mid Layer 1 ..................................................................................... 37 A.7 Board – Mid Layer 2 ..................................................................................... 37 A.8 Board – Bottom Layer .................................................................................. 38 A.9 Board – Bottom Copper ............................................................................... 38 Appendix B. Bill of Materials (BOM) ...........................................................................39 Appendix C. Calibration Example C.1 Introduction .................................................................................................. 41 C.2 Configuration Requirements ........................................................................ 42 C.2.1 Calibration .................................................................................................42 Worldwide Sales and Service .....................................................................................44 DS50002379A-page 6 2015 Microchip Technology Inc. MCP19111 PMBus™ PROTOCOL-ENABLED POL CONVERTER REFERENCE DESIGN USER’S GUIDE Preface NOTICE TO CUSTOMERS All documentation becomes dated, and this manual is no exception. Microchip tools and documentation are constantly evolving to meet customer needs, so some actual dialogs and/or tool descriptions may differ from those in this document. Please refer to our web site (www.microchip.com) to obtain the latest documentation available. Documents are identified with a “DS” number. This number is located on the bottom of each page, in front of the page number. The numbering convention for the DS number is “DSXXXXXXXXA”, where “XXXXXXXX” is the document number and “A” is the revision level of the document. For the most up-to-date information on development tools, see the MPLAB® IDE online help. Select the Help menu, and then Topics to open a list of available online help files. INTRODUCTION This chapter contains general information that will be useful to know before using the MCP19111 PMBus™ Protocol-Enabled Point-of-Load Converter Reference Design. Items discussed in this chapter include: • • • • • • • • Document Layout Conventions Used in this Guide Warranty Registration Recommended Reading The Microchip Web Site Development Systems Customer Change Notification Service Customer Support Revision History I WARNING The present reference design is intended to be used only to prove the MCP19111 functionality and performance, solely in a laboratory environment. Microchip Technology Inc. assumes no liability for any damage resulting from using the present reference design in other purposes. 2015 Microchip Technology Inc. DS50002379A-page 7 MCP19111 PMBus™ Protocol-Enabled POL Converter Reference Design DOCUMENT LAYOUT This document describes how to use the MCP19111 PMBus™ Protocol-Enabled Point-of-Load Converter Reference Design as a development tool to emulate and debug firmware on a target board, as well as how to program devices. The document is organized as follows: • Chapter 1. “Product Overview” – Important information about the MCP19111 PMBus™ Protocol-Enabled Point-of-Load Converter Reference Design. • Chapter 2. “Installation and Operation” – Includes instructions on how to get started using the MCP19111 PMBus™ Protocol-Enabled Point-of-Load Converter Reference Design. • Chapter 3. “Calibration Procedure” – Includes instructions on the calibration procedure of the MCP19111 PMBus™ Protocol-Enabled Point-of-Load Converter Reference Design. • Chapter 4. “Typical Performance Data, Curves and Waveforms” – Includes typical performance graphs of data, curves and waveforms. • Appendix A. “Schematics and Layouts” – Shows the schematic and layout diagrams for the MCP19111 PMBus™ Protocol-Enabled Point-of-Load Converter Reference Design. • Appendix B. “Bill of Materials (BOM)” – Lists the parts used to build the MCP19111 PMBus™ Protocol-Enabled Point-of-Load Converter Reference Design. • Appendix C. “Calibration Example” – Gives an example of a calibration procedure for the MCP19111 PMBus™ Protocol-Enabled Point-of-Load Converter Reference Design. DS50002379A-page 8 2015 Microchip Technology Inc. Preface CONVENTIONS USED IN THIS GUIDE This manual uses the following documentation conventions: DOCUMENTATION CONVENTIONS Description Arial font: Italic characters Initial caps Quotes Underlined, italic text with right angle bracket Bold characters N‘Rnnnn Text in angle brackets < > Courier New font: Plain Courier New Represents Referenced books Emphasized text A window A dialog A menu selection A field name in a window or dialog A menu path MPLAB® IDE User’s Guide ...is the only compiler... the Output window the Settings dialog select Enable Programmer “Save project before build” A dialog button A tab A number in verilog format, where N is the total number of digits, R is the radix and n is a digit. A key on the keyboard Click OK Click the Power tab 4‘b0010, 2‘hF1 Italic Courier New Sample source code Filenames File paths Keywords Command-line options Bit values Constants A variable argument Square brackets [ ] Optional arguments Curly brackets and pipe character: { | } Ellipses... Choice of mutually exclusive arguments; an OR selection Replaces repeated text Represents code supplied by user 2015 Microchip Technology Inc. Examples File>Save Press <Enter>, <F1> #define START autoexec.bat c:\mcc18\h _asm, _endasm, static -Opa+, -Opa0, 1 0xFF, ‘A’ file.o, where file can be any valid filename mcc18 [options] file [options] errorlevel {0|1} var_name [, var_name...] void main (void) { ... } DS50002379A-page 9 MCP19111 PMBus™ Protocol-Enabled POL Converter Reference Design WARRANTY REGISTRATION Please complete the enclosed Warranty Registration Card and mail it promptly. Sending in the Warranty Registration Card entitles users to receive new product updates. Interim software releases are available at the Microchip web site. RECOMMENDED READING This user’s guide describes how to use MCP19111 PMBus™ Protocol-Enabled Point-of-Load Converter Reference Design. Other useful documents are listed below. The following Microchip documents are available and recommended as supplemental reference resources. MCP19110/11 Data Sheet (DS20002331) This data sheet describes the operation and features of the MCP19110/11 digitally-enhanced power analog controller with integrated synchronous driver. PMBus™ Monitoring Graphical User Interface User’s Guide (DS50002380) This user’s guide describes how to use the PMBus Monitoring Graphical User Interface (GUI). TB3139, MCP19111 PMBus™ Firmware Technical Brief (DS90003139) This technical brief describes how to use the MCP19111 PMBus firmware. THE MICROCHIP WEB SITE Microchip provides online support via our web site at www.microchip.com. This web site is used as a means to make files and information easily available to customers. Accessible by using your favorite Internet browser, the web site contains the following information: • Product Support – Data sheets and errata, application notes and sample programs, design resources, user’s guides and hardware support documents, latest software releases and archived software • General Technical Support – Frequently Asked Questions (FAQs), technical support requests, online discussion groups, Microchip consultant program member listing • Business of Microchip – Product selector and ordering guides, latest Microchip press releases, listing of seminars and events, listings of Microchip sales offices, distributors and factory representatives DS50002379A-page 10 2015 Microchip Technology Inc. Preface DEVELOPMENT SYSTEMS CUSTOMER CHANGE NOTIFICATION SERVICE Microchip’s customer notification service helps keep customers current on Microchip products. Subscribers will receive e-mail notification whenever there are changes, updates, revisions or errata related to a specified product family or development tool of interest. To register, access the Microchip web site at www.microchip.com, click on Customer Change Notification and follow the registration instructions. The Development Systems product group categories are: • Compilers – The latest information on Microchip C compilers, assemblers, linkers and other language tools. These include all MPLAB® C compilers; all MPLAB assemblers (including MPASM™ Assembler); all MPLAB linkers (including MPLINK™ Object Linker); and all MPLAB librarians (including MPLIB™ Object Librarian). • Emulators – The latest information on Microchip in-circuit emulators.This includes the MPLAB REAL ICE™ and MPLAB ICE 2000 In-Circuit Emulators. • In-Circuit Debuggers – The latest information on the Microchip in-circuit debuggers. This includes MPLAB ICD 3 In-Circuit debugger and PICkit™ 3 Debug Express. • MPLAB® IDE – The latest information on Microchip MPLAB IDE, the Windows® Integrated Development Environment for development systems tools. This list is focused on the MPLAB IDE, MPLAB IDE Project Manager, MPLAB Editor and MPLAB SIM Simulator, as well as general editing and debugging features. • Programmers – The latest information on Microchip programmers. These include production programmers, such as MPLAB REAL ICE In-Circuit Emulator, MPLAB ICD 3 In-Circuit Debugger and MPLAB PM3 Device Programmer. CUSTOMER SUPPORT Users of Microchip products can receive assistance through several channels: • • • • Distributor or Representative Local Sales Office Field Application Engineer (FAE) Technical Support Customers should contact their distributor, representative or field application engineer (FAE) for support. Local sales offices are also available to help customers. A listing of sales offices and locations is included in the back of this document. Technical support is available through the web site at: http://www.microchip.com/support MCP19111 PMBUS-ENABLED POL CONVERTER REFERENCE DESIGN LICENSE Copyright © 2015 Microchip Technology Inc. All rights reserved. 1. License Grant. Microchip licenses to you the right to use this reference design and all related documentation (“Reference Design Materials”) for purposes of developing your application using Microchip products. You may not re-distribute Reference Design Materials to any third parties. 2. Warranty Disclaimer. Reference Design Materials are provided for your convenience only and may be superseded by updates. These materials will not be deemed to modify Microchip’s standard warranty for its products. It is your responsibility to: (1) ensure that the Reference Design Materials, and your use thereof, meet your requirements; and (2) test your application. 2015 Microchip Technology Inc. DS50002379A-page 11 MCP19111 PMBus™ Protocol-Enabled POL Converter Reference Design REFERENCE DESIGN MATERIALS ARE PROVIDED “AS IS” WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY, TITLE, NON-INFRINGEMENT AND FITNESS FOR A PARTICULAR PURPOSE. 3. Limit on Liability. IN NO EVENT WILL MICROCHIP BE LIABLE OR OBLIGATED UNDER CONTRACT, NEGLIGENCE, STRICT LIABILITY, CONTRIBUTION, BREACH OF WARRANTY, OR OTHER LEGAL EQUITABLE THEORY ANY DIRECT OR INDIRECT DAMAGES OR EXPENSES INCLUDING BUT NOT LIMITED TO ANY INCIDENTAL, SPECIAL, OR CONSEQUENTIAL DAMAGES, LOST PROFITS OR LOST DATA, COST OF PROCUREMENT OF SUBSTITUTE GOODS, TECHNOLOGY, SERVICES, ANY CLAIMS BY THIRD PARTIES (INCLUDING BUT NOT LIMITED TO ANY DEFENSE THEREOF), OR OTHER SIMILAR COSTS. MICROCHIP DISCLAIMS ALL LIABILITY ARISING FROM THIS INFORMATION AND ITS USE. USE OF MICROCHIP DEVICES IN LIFE SUPPORT AND/OR SAFETY APPLICATIONS IS ENTIRELY AT THE BUYER’S RISK, AND THE BUYER AGREES TO DEFEND, INDEMNIFY AND HOLD HARMLESS MICROCHIP FROM ANY AND ALL DAMAGES, CLAIMS, SUITS, OR EXPENSES RESULTING FROM SUCH USE. TO THE FULLEST EXTENT PERMITTED BY LAW, MICROCHIP’S LIABILITY IS CAPPED AT THE AMOUNT YOU PAID DIRECTLY TO MICROCHIP FOR THESE REFRENCE DESIGN MATERIALS. 4. Governing Law. THIS LICENSE WILL BE GOVERNED BY AND CONSTRUCTED UNDER THE LAWS OF THE STATE OF ARIZONA AND THE UNITED STATES WITHOUT REGARD TO CONFLICTS OF LAWS PROVISIONS. Licensee agrees that any disputes arising out of or related to this License, Software or Reference Design Materials will be brought in the courts of State of Arizona. The parties agree to waive their rights to a jury trial in actions relating to this License. REVISION HISTORY Revision A (June 2015) This is the initial release of this document. DS50002379A-page 12 2015 Microchip Technology Inc. MCP19111 PMBus™ PROTOCOL-ENABLED POL CONVERTER REFERENCE DESIGN USER’S GUIDE Chapter 1. Product Overview NOTICE TO CUSTOMERS The present reference design is intended to be used only to prove the MCP19111 functionality and performance, solely in laboratory environment. Microchip Technology Inc. assumes no liability for any damage resulting from using the present reference design in other purposes. 1.1 INTRODUCTION This chapter provides an overview of the MCP19111 PMBus™ Protocol-Enabled Point-of-Load Converter Reference Design and covers the following topics: • MCP19111 Device Short Overview • What is the MCP19111 PMBus™ Protocol-Enabled Point-of-Load Converter Reference Design? • What the MCP19111 PMBus™ Protocol-Enabled Point-of-Load Converter Reference Design Kit Contains? CAUTION All the functionalities described in this document are specific to the original firmware loaded in the MCP19111. Once the user software is loaded, the PMBus communication and board settings become the user’s responsibility. 1.2 MCP19111 DEVICE SHORT OVERVIEW The MCP19111 device is a highly integrated, mixed signal, Analog Pulse-Width Modulation (PWM) Current mode controller with an integrated microcontroller core for synchronous DC/DC step-down applications. Since the MCP19111 uses traditional analog control circuitry to regulate the output of the DC/DC converter, the integration of the PIC® microcontroller mid-range core is used to provide complete customization of the device operating parameters, start-up and shutdown profiles, protection levels and Fault handling procedures. The MCP19111 is designed to efficiently operate from a single, 4.5V to 32V supply. It features integrated synchronous drivers, a bootstrap device, internal linear regulator and 4000 words of nonvolatile memory, all in a space-saving, 28-pin 5 mm x 5 mm QFN package. PMBus™ or I2C™ can be used by a host to communicate with, or modify the operation of, the MCP19111. A subset of the commands contained in the “PMBus™ Power System Management Protocol Specification, Revision 1.1” are supported by the ARD00609 board. An internal 5V rail provides power to the PIC MCU and is also present on the VDD pin. It is recommended that a 1 μF capacitor be placed between VDD and PGND. The VDD pin may also be directly connected to the VDR pin or connected through a low-pass RC filter. The VDR pin provides power to the internal synchronous driver. 2015 Microchip Technology Inc. DS50002379A-page 13 GPA6 VIN GPB1 TRACK PGOOD CNTL ADDR1 ADDR0 SYNC SMBus™ Alert SCL SDA 2015 Microchip Technology Inc. ICDDAT MPLAB® X ICD Programmer ICDCLK MCLR FIGURE 1-1: MCP19111 Typical Application. GPA0 HDRV GPA2 BOOT GPB2 PHASE +VOUT GPA3 LDRV -VOUT GPB7 VDD GPB6 MCP19111 VDR GPA1 +ISEN GPA4 -ISEN GPA7 +VSEN GPB0 -VSEN GPB4 PGND GPB5 GND GPA5 MCP19111 PMBus™ Protocol-Enabled POL Converter Reference Design DS50002379A-page 14 VIN Product Overview 1.3 WHAT IS THE MCP19111 PMBus™ PROTOCOL-ENABLED POINT-OF-LOAD CONVERTER REFERENCE DESIGN? The MCP19111 PMBus™ Protocol-Enabled Point-of-Load Converter Reference Design demonstrates how the MCP19111 device operates in a synchronous buck topology over a wide input voltage and load range. Nearly all operational and control system parameters are programmable by utilizing the integrated PIC microcontroller. For precise measurements of the output current, a precision op amp (MCP6061) and an inductor temperature sensor (MCP9700) are provided. The output current may be measured and calibrated using an internal or external op amp. The temperature compensation may be performed by temperature measurement or by second order polynomial approximation. The PMBus Monitoring Graphical User Interface (GUI) can be used to program the functioning parameters and to check the operational status. To simplify the connection, a USB to PMBus converter is implemented on board, allowing a standard interface to any Windows® computer. Alternatively, the user can program the MCP19111 using self-developed firmware (see Section 1.4.1 “The Development System’s Components”), tailoring it to the application. The evaluation board contains headers for In-Circuit Serial Programming™ (ICSP™) as well as I2C and mini-USB communication, pull-up and pull-down resistor pads and test point pads on each GPIO pin, and a push button for system development. The MCP19111 PMBus™ Protocol-Enabled Point-of-Load Converter Reference Design is also intended to demonstrate an optimized Printed Circuit Board (PCB) layout that minimizes parasitics, while increasing efficiency and power density. Proper PCB layout is critical to achieve optimum MCP19111 operation, as well as power train efficiency and noise minimization. 1.4 SYSTEM REQUIREMENTS To operate the board, the following tools are required: • Microsoft® .NET Framework 4.5 or higher • PMBus Monitoring Graphical User Interface: This graphical user interface allows monitoring and changing input and output parameters for any device that has an incorporated PMBus™ protocol. For installation, operation and other system requirements, see the “PMBus™ Monitoring Graphical User Interface User’s Guide” (DS50002380). WARNING Any changes in the Settings tab from the Developer menu may result in system instability and/or permanent damage of the board, and is the user’s sole responsibility to take the necessary precautions. 2015 Microchip Technology Inc. DS50002379A-page 15 MCP19111 PMBus™ Protocol-Enabled POL Converter Reference Design 1.4.1 The Development System’s Components To redevelop the board firmware, the following may be required: • MCP19111 MPLAB® X IDE Graphical User Interface Plug-In: This graphical user interface simplifies the configuration of the MCP19111. It is user-installed and resides within the MPLAB X IDE. The “MCP19110/11/18/19 – Buck Power Supply Graphical User Interface User’s Guide” (DS50002113) describes the plug-in installation procedure, as well as how to use it. • MPLAB® X Integrated Development Environment (IDE): This is a complete software development environment that links the software and hardware development. This is a free tool, available from Microchip, that supports device configuration, advanced programming, as well as debug support. The GUI resides inside the MPLAB X IDE. • MPLAB® XC8 Compiler: The firmware described above is coded in C and thus requires a C compiler. C compilers are available for free from Microchip’s web site. • Configuration tools: - PICkit™ Serial Analyzer: This communication tool may be used to configure the evaluation board. The PICkit Serial Analyzer is recommended and is available for purchase on microchipDIRECT. - PICkit 3 In-Circuit Debugger/Programmer: A programming tool is required to reprogram the evaluation board. The PICkit 3 or MPLAB ICD 3 is recommended and they are available for purchase on microchipDIRECT. - Any other user-preferred I2C connection for further board development. To resume the original functionality of the ARD00609, the user can download the 00609_RevA1.hex file from Microchip’s web site and upload it in the MCP19111 using a PICkit 3 In-Circuit Debugger/Programmer. 1.5 WHAT THE MCP19111 PMBus™ PROTOCOL-ENABLED POINT-OF-LOAD CONVERTER REFERENCE DESIGN KIT CONTAINS? This MCP19111 PMBus™ Protocol-Enabled Point-of-Load Converter Reference Design kit includes the following items: • MCP19111 PMBus™ Protocol-Enabled Point-of-Load Converter Reference Design board (ARD00609) • Important Information Sheet DS50002379A-page 16 2015 Microchip Technology Inc. MCP19111 PMBus™ PROTOCOL-ENABLED POL CONVERTER REFERENCE DESIGN USER’S GUIDE Chapter 2. Installation and Operation 2.1 BOARD FEATURES The MCP19111 PMBus™ Protocol-Enabled Point-of-Load Converter Reference Design was developed to provide a compact, low-cost and highly efficient step-down conversion for low-to-medium output currents. The key features of this board include: • • • • • • • • • • • • • • • Input Voltage Range: 8V to 14V Output Voltage: 1.2V (can be adjusted by software from 0.1 to 3.6V) Maximum Output Current: 20A 88% Typical Efficiency at 1.2V/15A output and 12V input 500 kHz Switching Frequency (can be software adjusted from 100 kHz to 1.6 MHz) On-Board High-Performance Power MOSFET Transistors Overcurrent and Overtemperature Protection Status Report (including errors, input voltage, output voltage and current) via the PMBus Communication Protocol Precision Op Amp for Accurate Output Current Measurement Inductor Temperature Sensor Calibration of Output Voltage Calibration of Output Voltage and Output Current Measurements (via PMBus) Undervoltage Lockout (UVLO) with Programmable (via software) Thresholds Output Overvoltage, Undervoltage and Overcurrent Lockout, Programmable via Software For Advanced Users (use with caution): Control Loop Parameters and MOSFET’s Switching Dead Time can also be Adjusted by Software. 2015 Microchip Technology Inc. DS50002379A-page 17 MCP19111 PMBus™ Protocol-Enabled POL Converter Reference Design 2.2 GETTING STARTED The MCP19111 PMBus™ Protocol-Enabled Point-of-Load Converter Reference Design is fully assembled and tested to evaluate and demonstrate the MCP19111 capabilities. 2.2.1 • • • • • • • • Necessary Instruments and Tools Adjustable DC Power Supply with 0V-15V/5 ADC Range Output Capability Electronic Load with at least 25A Current Capability and Load Stepping Capability Digital Oscilloscope with a Minimum Bandwidth of 50 MHz Digital Voltmeter/Ammeter Optionally, a Network Analyzer/Bode Plot Analyzer for Control Loop Analyzing PC with PMBMonitor GUI Pre-Installed USB-A to mini-USB Cable Wires for Connections, Capable to Sustain High Currents: - 5A for the connection between the adjustable DC power supply and board - 20A for the connection between the board and the electronic load 2.2.2 Setup Procedure To power-up the MCP19111 PMBus™ Protocol-Enabled Point-of-Load Converter Reference Design, the following steps must be completed: 1. Connect the electronic load to the J2 connector of the demo board; the Positive (+) and Negative (–) connector pins are marked on the board silkscreen. 2. Connect the adjustable DC power supply to the J1 connector of the demo board; the Positive (+) and Negative (–) connector pins are marked on the board silkscreen. 3. Supply 12V from the adjustable power source. 4. Connect the test board to a PC with the PMBMonitor GUI pre-installed via a USB-A to mini-USB cable (J3 connector). 5. After powering up, press the push button, BT1, to turn on the output voltage. Alternatively, the output may be turned on from the PMBMonitor GUI ON button (under Status>Operation Panel). 6. The board is factory set to deliver 1.2V at 20A maximum, with the loop adjusted for optimum performance and current measurement performed via the auxiliary op amp. If different settings are desired, changes may be performed in several ways: - Via the PMBus to USB on-board interface – refer to the “PMBus™ Monitoring Graphical User Interface User’s Guide” (DS50002380) for details. - Via PMBus – the user must connect a PMBus master via the I2C interface of the board, connector J1. - By user-developed software that may be loaded into the MCP19111 J2 connector using PICkit™ 3 or another suitable programming tool. DS50002379A-page 18 2015 Microchip Technology Inc. Installation and Operation 2.2.3 Board Testing The typical testing setup is depicted in Figure 2-1. Table 2-1 shows all the available test points on the board. Table 2-2 describes the ICP/I2C communication pins’ function. PROG on the J2 connector is used with the PICkit 3 in-circuit programmer/debugger. The user can connect various instruments at the listed test points to evaluate the parameters of the converter. The typical performance data, curves and waveforms are presented in Chapter 4. “Typical Performance Data, Curves and Waveforms”. USB TP33 RD2 TP34 TP35 TP12 TP3 TP5 TP2 TP10 RC2 RC1 TP1 RD1 ICP/I2C TP4 J1 TP32 BT1 BODE PLOT ANALYZER TP31 TP14 A B TP30 TP18 J2 PROG TP41 V TP40 TP16 V ADJ DC PS + + TP17 FIGURE 2-1: LOAD Max 20A - Typical Test Setup. 2015 Microchip Technology Inc. DS50002379A-page 19 MCP19111 PMBus™ Protocol-Enabled POL Converter Reference Design TABLE 2-1: TEST POINT DESCRIPTION Test Point Name TP1 GPA0 Connects to GPA0 or Analog Test Output (Note 1) TP2 GPB1 Connects to GPB1 (Note 1) TP3 GPB7 By Default, used as Power-on Signal (connected to BT1) (Note 1) TP4 GPA1 Connects to GPA1 (Note 1) TP5 GPB2 By Default, used for Inductor Temperature Measurement (Note 1) TP10 GPB6 Connects to GPB6 (Note 1) TP12 GPB0/SDA TP14 GPA7/SCL TP16 VIN Input Voltage TP17, TP41 GND Power GND TP18 CH A Injection Point for Loop Measurement TP30, TP31, TP32, TP33, TP34, TP35 SGND Signal GND TP35 GPA3 By Default, used as External Current Measurement Input (Note 1) TP40 VOUT Output Voltage and Channel B Injection Point for Loop Measurement Note 1: Description Connects to GPB0/SDA (Note 1) Connects to GPA7/SCL (Note 1) For a detailed description of the port pin functions, see the “MCP19110/11 Data Sheet”. TABLE 2-2: Note: DS50002379A-page 20 ICP/I2C™ COMMUNICATION CONNECTOR J1 PINS Pin Number Description 1 Do not connect 2 Do not connect 3 GND 4 SCL 5 SDA 6 GND Communication over the USB interface uses the same I2C bus; normally, the user should not simultaneously connect the USB and the ICP/I2C interfaces. 2015 Microchip Technology Inc. MCP19111 PMBus™ PROTOCOL-ENABLED POL CONVERTER REFERENCE DESIGN USER’S GUIDE Chapter 3. Calibration Procedure 3.1 INTRODUCTION In order to increase the accuracy of the output voltage setting, output voltage measurement and output current reading, a calibration procedure must be performed. It is recommended to use the Microchip dedicated PMBMonitor GUI that can be downloaded from the board’s web page, as it performs all needed computations and greatly simplifies the procedures. For more information on the mathematical basis and implementation of the calibration procedures, refer to the Appendix C. “Calibration Example”. Figure 3-1 shows the PMBMonitor GUI Interface Calibration tab. It also identifies the main panels used in the calibration procedures described in this chapter. For more information on the Installation and Operation of the PMBMonitor GUI, refer to the “PMBus™ Monitoring Graphical User Interface User’s Guide” (DS50002380). Calibration Tab Developer Menu IOUT Settings Panel VOUT Settings Panel LOG Text Box STATUS Bar Code Label FIGURE 3-1: PMBMonitor GUI – Calibration Tab. 2015 Microchip Technology Inc. DS50002379A-page 21 MCP19111 PMBus™ Protocol-Enabled POL Converter Reference Design 3.2 VOLTAGE CALIBRATION Follow these steps to perform the voltage calibration procedure: 1. Select Developer from the PMBMonitor GUI main menu, then choose the Calibration tab. 2. In the VOUT Settings Panel, press the Read button. PMBus™ Transmitted Value Measured Value Input Field Reads VOUT from the Board Sends Data to Board FIGURE 3-2: VOUT Settings Panel Description. 3. On the board, measure with an accurate voltmeter the output voltage between the TP41 and TP40 test points. 4. Input the value obtained in Step 3 in the “Measured” field, then press the Send button to update the data on the board. 5. Verify that both the output voltage (measured with the voltmeter) and the PMBMonitor transmitted value that appears on the screen are correct. 6. Go to the Status menu, and in the Operation Panel, press the StoreALL button to keep the actual value after power-off. StoreALL Button FIGURE 3-3: DS50002379A-page 22 Status Menu – Operation Panel. 2015 Microchip Technology Inc. Calibration Procedure 3.3 CURRENT CALIBRATION WITH INDUCTOR TEMPERATURE MEASUREMENT 1. Select Developer from the PMBMonitor GUI main menu, then choose the Calibration tab. 2. Choose a low test current (except zero, for example, 1A) and write the value in the first “Current” field in the IOUT Settings Panel. Set this current on the external load as accurate as possible. Press the corresponding Read button. A value will appear in the corresponding “Voltage” field. Updates the Value of the Temperature Coefficient Input the Low Test Current Updateable Values after Pressing Calculate Button Input the High Test Current Updates the Current Calibration FIGURE 3-4: IOUT Settings Panel. 3. Choose a high test current (at best, the highest load current, for example, 17A), write the value in the second “Current” field and set this output current on the external load. Press the corresponding Read button. Write down the value that appears in the second “Voltage” field. 4. Press the Calculate button. The values in the “ADC(T0)”, “Coefficient-X1” and “Coefficient-X0” fields may update once the calculations are done. 5. Press Send from the bottom of the IOUT Settings Panel. WARNING Keep constant board temperature around ambient during Steps 2 to 5; therefore, all these measurements should be done as fast as possible and/or provide adequate cooling. 2015 Microchip Technology Inc. DS50002379A-page 23 MCP19111 PMBus™ Protocol-Enabled POL Converter Reference Design Steps 6-12 are used to calibrate the temperature coefficient. Note that these steps apply only when a different inductor and/or layout is used. 6. Write down the T0 value from the “ADC(T0)” field. 7. Maintain the high-current output and allow the board to heat up (70-80°C is the optimum). 8. Press the high-current corresponding Read button and the Calculate button to update the values. Remember the updated value of the second voltage. 9. Compute the difference between the high-current voltage obtained in Step 8 and the one written down (see Step 3). 10. Compute the difference between the T0 value updated on Step 8 and the one written down (see Step 6). 11. Compute as the voltage difference, divided by the last second voltage value, divided again by the T0 difference (see example in Equation C-5) ( Step 9:Step 8:Step 10). Multiply the value by 16384; write the rounded to next integer value of the result in the “ALPHA” field and press the corresponding Send button at the right. 12. Go to the Status menu, and in the Operation Panel, press the StoreALL button to preserve the actual value after power-off. DS50002379A-page 24 2015 Microchip Technology Inc. MCP19111 PMBus™ PROTOCOL-ENABLED POL CONVERTER REFERENCE DESIGN USER’S GUIDE Chapter 4. Typical Performance Data, Curves and Waveforms This chapter shows examples of the parameters used for converter and performance curves, and waveforms. TABLE 4-1: CONVERTER PARAMETERS Parameter Input Voltage Range (V) Value Comments 8-14 — Output Voltage (V) 1.2 ±2.5% Tolerance Maximum Output Current (A) 20 Steady-State Output Current Output Voltage Ripple (mV) <30 VIN = 12V, IOUT = 20A Input Voltage Ripple (mV) <400 VIN = 12V, IOUT = 20A <30 Step Load 5A to 15A Output Voltage Overshoot during Step Load (mV) Switching Frequency (kHz) Typical 570 kHz — 95 Efficiency (%) 90 85 80 75 70 Vin=8V VIN = 8V VIN = 12V Vin=12V 65 60 FIGURE 4-1: Vin=14V VIN = 14V 0 5 10 IOUT(A) 15 20 Efficiency. 2015 Microchip Technology Inc. DS50002379A-page 25 MCP19111 PMBus™ Protocol-Enabled POL Converter Reference Design 1.21 1.208 1.206 VOUT (V) 1.204 1.202 1.2 1.198 1.196 1.194 1.192 1.19 0 FIGURE 4-2: 5 IOUT(A) 10 15 20 Load Regulation (VIN = 12V). VOUT FIGURE 4-3: DS50002379A-page 26 Output Voltage Ripple/Noise (VIN = 12V, IOUT = 10A, BW = 20 MHz). 2015 Microchip Technology Inc. Typical Performance Data, Curves and Waveforms VIN FIGURE 4-4: Input Voltage Ripple/Noise (VIN = 12V, IOUT = 10A, BW = 20 MHz). SW HDRV LDRV FIGURE 4-5: SW, LDRV and HDRV Signals (VIN = 12V, IOUT = 15A, BW = 300 MHz). 2015 Microchip Technology Inc. DS50002379A-page 27 MCP19111 PMBus™ Protocol-Enabled POL Converter Reference Design HDRV LDRV FIGURE 4-6: LDRV and HDRV Signals (VIN = 12V, IOUT = 15A, BW = 300 MHz). HDRV LDRV FIGURE 4-7: DS50002379A-page 28 Dead-Time Rise (VIN = 12V, IOUT = 15A, BW = 300 MHz). 2015 Microchip Technology Inc. Typical Performance Data, Curves and Waveforms HDRV LDRV FIGURE 4-8: Dead-Time Fall (VIN = 12V, IOUT = 15A, BW = 300 MHz). SW FIGURE 4-9: The Body Diode Conduction Time (VIN = 12V, IOUT = 15A, BW = 300 MHz). 2015 Microchip Technology Inc. DS50002379A-page 29 MCP19111 PMBus™ Protocol-Enabled POL Converter Reference Design VOUT IOUT FIGURE 4-10: Step Load Rising Current (VIN = 12V). VOUT IOUT FIGURE 4-11: DS50002379A-page 30 Step Load Falling Current (VIN = 12V). 2015 Microchip Technology Inc. Typical Performance Data, Curves and Waveforms VOUT FIGURE 4-12: Soft Start. 2015 Microchip Technology Inc. DS50002379A-page 31 MCP19111 PMBus™ Protocol-Enabled POL Converter Reference Design NOTES: DS50002379A-page 32 2015 Microchip Technology Inc. MCP19111 PMBus™ PROTOCOL-ENABLED POL CONVERTER REFERENCE DESIGN USER’S GUIDE Appendix A. Schematics and Layouts A.1 INTRODUCTION This appendix contains the following schematics and layouts for the MCP19111 PMBus™ Protocol-Enabled Point-of-Load Converter Reference Design: • • • • • • • • Board – Schematic 1 Board – Schematic 2 Board – Top Layer Board – Top Copper Board – Mid Layer 1 Board – Mid Layer 2 Board – Bottom Layer Board – Bottom Copper 2015 Microchip Technology Inc. DS50002379A-page 33 BOARD – SCHEMATIC 1 VDD TP1 GPA0/AN0 10k R38 510k C34 4 -A VDD OUTA 5.1k 3 GND GPA1/AN1/CLKPIN R7 VDD DNP R9 +A U3 1 TP35 R35 GPA3/AN3 4.7k GND GND C33 4.7 nF R34 C35 510k 4.7 nF R37 47k 1k GND TP10 R39 GPB6 VDD +OPAMP 3 VSS 2 R33 R5 10k 10k 5 R36 5.1k GND R18 DNP GND TP30 TP31 TP32 TP33 VDD LED VBUS DD+ ID GND GND GND GND GND 0 LD1 RED USB Mini-B Female R12 R11 4.7K 4.7K GND C23 1 μF OUT GPA2/T0CKI/INT U2 0 LED GND 1 μF R42 R43 R24 4.7K 4.7K R25 VDD 1 2 3 4 5 6 GPA5/MCLR GPB4/AN6/ICSPDAT GPB5/AN7/ICSPCLK/ALT_CLKPIN 0 1 2 3 4 5 6 GND TP12 50V 100 0.1 μF C22 D+ D- R40 C36 4.7K MCP2221 14 VDD VSS 13 RA5 RA0/D+/ICSPDAT 12 RA4 RA1/D-/ICSPCLK 11 MCLR/VPP/RA3 VUSB3V3 10 RC5 RC0/ICSPDAT 9 RC4 RC1/ICSPCLK 8 RC3 RC2 TP34 GPB0/SDA 2015 Microchip Technology Inc. GPA4 1 2 3 4 5 6 7 VDD R22 GPB0/SDA GPA7/SCL GND UVDD VDD GPA2/T0CKI/INT GPA4 R26 820 TP14 VOUT 2 GND GPA7/SCL VDD J3 1 1 2 3 4 5 VDD R20 10k GND GND UVDD DD+ VDD TACT SPST GND -OPAMP R2 DNP GND BT1 TP4 VDD 0.1 μF 1 2 5 SHIELD 0 4 4.7 nF GPB1/AN4/EAPIN 10k R3 GPB7 C32 TP2 VDD R4 R6 TP3 R1 DNP GPB0/SDA GPA7/SCL VDD GND J1 GND J2 GND 1 VDD GND R41 2 1K 3 TEMP C37 0.1 μF U4 GND GND MCP19111 PMBus™ Protocol-Enabled POL Converter Reference Design DS50002379A-page 34 A.2 BOARD – SCHEMATIC 2 VIN TP16 J4 1 2 EDZ250/2 C7 C3 C4 C5 10 μF 10 μF 10 μF 10 μF TP17 GND MCP19111 4 GPB4/AN6/ICSPDAT 5 GPA3/AN3 6 GPA7/SCL 7 OUT 8 GPA5/MCLR 9 GPA4 10 GPB0/SDA 11 GPB7 12 VIN 13 0.1 μF 14 GPB1/AN4/EAPIN GPB4/AN6/ICSPDAT -VSEN GPA3/AN3 +VSEN GPA7/SCL + ISEN GPA6 -ISEN GPA5/MCLR GPB6 GPA4 VDD GPB0/SDA BOOT GPB7 HDRV GND PHASE VIN VDR PGND LDRV 27 TEMP GPB5/AN7/ICSPCLK/ALT_CLKPIN 26 GPB1/AN4/EAPIN 25 R28 24 C8 23 21 51 TP18 0.47 μF 22 GND R29 GPB6 20 220 C9 19 0.47 μF 18 R30 0 D G S 17 D 16 G 15 S EP C16 1 μF GPA2/AN2/T0CKI/INT 28 Q1 MCP87050 1 L1 VOUT TP40 2 TP19 0.47 μH/26A Q2 C14 MCP87018 1000 μF C12 C13 C10 C11 100 μF 100 μF 100 μF 100 μF 29 C15 GPB5/AN7/ICSPCLK/ALT_CLKPIN 1 + 3 GPA2/T0CKI/INT GPB2/AN5 GPA1/AN1/CLKPIN 2 2 GPA1/AN1/CLKPIN GPA0/AN0 -OPAMP U1 1 GPA0/AN0 +OPAMP 2015 Microchip Technology Inc. A.3 VDR TP20 VDD TP41 R32 GND GND GND GND C19 1 μF 2.2 μF GND GND GND GND DS50002379A-page 35 Schematics and Layouts 10 C18 MCP19111 PMBus™ Protocol-Enabled POL Converter Reference Design A.4 BOARD – TOP LAYER A.5 BOARD – TOP COPPER DS50002379A-page 36 2015 Microchip Technology Inc. Schematics and Layouts A.6 BOARD – MID LAYER 1 A.7 BOARD – MID LAYER 2 2015 Microchip Technology Inc. DS50002379A-page 37 MCP19111 PMBus™ Protocol-Enabled POL Converter Reference Design A.8 BOARD – BOTTOM LAYER A.9 BOARD – BOTTOM COPPER DS50002379A-page 38 2015 Microchip Technology Inc. MCP19111 PMBus™ PROTOCOL-ENABLED POL CONVERTER REFERENCE DESIGN USER’S GUIDE Appendix B. Bill of Materials (BOM) TABLE B-1: Qty BILL OF MATERIALS (BOM) Reference Description 1 BT1 Switch TACT, SPST, 24V, 50 mA, B3S-1100, SMD 4 C3, C4, C5, Cap. Ceramic, 10 µF, 25V, 20%, X5R, SMD, C7 1210 2 C8, C9 Manufacturer Part Number OMRON Corporation B3S-1100 Panasonic® – ECG ECJ-4YB1E106M Cap. Ceramic, 0.47 µF, 10V, 10%, X5R, 0603 TDK Corporation Electronics® C1608X5R1A474K080AA 4 C10, C11, C12, C13 Cap. Ceramic,100 µF, 6.3V, 20%, X5R, 1210 Murata 1 C14 Cap. Alum., 1000 µF, 6.3V, 20%, Radial Nichicon Corporation RL80J102MDN1KX 1 C19 Cap. Ceramic, 2.2 µF, 10V, 20%, X5R, 0805 TDK Corporation C2012X5R1A225M085AA 4 C15, C18, C22, C23 Cap. Ceramic, 1 µF, 16V, 10%, X7R, 0805 TDK Corporation C2012X7R1C105K125AA 4 C16, C34, C36, C37 Cap. Ceramic, 0.1 µF, 25V, 10%, X7R, 0603 TDK Corporation C1608X7R1E104K080AA 3 C32, C33, C35 Cap. Ceramic, 4700 pF, 25V, 5%, C0G, 0603 TDK Corporation C1608C0G1E472J080AA 2 J1, J2 Conn. Header, .100, Single, STR, 6 Pos Sullins Connector Solutions PEC06SAAN 1 J3 Conn., USB Mini-B Female, SMD, R/A Hirose Electric Co., Ltd. UX60-MB-5ST 1 J4 Terminal Block, 5.08 mm, 2 Pos, PCB On-Shore Technology, Inc. EDZ250/2 1 L1 Fixed IND, 470 nH, 26A, 0.72 m Wurth Elektronik 7443320047 1 LD1 LED CHIPLED, 633 nm, Red, 0805, SMD OSRAM Opto LS R976-NR-1 Semiconductors GmbH. 1 PCB Printed Circuit Board – MCP19111 PMBus™ Microchip Technology Inc. 04-10337 Protocol-Enabled Point-of-Load Converter Reference Design 1 Q1 High-Speed N-Channel Power MOSFET Microchip Technology Inc. MCP87050T-U/MF 1 Q2 High-Speed N-Channel Power MOSFET Microchip Technology Inc. MCP87018T-U/MF 4 R1, R2, R7, DO NOT POPULATE R18 4 R3, R30, R42, R43 5 Res., SMD, 0.0, Jumper, 1/10W — GRM32ER60J107ME20L — Vishay/Dale CRCW06030000Z0EA R4, R5, R6, Res., SMD, 10 k, 5%, 1/10W, 0603 R9, R20 Yageo Corporation RC0603JR-0710KP 6 R11, R12, R22, R24, R25, R35 Res., SMD, 4.7 k, 5%, 1/10W, 0603 Yageo Corporation RC0603JR-074K7P 1 R26 Res., SMD, 820, 5%, 1/10W, 0603 ROHM Semiconductor MCR03ERTJ821 1 R28 Res., SMD, 51, 1%, 1/10W, 0603 ROHM Semiconductor MCR03ERTF51R0 1 R29 Res., SMD, 220, 1%, 1/10W, 0603 ROHM Semiconductor MCR03ERTF2200 2015 Microchip Technology Inc. DS50002379A-page 39 MCP19111 PMBus™ Protocol-Enabled POL Converter Reference Design TABLE B-1: Qty BILL OF MATERIALS (BOM) Reference Description Manufacturer Part Number 1 R32 Res., SMD, 10, 1%, 1/10W, 0603 ROHM Semiconductor MCR03ERTF10R0 2 R33, R36 Res., SMD, 5.1 k, 1%, 1/10W, 0603 ROHM Semiconductor MCR03ERTF5101 2 R34, R38 Res., SMD, 510 k, 1%, 1/10W, 0603 ROHM Semiconductor MCR03ERTF5103 2 R37, R41 Res., SMD, 1 k, 1%, 1/10W, 0603 ROHM Semiconductor MCR03ERTF1001 1 R39 Res., SMD, 47 k, 1%, 1/10W, 0603 ROHM Semiconductor MCR03ERTF4702 1 R40 Res., SMD, 100, 1%, 1/10W, 0603 ROHM Semiconductor MCR03ERTF1000 2 TP19, T20 Terminal Screw PC Heavy Duty Keystone Electronics Corp. 8197 4 TP16, TP17, PC Test Point Compact SMT TP40, TP41 Keystone Electronics Corp. 5016 6 TP19, TP20, Test Point PC Multi-Purpose BLK TP30, TP31, TP32, TP33 Keystone Electronics Corp. 5011 1 U1 Digitally Enhanced Power Analog Controller with Integrated Synchronous Driver Microchip Technology Inc. MCP19111-E/MQ 1 U2 USB 2.0 to I2C™/UART Protocol Converter with GPIO Microchip Technology Inc. MCP2221- I/SL 1 U3 MCHP Analog Op Amp, 1-Ch, 1 MHz, MCP6001T-I/OT, SOT-23-5 Microchip Technology Inc. MCP6001T-I/OT 1 U4 Low-Power Linear Active Thermistor™ ICs Microchip Technology Inc. MCP9700AT-E/OT DS50002379A-page 40 2015 Microchip Technology Inc. MCP19111 PMBus™ PROTOCOL-ENABLED POL CONVERTER REFERENCE DESIGN USER’S GUIDE Appendix C. Calibration Example C.1 INTRODUCTION Current measurements on the MCP19111 PMBus™ Protocol-Enabled Point-of-Load Converter Reference Design are done by differentially sensing a voltage drop on the inductor. This voltage drop is proportional to the current and the copper resistance of the inductor wire. Since the board output current limit is very high, there is also significant thermal dissipation and the inductor will heat up. This modifies the copper wire DC resistance, and consequently, the voltage drop on the inductor, making the current readings higher than the real value. The following fundamental equation describes the variation of electrical resistance versus temperature: EQUATION C-1: R T = R T0 1 + T – T0 Where: R T0 T = = = = Inductor DC Resistance Reference Temperature Ambient Temperature Temperature Coefficient The current sense amplifier has an offset specifically used to preserve output linearity. The readings taken from the amplifier output will have the following form: EQUATION C-2: V = IR+C Where: I = Load current set on the electronic load R = Inductor DC resistance C = Amplifier offset For convenience, it is considered that the amplifier offset does not vary with temperature. The purpose is to compensate the value of the inductor voltage drop with temperature, so that, in the end, the value for the same current is obtained at room temperature. To properly measure the inductor temperature, an MCP9700 temperature sensor has been placed in close contact with the inductor. Based on Equation C-1, the value of the copper resistance is approximated at room temperature (T0). EQUATION C-3: I R T0 = I R 1 – T V T0 – C = V – C 1 – T If lower than 100 mV, the amplifier offset may also be ignored in the calculation of the temperature coefficient with no significant change in the final result. 2015 Microchip Technology Inc. DS50002379A-page 41 MCP19111 PMBus™ Protocol-Enabled POL Converter Reference Design C.2 CONFIGURATION REQUIREMENTS To properly calibrate the board current reading, the user needs the following tools: • 12V power supply • PMBMonitor GUI running on a PC connected to the board via USB • 20A capable electronic load C.2.1 Calibration To calibrate the MCP19111 PMBus™ Protocol-Enabled Point-of-Load Converter Reference Design, proceed to the following steps: FIGURE C-1: MCP19111 Calibration Values Example. 1. Connect the PC with the GUI installed to the board and power-up the board. Go to the Developer menu in the GUI and select the Calibration tab. 2. Set the low test current to 1A and write the value in the first “Current” field, in the IOUT Settings Panel. Set this current on the external load as accurate as possible. Press the corresponding Read button. In this calibration example, a voltage of 0.247V is obtained in the corresponding “Voltage” field. 3. Set the high test current to 17A, write the value in the second “Current” field and set this output current on the external load. Press the corresponding Read button. In this calibration example, the result is 3.063V. Write down the result. 4. Press the Calculate button to update values. Write down the “ADC(T0)” value. This value will later be used to compensate all current readings. The “ADC(T0)” value and the second voltage value must be read simultaneously. For this example, the measurement was taken at +27°C, resulting in a reading of 770 mV or 631 ADC units (4x10-bit samples summed together). WARNING Keep constant board temperature around ambient during Steps 2 to 4 to obtain accurate values. Use an external cooling device on the board to prevent heating while drawing 17A. DS50002379A-page 42 2015 Microchip Technology Inc. Calibration Example 5. Press Send from the bottom of the IOUT Settings Panel. The coefficients are used in a first-order polynomial to calculate the output current based on the readings from the current amplifier. These coefficients are calculated using the amplifier offset and the inductor resistance at room temperature. Before the next steps, stop the external cooling device and make sure the board heats up to around 70-80°C. Cover it up, if necessary. Ideally, a forced temperature enclosure should be used, but this can also be done on a laboratory bench. 6. Press the Read button on the 17A row and write down the result. For this example, the reading is 3.516V. Write this down. 7. Press the Calculate button again and write down the “ADC(T0)” value. For the calibration example, the final temperature is +70°C, resulting in a temperature reading of 1200 mV or 983 ADC units. This is the “T” value later used in the calculations. 8. Start the calculations. Even if the values are shown as 12-bit (4x10-bit) results, the internal calculations only use 10-bit values for temperature and voltage. Using a different resolution will affect the α calculation. Do the following calculations: - Divide the temperature ADC results by 4. - Round the results to the nearest integer if necessary. For calculating the voltage ADC units, use a 5V reference. Two temperature points and two voltages are required to calculate the temperature coefficient: EXAMPLE C-1: 27°C 0.770V 631 ADC (12-bit) 158 ADC (10-bit) 70°C 1.200V 931 ADC (12-bit) 246 ADC (10-bit) = 246 ADC – 156 ADC = 88 ADC 17A @ 27°C 17A @ 70°C V(T0) = 3.063 V(T) = 3.516V Use the simplest form of the equation: EQUATION C-4: V T0 = V T 1 – T 3.063 = 3.516 1 – 88 = 0.001464 Since all calculations are done using integer arithmetic, the temperature coefficient is scaled internally by 214 or 16384. EQUATION C-5: ALPHA = 0.001464 16384 = 23.98 9. In the “ALPHA” field from the IOUT Settings Panel, write the rounded value (24) and press the associated Send button. 10. Go to the Status menu and press the StoreALL button to save all of the calibration values. The calibration is now finished and the board should indicate the correct load current at any operating temperature. 2015 Microchip Technology Inc. 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