Page 1 of 13
`
`EDN Access -- 03.02.95 Smart- battery
`technology: power management's missing lin
`
`EDN Staff - March 02, 1995
`
`EDN logo
`
`Design Feature:March 2, 1995
`Smart- battery technology: power
`management's missing link
`
`Anne Watson Swager,
`Technical Editor
`
`You no longer need to view a battery as a power-generating element whose characteristics are
`beyond your knowledge and control. The technology now exists to provide batteries with varying
`degrees of smarts, forming a critical link between the battery and host equipment.
`
`A smart-battery-management philosophy and a surge of battery-management products now provide
`you with powerful means to optimize battery performance. Smart-battery technology produces
`accurate information about the state of a battery and enables optimum charge control. One
`implementation of this technology is a standardized smart battery that includes all the necessary
`electronics to monitor itself and communicate to its host (see box on pg 50, "What's a smart
`battery?"). However, you can also team up many available ICs and batteries to tailor the battery's
`level of intelligence to your particular system.
`
`The need for smart-battery technology stems from the introduction of new battery types, each with its
`own stringent requirements for charging. In many cases, battery manufacturers won't supply these
`batteries-nickel-metal hydride (NiMH) and lithium-ion (Li-ion) batteries in particular-without
`mandating the use of an approved charge-control scheme.
`
`NiMH batteries are more sensitive to overcharge than their NiCd relations. High heat resulting from a
`high-rate overcharge is most damaging to an NiMH battery's capacity and cycle life. Thus, fast
`charging an NiMH battery requires tight control of charging characteristics and accurate feedback
`about the state of the battery.
`
`http://www.embedded.com/print/4350382
`
`5/6/2015
`Apple Inc., et al.
`Exhibit 1018
`Apple Inc., et al. v. Global Touch Solutions, Inc.
`IPR2015-01174
`
`Exhibit 1018, Page 001
`
`

`

`Page 2 of 13
`
`Although not widely available, Li-ion batteries mandate tight battery management for safety purposes
`alone. Li-ion batteries are simply dangerous if not charged properly. As one manufacturer said,
`"without battery management, Li-ion batteries wouldn't exist in the marketplace."
`PICTURE 1
`
`One goal of an intelligent battery and battery-management system, which this example GUI
`illustrates, is to provide reliable data-charge condition and charge state-to the end user.
`Another important goal is to control charging to enhance battery life. (Courtesy of SystemSoft
`Corp)
`
`The concept and underlying technology of a smart battery is not new. In 1989, without much fanfare,
`Sanyo Energy USA introduced the SI101, a fast-charge control module for NiCd and NiMH batteries
`($6.89 for 10,000 of the modules, $2.93 for just the IC). The company has integrated the module into
`battery packs for a wide variety of OEM customers. Many top-tier computer manufacturers are on this
`list, and others have developed their own battery-management schemes and ICs.
`
`However, recent industry developments have put the spotlight on smart batteries and battery
`management. In an effort to standardize smart batteries and the way they communicate, Duracell and
`Intel introduced the System- Management Bus and Smart-Battery Data Specification last year. They
`hope their efforts, which included widespread industry input, will lead to a standard power-
`management bus for portable equipment and a standard smart-battery hardware configuration and data
`set (see box, "Smart-Battery and System-Management Bus Specifications"). The standards push is not
`without controversy (see box, "The debate over smart-battery standards," pg 59).
`
`This year, Duracell will introduce its smart-rechargeable batteries as the first products to comply with
`these specs. However, many companies have designed intelligent-battery schemes of their own and
`perfected the underlying technology necessary to bestow battery intelligence, such as gas-gauge and
`charge-control techniques (see box, "For free information..." pg 63). Since 1991, Benchmarq
`Microelectronics has designed six gas-gauge ICs. In addition to Sanyo's module, Energizer Power
`Systems and National Semiconductor have teamed to develop an intelligent-battery chip set. And
`Rayovac and Benchmarq Microelectronics have cooperated on the design of an IC to control charging
`of Rayovac's Renewal line of reusable alkaline batteries. Rayovac plans to offer a full rechargeable
`system comprising four AA cells, the bq2901 IC, and a wall-cube adaptor for an OEM price of less
`than $6.
`
`Finally, software vendors are getting involved. SystemSoft and Phoenix Technologies offer software
`that makes some of the battery data that an intelligent battery supplies available to a computer end
`user. The goal of such products is to let the user make changes in power-management software. The
`software would indicate what affect these changes would have on battery capacity.
`
`Smart-Battery and System-Management Bus Specifications
`The Smart-Battery Specification jointly developed by Intel and Duracell-with input
`and feedback from major computer OEMs and component suppliers-attempts to
`address the three major problems that batteries pose to equipment designers and end
`users. Batteries are unpredictable and, in their simplest form, have no knowledge of
`remaining operating time. Battery-powered equipment has difficulty determining if
`the battery can supply power for an additional load. And, you must tailor current
`
`http://www.embedded.com/print/4350382
`
`5/6/2015
`Exhibit 1018, Page 002
`
`

`

`Page 3 of 13
`
`Smart-Battery and System-Management Bus Specifications
`battery chargers to a specific battery chemistry.
`The ultimate smart battery would provide complete information on its state of
`charge; answer questions of remaining capacity, based on a certain discharge rate;
`control its own charge regime that may vary with battery chemistry; and provide
`information on its history, such as maximum temperature extremes and numbers of
`cycles.
`
`The Duracell/Intel specification attempts to provide this information according to
`each company's interests in the battery and portable-equipment marketplace.
`Duracell's interest in developing this specification is to standardize all types of
`rechargeable batteries. Intel's interest is to further the acceptance of its power-
`management bus, which they hope would further the use of portable computers.
`Although the companies tightly aimed the specification at the portable-computer
`industry, it is applicable to other portable products. Remember that the well-
`thought-out scheme they present is only one way to implement an intelligent battery
`system.
`
`The specification itself comprises two essential parts: one defines a two-wire power-
`management bus that can communicate with various components, including but not
`limited to batteries. Intel's Architecture Labs created this System-Management Bus,
`or SMBus. The second is the actual smart-battery data and charger specification that
`details the batteries' data set and charge-control schemes.
`
`The bidirectional SMBus lets you send any type of command with two wires that
`link all components. The bus's goal is to improve mobile systems by enabling better
`power-management software and hardware and providing more control over power-
`managed components. The SMBus uses the I2C-bus as its backbone and adds a
`software protocol (a definition of bus transfers, commands, etc) on top of I2C's
`physical electrical layer. The SMBus specifies certain voltages, such as logic-0 and
`-1 threshold voltages, more tightly.
`
`The SMBus has much in common with the Access.bus protocol because both are
`based on I2C. The manufacturer intended the SMBus to act as an internal bus for
`connecting nonremovable components (the battery is the only exception). The
`Access.bus is an external bus for Plug-and-Play capability for external peripheral
`devices. However, the Access.bus spec can accommodate SMBus devices. Thus, a
`single controller can handle both.
`
`The Smart-Battery Data Set
`
`The Smart-Battery Specification defines a smart battery as "a battery equipped with
`specialized hardware that provides present state, calculated, and predicted
`information to its SMBus host under software control." The Smart-Battery Data
`(SBD) specification defines the data that flows across the SMBus between a smart
`battery, SMBus host, smart-battery charger, and other devices. The SBD
`specification includes software definition, error-detection, and signaling; the smart-
`
`http://www.embedded.com/print/4350382
`
`5/6/2015
`Exhibit 1018, Page 003
`
`

`

`Page 4 of 13
`
`Smart-Battery and System-Management Bus Specifications
`battery data protocols; and the smart-battery data set of all messages between the
`host, smart battery, and smart-battery charger.
`
`The data set defines 34 values of battery information. These values include
`temperature, voltage, and current. The data set also includes computed and stored
`values, such as AtRateTimeToEmpty (the predicted remaining operating time if the
`battery is discharged at the AtRate), RunTimeToEmpty (the predicted remaining
`battery life at the present rate of discharge), AverageTimeToEmpty (a one-minute
`rolling average of the predicted remaining battery life), AverageTimeToFull (a one-
`minute rolling average of predicted time until the battery reaches full charge),
`RemainingCapacity (in units of either current or power), RelativeStateOfCharge
`(predicted remaining capacity as percent of full-charge capacity),
`FullChargeCapacity (predicted pack capacity when fully charged), and CycleCount
`(number of charge/discharge cycles of the battery).
`FIGURE AAs envisioned by Duracell and Intel in their Smart-Battery
`Specification, a typical single smart-battery system consists of a power supply,
`host, smart battery, and smart-battery charger. The last three communicate via
`the two-wire serial SMBus.
`Fig A shows a possible smart-battery implementation that consists of a single
`battery (the spec also allows extensions for multiple batteries), battery charger, and
`a host. As envisioned in the specification, the smart charger is independent of the
`battery, but under the battery's control. Also, to be compatible with multiple battery
`chemistries, the battery must have some control of the charge regime. Chargers that
`closely cooperate with the battery have two distinct advantages. First, they provide
`the battery with all the power it can handle without overcharging, and second, they
`can recognize and correctly charge batteries with different chemistries and voltages.
`
`Smart-battery chargers
`
`The smarts in a battery are basically for self-monitoring and communication. For
`controlled charging, the battery needs a smart charger listening to it. The battery
`knows how it must be charged, but the actual power generation is the job of the
`external charger. According to the specification, a smart-battery charger is "a battery
`charger that periodically communicates with a smart battery and alters its charging
`characteristics in response to information provided by the smart battery."
`
`At the very least, a smart battery has a charge-control algorithm, but a smart charger
`can also have algorithms. You can implement a simple system, one in which the
`battery simply communicates whether it wants to be turned on or off. Or, you can
`implement a more sophisticated system, one in which a charger is smart enough to
`control a specialized battery.
`
`To accommodate these possible schemes, the Smart-Battery Charger Specification
`defines three levels of chargers. Level-1 chargers can only interpret the battery's
`critical warning messages that indicate the system should no longer charge a battery.
`A level-1 charger can't adjust its output in response to requests from the battery or
`
`http://www.embedded.com/print/4350382
`
`5/6/2015
`Exhibit 1018, Page 004
`
`

`

`Page 5 of 13
`
`Smart-Battery and System-Management Bus Specifications
`host, thus, it is not chemistry independent.
`
`In addition to supporting level-1 commands, a level-2 charger is an SMBus slave
`device that responds to charging voltage and current messages sent from the smart
`battery and can dynamically adjust its output characteristics. Using the charging
`algorithm in the battery, the level 2-charger may simply set a charge condition once
`or may adjust its output periodically to meet the needs of the changing battery.
`Thus, a level-2 charger is chemistry independent.
`
`A level-3 charger is an SMBus master device. This charger can poll the battery to
`determine the battery's desired charging voltage and current and can dynamically
`adjust its output to meet the battery's charging requirements. In addition to all
`capabilities of a level-2 charger, a level-3 charger can also implement an alternative
`specialized charging algorithm and can interrogate the battery for any relevant data,
`such as time remaining to full charge, battery temperature, or other data used to
`control proper charging and discharging.
`
`To order a copy of the Smart-Battery and SMBus specification, call (503) 797-4216
`or (800) 253-3696, or e-mail ial_product@ccm.hf.intel.com and specify product
`code SBS5220.
`
`The advantages of a high IQ
`
`The advantages of an intelligent battery or intelligent battery-management system are clear: longer
`run times, longer lifetimes, and more end-user confidence in the battery information. Batteries that
`can deliver accurate information about their state of charge let you use all of that available charge
`more fully. Shorter charge times, which must be commensurate with controlled charging, result in
`longer run times. And, proper handling of the battery results in the longest possible life for that
`battery.
`
`Depending on the specific implementation, other advantages include a management scheme that can
`recognize and handle batteries of different chemistries. The Duracell/Intel spec and many of the
`battery-management products can currently deal with numerous battery chemistries, including NiCd,
`NiMH, Li-ion, and lead acid. In addition, many ICs tailored specifically for Li-ion batteries will
`appear this year.
`
`One of the greatest advantages of smart batteries or systems is the power-management possibilities
`they offer to a system engineer. These batteries provide a wealth of information that you can use to
`develop a proprietary power-management scheme, regardless of whether you use a standard battery or
`communication protocol. Dave Heacock of Benchmarq Microelectronics suggests adaptive charge
`control as one such technique. Using information from an intelligent battery, you could design a
`system that caters its sensitivity to the reported battery state. If you know a battery is empty, you
`could design the system to apply the full charge current. Once the battery fills up, the system could
`increase the sensitivity to identify the end-of-charge point very closely.
`
`http://www.embedded.com/print/4350382
`
`5/6/2015
`Exhibit 1018, Page 005
`
`

`

`Page 6 of 13
`
`What's a smart battery?
`There is no standard definition of a "smart" battery. Duracell defines a smart battery
`as "a rechargeable battery equipped with a microchip that collects and
`communicates present, calculated, and predicted battery information to the host
`system-notebook computer, cellular phone, etc-under software control."
`Aside from this definition that implies a hardware configuration, there is a general
`consensus on at least some of the qualifying features of an intelligent battery and
`associated battery-management systems. These features can include the battery
`performing accurate self-monitoring; implementing its charge-regime control;
`communicating with its host; implementing fault identification/protection; and
`storing pertinent information, including its charge/discharge cycle history.
`
`This list of intelligent-battery features may seem to imply that the intelligence has to
`reside in the battery pack, but this is not always true. In some cases, separate circuits
`make more sense.
`
`PICTURE
`
`Duracell's first products to meet the Duracell/Intel Smart-Battery Specification, the Smart
`Rechargeable Batteries, indicate remaining capacity and run time within an estimated 1%. The
`batteries have an on-pack LED that indicates remaining battery life in increments of 25%.
`
`Smart-battery qualities
`
`In some cases, a truly self-contained smart battery may be the right choice for your product. However,
`you have other choices. Although the Duracell/Intel specification's goal is standardization, the spec
`has flexibility and contains many implementation layers from which you can pick and choose. For
`example, a high-end computer may include all smart-battery electronics in the battery pack, but the
`same computer manufacturer could also produce a cheaper line with a slightly modified battery pack.
`
`While standardization is under debate, you can choose how much intelligence to design in and where
`to locate it (see box, "Looking ahead," pg 59). A certain level of intelligence may suit one product but
`be overkill for another. The requirements of the notebook-computer user differs greatly from the
`occasional cellular-phone user, for example.
`
`Obviously, much of what you design depends on the product's battery chemistry or on the desire to
`handle multiple chem-istries. Remember: Every battery has a unique personality profile (see Ref 1).
`Battery characteristics change over time (self-discharge), with temperature, and with use and abuse.
`The battery type can experience varying degrees of these changes, and you have to account for these
`changes when choosing a battery-management scheme.
`
`The complexity of the control schemes may impact your battery choice. For any product, the
`advantages of NiMH or even Li-ion batteries may not outweigh the costs of controlling them.
`Rayovac's Renewal alkaline batteries-which are suited more for low-power, handheld devices than for
`notebook computers-have very low self-discharge rates, so predicting remaining charge doesn't
`require as sophisticated a monitoring scheme as NiCd or NiMH batteries. An interesting feature of the
`
`http://www.embedded.com/print/4350382
`
`5/6/2015
`Exhibit 1018, Page 006
`
`

`

`Page 7 of 13
`
`Renewal battery is a mechanical interlock that allows a system to charge only the Renewal battery
`while running on another battery of a different chemistry.
`
`Currently, you can implement either a full-blown smart battery or an intermediate level of battery
`management in three ways: You can use a fully integrated, retail smart battery, such as the DR15, 17,
`30, 35, and 36 from Duracell. You can work with a manufacturer, such as Energizer Power Systems
`or Sanyo Energy, on a unique design based on a fully integrated smart battery. Or, you can mix and
`match products from companies that design battery-management and charge-control ICs,
`microcontrollers, and software.
`
`Duracell's batteries epitomize the use of a fully integrated, retail smart battery. The company's smart
`batteries conform to one of five form factors with varying levels of capacity.
`
`Products from Energizer Power Systems and Sanyo Energy epitomize the second approach. The
`companies have more or less a custom working relationship with OEM customers and offer design
`flexibility for the electronic design and hardware form factor. For example, when working with
`Energizer Power Systems, you can implement any proprietary bus system and battery-data set, or you
`can actually emulate elements of the Duracell/Intel Smart-Battery and SMBus specification.
`
`Energizer Power Systems worked with National Semiconductor for the design of the actual silicon,
`which works with a variety of manufacturers' batteries and, thus, suits the final mix-and-match option.
`The chip set ($8 to $10 for the highest end) consists of the LMC6980 intelligent-battery development
`system and the LMC6984 intelligent-battery embedded controller (Fig 1 shows a typical application
`circuit).
`FIGURE 1
`
`The LMC6980 and LMC6984 chip set from National Semiconductor, along with some external
`components, such as the LM2936 low-dropout regulator and LM35 temperature sensor,
`implement an intelligent-battery charge-control system. The LMC6980 performs data-
`acquisition functions and contains internal EEPROM; the LMC6984 contains charge-control
`firmware.
`
`The LMC6980 contains the analog data-acquisition circuitry to monitor the battery's voltage,
`temperature, and dynamic current. The IC is unique because it contains 128 bytes of internal
`embedded EEPROM for storing numerous battery and charge-termination parameters. The LMC6984
`contains all of the charge-control functions implemented by one of two versions of firmware. One is
`standard µC code. The other, which the company calls NeuFuz, is code the company derived using
`neural fuzzy-logic algorithms. The fuzzy-logic charge-control algorithms implement a charge time
`much faster than the typical two to three hours. Tests performed on NiCd batteries show charge times
`of around 20 to 30 minutes.
`
`Other products that implement the mix-and-match approach are either complete battery-management
`ICs that you team with a selected battery, such as Benchmarq's bq2040 ($7 (1000)) and Microchip
`Technology's MTA-11200 ($3.75 (10,000)), or stand-alone gas-gauge and control ICs. Linear
`Technology's LT1325 contains a gas gauge and charge controller but requires the use of an external
`µC, typically the keyboard controller.
`
`http://www.embedded.com/print/4350382
`
`5/6/2015
`Exhibit 1018, Page 007
`
`

`

`Page 8 of 13
`
`Note: You'll find essentially three types of individual ICs or chip sets: stand-alone charge ICs, stand-
`alone gas-gauge ICs, and battery-management ICs. The term battery management usually implies that
`the IC performs both charge control and monitoring of the battery. There are many inexpensive ICs
`available for charge control, but they don't determine battery capacity.
`
`Some of the products are specialized ICs, and others are µCs specialized for battery-management
`functions. The MTA11200's design includes the company's 8-bit µC core and, based on a license
`agreement with Span Inc, uses purely digital methods to integrate battery charge and discharge
`current. Zilog Inc discusses a smart charger based solely on it Z8 µC in Ref 2.
`
`The debate over smart-battery standards
`Any move toward standardization has its detractors, particularly those who don't
`want to disclose or change the use of their leading-edge technology. Critics of a
`standard smart battery object because they want to use a unique power-management
`scheme. From a manufacturer's point of view, standard battery data-communication
`protocols and form factors diminish the value that they can add to their products
`even further.
`However, the Duracell/Intel Smart-Battery Specification appears open enough that
`these critics may not have to worry. The overall standards push has many layers
`from which OEM developers can pick and choose. In a broad sense, these layers are
`Intel's System-Management Bus, the battery data set and data-communication
`protocol, and the physical form factor. You can easily create products that use the
`SMBus, but don't necessarily conform to the data set in the Intel/Duracell
`specification or any standard-battery form factor. However, ultimately end users
`may have the say by demanding that battery packs be reusable in different systems.
`
`Mix-and-match trade-offs
`
`The bq2040 and bq2014 ($4.85 (10,000)) from Benchmarq Microelectronics highlight the trade-offs
`of various mix-and-match approaches. The 2040 is a gas-gauge IC that meets the Duracell/Intel
`SMBus interface and Smart-Battery Data specification. The 2014 is a proprietary stand-alone gas-
`gauge IC. Benchmarq teamed with SystemSoft to develop keyboard-controller software that translates
`the 2014's data to fit the Duracell/Intel spec. In this approach, the keyboard controller, rather than any
`IC in the battery pack, performs all the gas-gauge calculations. The bq2014 provides a more minimal
`data set than the bq2040 and has the minimum features necessary to do effective battery monitoring.
`Thus, the bq2014 is cheaper and more flexible, but doesn't provide as much information as the
`bq2040. Another difference that affects system implementation is that the bq2040 can't stop the
`charge but communicates its full status across the serial bus. The bq2014 can stop its own charging.
`
`Narrowing your choices
`
`When choosing a battery-management approach, you should consider numerous factors, including
`gas-gauge accuracy; charge control; cost; other required external hardware, such as temperature
`sensors and stable oscillators; level of standardization or, conversely, flexibility and programmability;
`
`http://www.embedded.com/print/4350382
`
`5/6/2015
`Exhibit 1018, Page 008
`
`

`

`Page 9 of 13
`
`development support; and the power consumption of the monitoring circuitry. Other than for
`development systems, none of the products surveyed with set pricing were over $10 in 10,000-piece
`quantities.
`
`The monitoring circuit's power consumption can be a big consideration, and you should determine
`how much operating and shutdown current any battery-management scheme requires. Most of the
`available ICs have shutdown and shelf-shutdown modes. In a part due this year, Microchip
`Technology will add a third "hibernate" power mode that draws 5 µA or less.
`PICTURE
`
`The heart of the Benchmarq Microelectronics' bq2040, a gas-gauge and charge-control IC with
`SMBus interface, is the accurate precision ADC and reference block that performs the gas
`gauging. This ADC is actually a V/F converter that uses conversion residuals for a net
`quantization error of zero.
`
`Gas-gauge accuracy is a must
`
`However, the most critical of the considerations are the accuracy of the monitoring circuit and
`implementation of the charge-control scheme.
`
`For effective battery management, the self-monitoring of the battery-the gas-gauge function-must be
`highly accurate. Without accuracy, no level of control can improve the battery's performance. To
`achieve a high level of accuracy, the gas-gauge electronics may have to compensate for changing
`battery parameters and perform calibration.
`
`A gas gauge measures some battery parameter that it uses to determine and report battery capacity
`(Ref 3). Some older, very inexpensive gas gauges simply measured voltage. This battery voltage is a
`highly inaccurate indication of a battery's capacity because it changes with temperature and battery
`load. Most of the more advanced gas-gauging products, including those discussed here, measure the
`current into and out of a battery to determine its capacity. Some manufacturers call this function
`coulomb counting.
`
`Although measuring current is much more accurate, each manufacturer's implementation and
`accuracy claims differ. Because of the integration of the battery packs with the control electronics,
`Duracell claims its smart batteries have extremely high accuracy of around 1%, stemming from their
`accurate cell models and calculation algorithms. Benchmarq points to the precision ADC and
`reference in the bq2040 as the main accuracy-determining components. A V/F converter that uses
`residuals from one conversion for the next conversion actually performs this ADC function. The net
`result is zero quantization error. Microchip's MTA11200 gets within 3% accuracy or better by using
`good internal components and a calibration with external components. According to National
`Semiconductor, having the data-acquisition portion of the battery-management system residing in the
`battery pack results in much higher accuracy than solutions that put this function in a separate
`charger.
`
`Note compensation
`
`http://www.embedded.com/print/4350382
`
`5/6/2015
`Exhibit 1018, Page 009
`
`

`

`Page 10 of 13
`
`Part of a gauge's accuracy stems from applying compensation for varying conditions and calibration.
`For example, Microchip's MTA11200 adjusts the charge-efficiency calculation based on the present
`state of charge and the temperature. To improve accuracy, the IC does not apply the compensation
`factors to the state-of-charge calculation when the battery is discharging.
`
`Also, a battery's capacity can vary over its lifetime, and, from time to time, many of these ICs need to
`self-calibrate and relearn 100% capacity. Benchmarq's bq2040 has an extra register that looks at
`discharge characteristics (Fig 2). If there have been no partial charges of the battery, the IC
`automatically updates capacity on a full-discharge cycle. When the battery reaches full charge, the IC
`resets capacity to full.
`FIGURE 2
`
`This operational overview shows how the bq2040 gas-gauge IC accumulates a measure of
`charge and discharge current, and estimates self-discharge while applying various types of
`compensation. The IC updates the main counter and registers and outputs the information to an
`LED or through a serial port.
`
`Capacity measurements should err on the conservative side and, after some number of partial charges,
`the system should inform the user that a full discharge is necessary.
`
`Choose the right charge control
`
`Charge-control schemes are also critical. All of the commonly accepted methods measure voltage,
`temperature, or their derivatives. For example, combinations of the dT/dt (change of temperature with
`time) and peak-voltage detect or dV/dt schemes (change of voltage with time) are recommended often
`for many batteries. For a time, negative delta-V, which detects the beginning of a negative voltage
`slope, was popular. According to some in the industry, the use of this technique appears to be waning
`in order to prevent overcharge of any battery type, including NiCds.
`
`In addition to effectiveness of the charge control, you may want to choose a management scheme that
`allows you to change the charge-control regime easily. One of the advantages of National
`Semiconductor's approach is its flexibility: You can implement many charge techniques. To change
`the charge-termination scheme, you simply change the EEPROM look-up tables in the 6980.
`Microchip's MTA11200 allows you to choose charge-control regimes for three battery chemistries
`and numerical value to stop charging. Changing a small portion of the controlling µC's code
`changes the LTC1325 charge-control regime.
`
`One final, important point about the charge-control scheme: It must be the one recommended by the
`battery manufacturer. Opinions and battery designs differ in the industry, and one NiMH
`manufacturer may recommend something slightly different than another. Don't second-guess battery
`manufacturers.
`
`Another feature of a smart-battery or system is its ability to store and maintain information, such as
`the number of charge/discharge cycles and temperature exposure extremes. Microchip coins the
`MTA11200's data-logging function as the "flight recorder" of the battery. This feature, based on
`
`http://www.embedded.com/print/4350382
`
`5/6/2015
`Exhibit 1018, Page 010
`
`

`

`Page 11 of 13
`
`external EEPROM, lets you log a number of charge cycles and check if the battery has gone above or
`below certain limits.
`
`The EEPROM data tables in National's LMC6980 holds values for load, data, and self-discharge
`correction. The EEPROM also stores three sets of phase termination and charge rates, min/max
`voltage and temperature limits, min/ max exposure temperatures, and the number of charge/discharge
`cycles.
`
`Development systems
`
`Development support is available for many of these battery-management schemes, including
`National's chip set, and Microchip Technology's MTA11200 ($499). Most include Windows-based
`software and some sort of demo board that includes the control and gas-gauge functions. These
`systems let you change various control parameters and test how the battery pack performs using those
`parameters. Benchmarq offers two versions of a development kit for its bq2040: a module ($25 each)
`that can fit on a pc board, or a larger pc board (the $149 EV2040) that you can hook to a battery pack.
`FIGURE 3
`
`Microchip Technology's MTA11200 battery-management IC implements a timed-voltage-ramp
`ADC that uses an external quad comparator in front of a RISC µC core. External EEPROM
`stores control parameters that customize the IC for a particular battery type and application.
`
`Smart batteries have limits
`
`Keep in mind what "smart" batteries can and can't do. They can report accurate state-of-charge
`information. They can implement a charge-control regime.
`
`However, a smart battery or battery-management system can't make up for improper desi