AN1260 Li-Ion/Li-Poly Battery Charge and System Load Sharing Management Design Guide With MCP73871 Author: is available. To prevent overcharging Li-Ion batteries, an elapse timer is usually required as a secondary method to turn off the battery charge activities, before a proper termination condition is met. Minimum current detection during the Constant Voltage (CV) stage is the typical termination method for Li-Ion batteries. If a system is constantly drawing current out of a Li-Ion battery, the charge management system will never be terminated properly by minimum current. It can turn on and off periodically, or result in an error by a timer-fault condition. Brian Chu Microchip Technology Inc. INTRODUCTION The rechargeable Li-Ion/Li-Poly batteries are widely used in today’s portable Consumer Electronics (CE). Commonly seen Li-Poly batteries are Li-Ion Polymer batteries that use a solid polymer separator and share the same charge algorithm with Li-Ion batteries. Thus, Li-Ion batteries will represent both Li-Ion and Li-Poly batteries in this application note. Because of the growing features and the increasing size of the display in a portable electronic product, the battery usage is also modifying. The daily battery charging frequency increases, and it becomes important to operate a device while charging its battery. Microchip’s MCP73871 was developed to overcome these design challenges of Li-Ion battery-powered applications. The MCP73871 is a monolithic solution that offers compact size and rich features. It is an ideal candidate to design in small form-factor systems, while extending the system runtimes and battery life. This application note is intended to offer detailed design guidance for portable electronics designers who are interested in taking advantage of using Microchip’s MCP73871 in their projects. The MCP73871 demonstrates strategies to deliver Li-Ion charge management solutions in a short time, satisfying space and cost concerns. The traditional method to design a battery-powered system is to connect the system load directly on the battery. The system load continuously discharges the Li-Ion battery and costs a battery’s life cycle. In order to maximize the life cycle of Li-Ion batteries, it is recommended to terminate the charge properly and power the system from the input power supply, when it AC-DC Adapter or USB Port 18, 19 470Ω 6 10 μF IN PG 470Ω 7 330 kΩ OUT STAT2 470Ω 8 STAT1 LBO 2 3 Low High 110 kΩ Low High Low High Low High FIGURE 1: 4 9 17 OUT 1, 20 System Load 4.7 μF 14, 15, 16 VBAT VBAT_SENSE 4.7 μF 5 THERM NTC Single-Cell Li-Ion Battery VPCC SEL PROG2 PROG1 TE PROG3 CE 13 RPROG1 12 10 kΩ RPROG3 VSS 10,11(EP) Typical MCP73871 Application. 2009-2011 Microchip Technology Inc. DS01260B-page 1 AN1260 MCP73871 DEVICE DESCRIPTION The MCP73871 device is a fully integrated linear solution for system load sharing and Li-Ion/Li-Polymer battery charge management, with AC-DC wall adapter and USB port power sources selection. It is also capable of autonomous power source selection between input or battery. Along with its small physical size, the low number of required external components makes the device ideally suited for portable applications. The MCP73871 device automatically obtains power for the system load from a single-cell Li-Ion battery or an input power source (AC-DC wall adapter or USB port). The MCP73871 device specifically adheres to the current draw limits governed by the USB specification. With an AC-DC wall adapter providing power to the system, an external resistor sets the magnitude of 1A maximum charge current, while supporting up to 1.8A total current for the system load and battery charge current. EXAMPLE OF BATTERY CHARGER AND SYSTEM LOAD SHARING DESIGN SPECIFICATIONS The example system that will be applied in this application note requires an average of 100 mA load current, and consumes a maximum of 500 mA peak current for a short duration of time. A 950 mAh rated Li-Ion battery is used to operate the example system. The system continuously operates while charging the Li-Ion battery. The input power supply supplies the system load and charges the battery when a battery is present in the system. When the input power source is removed, the system is supported by the battery. When the system load and the battery charge current requires more energy than the supply current can afford, the system load has higher priority than the battery charger. Note: The MCP73871 device employs a Constant Current/ Constant Voltage (CC/CV) charge algorithm with a selectable charge termination point. The constant voltage regulation is fixed with four available options: 4.10V, 4.20V, 4.35V, or 4.40V to accommodate the new, emerging battery charging requirements. The MCP73871 device also limits the charge current based on die temperature during high-power or high-ambient conditions. This thermal regulation optimizes the charge cycle time, while maintaining the device reliability. The MCP73871 device includes a low-battery indicator, a power-good indicator and two charge status indicators that allows for outputs with LEDs or communication with host microcontrollers. The MCP73871 device is fully specified over the ambient temperature range of -40°C to +85°C. This application note shows how to design a simple system load sharing and battery management system with Microchip’s popular MCP73871 for cost-sensitive applications. For more in-depth documentation on these subjects please refer to Section “References”. Note: The above information is available in the MCP73871 data sheet (DS22090). DS01260B-page 2 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 at the back of this document. Technical support is available through the web site at: http://www.microchip.com/ support. The information in this application note is for reference only. Product design and production are the customer’s responsibilities. LI-ION/LI-POLYMER BATTERIES Important attributes when selecting a battery are: • • • • • Internal Resistance Operational Load Current Energy Density (Size and Weight) Charge/Discharge Cycles (Life Cycle) Capacity (dominates the operational duration without external power source present) As with most engineering work, these key attributes do not coincide with a reasonable cost. There is always a trade-off between them when selecting the battery chemistry for a portable application. Please refer to Microchip’s AN1088 – “Selecting the Right Battery System for Cost-Sensitive Portable Applications While Maintaining Excellent Quality” for the details of battery chemistry comparisons.  2009-2011 Microchip Technology Inc. AN1260 Li-Polymer batteries are also recognized as Li-Ion Polymer batteries. Li-Polymer can be charged with the same algorithm as Li-Ion batteries. The flexible formfactors, such as high energy density in weight (about 200 Wh/kg) and volume (about 400 Wh/kg), and a relatively low profile to fit inside the compact applications, make them ideal candidates for portable products. Note: A protection circuit is required for Li-Ion batteries to prevent overvoltage during the charge cycle, and under voltage during the discharge cycle; overcurrent as well in both directions. Batteries usually take a considerable amount of space and weight in today’s portable devices. The energy density for each chemistry dominates the size and weight for the battery pack. Li-Ion has advantages in both energy density weight and energy density volume among other available battery technologies. Wide Range Input Buck Converter MCP73871 OUT PIN Boost Converter Buck/Boost Converter LDO FIGURE 2: Typical DC-DC Voltage Converter Examples. Note: When operating with single cell Li-Ion batteries, output voltage range can be from 3.0V-4.2V. It is recommended not to operate at minimum battery voltage, to prolong a Li-Ion battery’s life. Please refer to the battery manufacturer’s data sheet or design guide for details. MCP73871 DESIGN GUIDE Power Supply Input (IN) The integrated system load sharing and the power path management features of the MCP73871 simplify the design and reduce the circuit board space. Unlike low-cost Li-Ion battery charge management solutions, the MCP73871 requires additional planning ahead when designing a system around it. This section will offer a detailed design guidance to develop a Li-Ion battery powered system. The MCP73871 can use a regular wall wart or a USB port from computers as its primary power supply. When using a regulated wall wart, the proper input voltage range must be between VBAT + 300 mV and 6V. The rated supply current of the wall wart has to meet the system requirement. Keep in mind that the MCP73871 device only supports up to 1.8A combined current for the system load and the charge current of a Li-Ion battery. When supplying from a USB port, the MCP73871 submits to the current limits governed by the USB specification. System Output Terminal (OUT) The MCP73871 powers a device from system output terminals, pin 1 and pin 20. There is no fixed voltage regulation to the system from the device. Therefore, proper DC-DC converters might be required for system design. A designer has to carefully review specifications when developing a new product. The OUT is supported by either input power supply or a single cell Li-Ion battery. The available typical system load is 1.65A, while the minimum is 1.5A from a wall wart power supply. A system designer should always consider the worst condition. Please refer to page 5 of the MCP73871 Data Sheet (DS22090) for details. Typical voltage converters are included, but not limited to buck, boost, buck/boost and LDO. • Buck Converter – Step down to proper voltage level • Boost Converter – Step up to proper voltage level • Buck/Boost Converter – Step down and up depends on the input source and output requirement • LDO – Low dropout voltage regulator for step down only 2009-2011 Microchip Technology Inc. INPUT CURRENT LIMIT CONTROL (ICLC) Input Current Limit Control (ICLC) prevents the system and charger from overdrawing the available current from power sources. When the system demands more current than the input power supply can provide, or the input ICLC is reached, the switch will become forward biased, and the battery is able to supplement the input current to the system load. The ICLC sustains the system load as its highest priority. This is done by reducing the non-critical charge current, while adhering to the current limits governed by the USB specification, or the maximum AC-DC adapter current supported. Further demand from the system is supported by the battery, if possible. Selectable USB Port Input Current: • Low: 1 Unit Load/High: 5 Unit Loads Note: Each unit load is of 100 mA. A device should not draw more than the specified unit of loads. DS01260B-page 3 AN1260 Fast Charge Current Set (PROG1) 700 600 Current (mA) 500 400 Input Current Battery Current Load Current 300 200 100 0 Ideal Diode -100 -200 0 Fast Charge Current Set (PROG1) determines the maximum constant current with a resistor tie from pin 13 to the ground (VSS). PROG1 also sets the maximum allowed charge current and the termination current set point (10% of fast charge current). The programming resistance for desired charge current can be calculated using the following equation: EQUATION 1: 100 200 300 400 500 600 700 1000V I CHAREG = -------------------R PROG1 Load Current (mA) FIGURE 3: Control. USBHigh - Input Current Limit Figure 3 illustrates the function of ICLC when USBHIGH is selected. RESISTOR VS. CURRENT Where: RPROG1 = kilo-ohms (kΩ IREG = milli-ampere (mA The Input Source Type Selection (SEL) pin is used to select the input power source for the input current limit control feature. With logic-level high, the MCP73871 allows maximum current of 1800 mA from a typical wall wart. With logic-level low, the MCP73871 assumes that a USB port input power source is selected. For example, a fast charge current that equals 760 mA is calculated to meet the design specification for a 950 mAh rated battery at 0.8C. A 750 mA fast charge current is selected to simplify the design process. A 1.3 kΩ resistor is chosen to allow a 750 mA fast charge current. A 750 mA precondition current, 10% of fast charge current, is applied to the Li-Ion battery when VBAT is below the preconditioning cut-off voltage. USB Port Current Set (PROG2) EQUATION 2: Input Source Type Selection (SEL) The USB Port Current Regulation Set input (PROG2) is a digital input selection. A logic-low limits a 1-unit load input current from the low-power port (100 mA); a logichigh limits a 5-unit load input current from the highpower port (500 mA). Unlike many monolithic battery charge management controllers that set the charge current for USB port operations, the PROG2 of MCP73871 sets input current limits for both system load and battery charge current, which ensures that no overcurrent is drawn from the USB ports. Note: The overcurrent protection circuit that ensures proper operations and the safety of USB ports should be implemented at the host and self-powered hubs. The MCP73871 serves as secondary overcurrent protection from USB port only. CHARGE CURRENT 950mA 0.8 = 760mA Note: EQUATION 3: Select IREG = 750 mA SELECT RESISTOR 1000V RPROG1 = ----------------- = 1.3k 750mA EQUATION 4: When: FAST CHARGE SEL = High IFastCh arg e = ISupply – I SystemLoad When: SEL = Low ;PROG2 = High I FastCh arg e = 500mA – ISystemLoad When: SEL = Low ;PROG2 = Low I FastCh arg e = 100mA – ISystemLoad The supply current has to be sufficient for the system load current and fast charge current. Otherwise, the system load current has priority over fast charge current. DS01260B-page 4 2009-2011 Microchip Technology Inc. AN1260 Termination Current Set (PROG3) The charge cycle is terminated when, during the Constant Voltage mode, the average charge current diminishes below a threshold established with the value of a resistor connected from PROG3 to VSS or the internal timer has expired. The charge current is latched off and the MCP73871 enters a Charge Complete mode. EQUATION 5: Note: If the VPCC function is not required in a system, the VPCC pin can simply connect to VIN. The resistors are selected at a hundred kohm range, to minimize the supply current from the voltage divider. VIN RESISTOR VS. CURRENT 1000V I TERMINATION = -------------------R PROG3 330 kΩ Where: RPROG3 = kilo-ohms (kΩ ITERMINATION = milli-ampere (mA VPCC The termination current is the same for inputs, from either the USB port or the AC-DC adapter, and needs to be less than the charge current set to ensure system function properly. Voltage Proportional Charge Control (VPCC) Voltage Proportional Charge Control (VPCC) is a key feature of MCP73871 that allows the output to maintain the proper voltage level, even when the input varies. Equation 6 demonstrates how to calculate the proper value for VPCC. When the VPCC voltage drops below 1.23V, it triggers the dynamic function of MCP73871 to maintain the proper output voltage level, with support from the Li-Ion battery. Equation 6 assumes the required input voltage of 5V. The resistor selection is flexible. Figure 4 depicts the connection of the voltage divider that supplies proper voltage for the VPCC pin. The divider is based on the calculation of Equation 6. However, if the input drops below UVLO, the Li-Ion battery will become the primary power source. EQUATION 6: VPCC DIVIDER R2 V VPCC = ------------------- VIN = 1.23V R 1 + R2 110 kΩ FIGURE 4: VPCC Divider. Battery Temperature Monitor (THERM) The MCP73871 continuously monitors the battery temperature during a charge cycle by measuring the voltage between the THERM and VSS pins. An internal 50 μA current source provides the bias for a typical 10 kΩ negative-temperature coefficient thermistor (NTC). The MCP73871 compares the voltage at the THERM pin to the factory-set thresholds of 1.23V and 0.25V, typically. Once a voltage outside the thresholds is detected during a charge cycle, the MCP73871 immediately suspends the charge cycle. The charge cycle resumes when the voltage at the THERM pin returns to the normal range. The charge temperature window can be set by placing fixed value resistors in series-parallel with a thermistor. The resistance values of RT1 and RT2 can be calculated with the following equations, in order to set the temperature window of interest. Assume: R 2 = 110k 110k 1.23V = ------------------------------ 5V 110k + R 1 R1 = 337.2k R1 = 330 kΩ is selected 2009-2011 Microchip Technology Inc. DS01260B-page 5 AN1260 EQUATION 7: NTC Charge Enable (CE) RT2 RCOLD 24k = RT1 + --------------------------------RT2 + R COLD With the CE input low, the Li-Ion battery charger feature of the MCP73871 will be disabled. The charger feature is enabled when CE is active-high. Allowing the CE pin to float during the charge cycle may cause system instability. The CE input is compatible with 1.8V logic. RT2 RHOT 5k = RT1 + -----------------------------RT2 + R HOT Where: Charge Status Outputs (STAT1, STAT2) RT1 is the fixed series resistance RT2 is the fixed parallel resistance RCOLD is the thermistor resistance at the lower temperature of interest RHOT is the thermistor resistance at the upper temperature of interest THERM RT1 10 kΩ NTC RT2 STAT1 and STAT2 are open-drain logic outputs for connection to LEDs that are used for charge status indication. Alternatively, a pull-up resistor can be applied for interfacing to a host microcontroller. The Low Battery Output (LBO) indicator shares the same output pin with STAT1. It reminds the system or the end user when the Li-Ion battery level is low. The LBO feature is enabled when the system is running from the LiIon batteries. The LBO indicator can be used as an indication to the user via a lit up LED, or to the system via a pull-up resistor, when interfacing to a host microcontroller that an input source, other than the battery, is supplying power. When using a low battery output indicator, the STAT1 pin needs to connect to a working voltage source, other than VIN. Power Good (PG) FIGURE 5: Resistor Connection. Battery Charge Control Output (VBAT) and Battery Voltage Sense (VBAT_SENSE) Connect to the positive terminal of Li-Ion batteries for restoring energy back to the batteries. It is recommended to apply a ceramic capacitor with low Equivalent Series Resistance (ESR) and Equivalent Series Inductance (ESL) to ensure loop stability when the battery is disconnected. A precision internal voltage sense regulates the final voltage on this VBATTERY_VOLTAGE_SENSE to the positive terminal of a Li-Ion battery. Timer Enable (TE) The Timer Enable (TE) input option is used to enable or disable the internal timer. A low signal on this pin enables the internal timer and a high signal disables the internal timer. The TE input can be used to disable the timer when the system load is substantially limiting the available supply current to charge the battery. The TE input is compatible with 1.8V logic. Note: The Power Good (PG) is an open-drain logic output for the input power supply indication. The PG output is low whenever the input to the MCP73871 is above the UVLO threshold and greater than the battery voltage. The PG output can be used as an indication to the user via a lit up LED, or to the system via a pull-up resistor, when interfacing to a host microcontroller that an input source, other than the battery, is supplying power. Table 1 depicts the status outputs of MCP73871 in various conditions. TABLE 1: STATUS OUTPUTS STATE STAT1 STAT2 Shutdown PG High Z High Z Preconditioning L High Z L Constant Current L High Z L L High Z L High Z L L Constant Voltage Charge Complete - Standby High Z Temperature Fault L L L Timer Fault L L L High Z Low Battery Output L High Z No Battery Present High Z High Z L No Input Power Present High Z High Z High Z The built-in safety timer is available for the following options: 4 HR, 6 HR and 8 HR. DS01260B-page 6 2009-2011 Microchip Technology Inc. AN1260 Design Specifications/Requirement • Input Voltage Range: - 2A rated 5V +/- 5% AC-DC adapter - 950 mAh Li-Ion battery (3.6V Nominal) • Constant Charge Current: - 1C (Please refer to the recommended value from selected battery manufacturer) • Constant Charge Voltage: 4.2V • Precondition Current: - 0.1C or recommend value (Please refer to the recommended value from selected battery manufacturer) • Termination Current - 0.07C (Please refer to the recommended value from selected battery manufacturer) • Low battery warning • Safety Timer: Turn charger off after 6 hours before termination. Note: “C” Rate Definition: The theoretical capacity of a battery is determined by the amount of active materials in the battery. It is expressed as the total quantity of electricity involved in the electrochemical reaction, and is defined in terms of coulombs or ampere-hours. EQUATION 8: SELECT RESISTOR 1000V R PROG1 = ----------------- = 1.05k 950mA TESTING CONDITIONS: - Battery Open Voltage: 3.8V (Both Charge and Discharge) - Battery Capacity: 950 mAh - Battery Charge Voltage: 4.2V - Battery Nominal Voltage: 3.6V - Supply Voltage: 5.2V - Constant Current (Fast Charge): 950 mA - Minimum System Load: 100 mA - Maximum System Load: 520 mA 2009-2011 Microchip Technology Inc. DS01260B-page 7 AN1260 SUMMARY For input power management, the ICLC avoids the overcurrent drain from a restricted power source, such as a USB port. VPCC enables system load in maintaining proper voltage level when input power supply is insufficient. Depending on the power path conditions, the battery will either be in Help mode or primary power source. The MCP73871 also offers three standard status outputs, two statuses for battery management and one for power good. In addition to the standard status outputs, the low battery indicator is also available from the MCP73871. In order to minimize external components, there are many factory preset options to choose from. Please refer to the MCP73871 Data Sheet (DS22090) for additional information. IDISCHARGE = 520 mA BATTERY = 950 mAh 4.5 4.0 -0.1 -0.2 3.5 -0.3 3.0 -0.4 2.5 -0.5 2.0 1.5 Discharge Current (A) 0 5.0 Battery Voltage (V) System Voltage (V) The MCP73871 helps system designers simplify the design complexities and minimize the external component for portable devices. Integrated loadsharing and power path management allow seamless switching between system load and charge current in different conditions. The MCP73871 also offers an independent charge current and termination current settings through resistors and preset logic inputs. -0.6 0 10 20 30 40 Time (Minutes) FIGURE 7: Discharge Profile. The MCP73871 Evaluation Board, User’s Guide and Gerber File are available through Microchip’s web site: http://www.microchip.com. 1.2 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 1 0.8 0.6 0.4 ISYSTEM = 100 mA BATTERY = 950 mAh 0.2 Supply Current (A) Battery Voltage (V) System Voltage (V) Figure 6 and Figure 7 depict the example system with a typical 950 mAh rated Li-Ion battery. Figure 6 shows a typical charge profile with a continuous current at 100 mA from the system load and 950 mA fast charge current. Figure 7 shows a typical discharge profile of a continuous current at 520 mA. FIGURE 8: Board. MCP73871 Evaluation 0 0 10 20 30 40 50 60 Time (Minutes) FIGURE 6: Typical Charge Profile With 100 mA System Load. DS01260B-page 8 2009-2011 Microchip Technology Inc. AN1260 REFERENCES  MCP73871 Data Sheet, “Stand-Alone System Load Sharing and Li-Ion/Li-Polymer Battery Charge Management Controller”, Microchip Technology Inc., DS22090, ©2008.  “Lithium Batteries”, Gholam-Abbas Nazri and Gianfranco Pistoia Eds.; Kluwer Academic Publishers, ©2004.  “Handbook of Batteries, Third Edition”, David Linden, Thomas B. Reddy; McGraw Hill Inc., ©2002.  AN1149, “Designing A Li-Ion Battery Charger and Load Sharing System With Microchip’s Stand-Alone Li-Ion Battery Charge Management Controller”, Brian Chu; Microchip Technology Inc., DS01149, ©2008.  AN1088, “Selecting the Right Battery System for Cost-Sensitive Portable Applications. While Maintaining Excellent Quality”, Brian Chu; Microchip Technology Inc., DS01088, ©2007. 2009-2011 Microchip Technology Inc. DS01260B-page 9 AN1260 NOTES: DS01260B-page 10 2009-2011 Microchip Technology Inc. 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. It is your responsibility to ensure that your application meets with your specifications. MICROCHIP MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND WHETHER EXPRESS OR IMPLIED, WRITTEN OR ORAL, STATUTORY OR OTHERWISE, RELATED TO THE INFORMATION, INCLUDING BUT NOT LIMITED TO ITS CONDITION, QUALITY, PERFORMANCE, MERCHANTABILITY OR FITNESS FOR PURPOSE. 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. No licenses are conveyed, implicitly or otherwise, under any Microchip intellectual property rights. Trademarks The Microchip name and logo, the Microchip logo, dsPIC, KEELOQ, KEELOQ logo, MPLAB, PIC, PICmicro, PICSTART, PIC32 logo, rfPIC and UNI/O are registered trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. FilterLab, Hampshire, HI-TECH C, Linear Active Thermistor, MXDEV, MXLAB, SEEVAL and The Embedded Control Solutions Company are registered trademarks of Microchip Technology Incorporated in the U.S.A. Analog-for-the-Digital Age, Application Maestro, chipKIT, chipKIT logo, CodeGuard, dsPICDEM, dsPICDEM.net, dsPICworks, dsSPEAK, ECAN, ECONOMONITOR, FanSense, HI-TIDE, In-Circuit Serial Programming, ICSP, Mindi, MiWi, MPASM, MPLAB Certified logo, MPLIB, MPLINK, mTouch, Omniscient Code Generation, PICC, PICC-18, PICDEM, PICDEM.net, PICkit, PICtail, REAL ICE, rfLAB, Select Mode, Total Endurance, TSHARC, UniWinDriver, WiperLock 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. All other trademarks mentioned herein are property of their respective companies. © 2009-2011, Microchip Technology Incorporated, Printed in the U.S.A., All Rights Reserved. Printed on recycled paper. ISBN: 978-1-61341-274-9 Microchip received ISO/TS-16949:2002 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. 2009-2011 Microchip Technology Inc. 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