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1, about the trickle charge, rapid charging and stablebattery charging algorithm
According to the energy requirements of thefinalapplication, abatterymay contain up to 4lithiumion orlithium polymerbatterycore,its configuration will have a variety ofchange,at the sametime with amainstreampoweradapter: directadapter,USBinterface orcar charger. Remove thecore quantity,core configuration orpoweradapter type difference, thebatteryhas the same charge characteristics. So they charge algorithm.Lithiumion and li-ion polymerbattery best charging algorithm can divided into three phases: trickle charge, rapid charging and stable charge.
Advancedbattery charger withadditional security function normally. For example, if thecore temperature exceeds the given window, usually 0 ℃-45 ℃, charge will be suspended.
Remove some verylow-end equipment, nowon themarket/li-ion polymerlithiumionbattery solutions are integrated with theouter components or, inaccordance with the characteristics of the charging to charge, this is not just toget better effect charge, but also for safety.
LTC4097 can be used to exchangeadapter orUSBpower supply for single quarter/polymerlithiumionbattery. Figure 1 fordouble input 1.2 Alithiumbattery charger LTC4097schemes.It USES constant current/constant voltage algorithm charging, from exchangeadapterpower charge, programmable filling up to 1.2 electric current A, and withUSBpower can beas highas 1 A,at the sametime,automatic detection in each input voltage whether there. This device also provideUSB the current limit.Applications includePDA,MP3players,digital camera,lightportable medical andtest equipment andbigcolor cellular phone. The performance characteristics: no external micro controller charging termination; The inputpowerautomatic detection and choice; Through the resistance fromthe exchange of chargingadapter input can beas highas 1.2 A programming charge current; The resistance of programmableUSB charging current is up to 1 A;100% or20%USB charging currentset; The inputpower output and existing bias NTC (VNTC)pinas a120mA drive ability; NTC thermistors input (NTC)pin for temperature qualified charged; Pre-settingsbattery voltage with floating plus or minus 0.6%accuracy; Thermal regulationmaximize chargerate and free hotair LTC4097 can be used to exchangeadapter orUSBpower supply for single quarter/polymerlithiumionbattery. The use of constant current/constant voltage algorithm charging, from exchangeadapterpower charge, programmable filling up to 1.2 electric current A, and withUSBpower can beas highas 1 A,at the sametime,automatic detection in each input voltage whether there. This device also provideUSB the current limit.Applications includePDA,MP3players,digital camera,lightportable medical andtest equipment andbigcolor cellular phone.
2,lithiumion/polymerbatteryscheme
Lithiumion/polymerbattery chargescheme for differentnumber ofcore,core configuration, andpower types are different.At presentmainly have threemain chargingscheme:linear, Buck (step-down)switch and SEPIC (booster and step-down)switch.
When the input voltage inbig with the charger with sufficient clearance ofcore afteropening voltage,it islinearscheme, especially 1.0 C fast charging current than 1 Abig too much. For example,MP3players usuallyonlyonecore, capacity from 700 to 1500mAh differ, full charge voltage isopen 4.2 V.MP3 playerpower is usually theAC/DCadapter orUSBinterface, the output is the rule of 5 V;At this time, thelinearscheme isthe most simple, most charger of the efficiency of thescheme. Figure 2 shows forlithiumion/polymerbattery solutionlinearscheme,basicstructure andlinear voltageneat device.
MAX8677A isdouble inputUSB/ACadapterlinear charger, built-inSmartPower Selector, used for rechargeable single quarterby Li + batteriesportable devices. The charger integration of thebattery andthe externalpower source and loadswitch chargingall thepowerswitch, so that no externalMOSFET.MAX8677A ideal used inportable devices, suchassmartphones,PDA,portable mediaplayers,GPS navigation equipment,digital camera, anddigital cameras.
MAX8677A can work in independentUSB and thepower inputACadapter ortwo input eitherone of the input. Whenconnecting externalpower supply, intelligentpower source selectorallows the system notconnectbattery or can and depth dischargebatteryconnection. Intelligentpower source selector willautomaticallyswitch to thebattery system load, use the system did not use the inputpower supply parts forbattery,make full use of limitedUSBand adapterpower supply input.All theneeded electric current detection circuit, including the integration of thepowerswitch,all integration in the piece.DC input current highest limit can be adjusted to 2 A andDC andUSB inputall can support100mA, 500mA, andUSB hung mode. Charge current can be adjusted toas highas 1.5 A, thus support wide range ofbattery capacitive. Other features includeMAX8677A thermal regulation,over-voltage protection, charging status and fault output,power supply good surveillance,battery thermistors surveillance, and chargingtimer.MAX8677A using save a space, hot enhanced, 4mm x 4mm,24 of thepins TQFN encapsulation, regulations, work in exceptional temperature range (40 ~ + 85 ℃).
2.2 Buck (step-down)switchscheme
When A 1.0 C of the charging currentmore than 1 A, or the input voltage of thecore than withhigh voltageopenmany, Buck or step-down plan is A better choice. For example, basedon the hard drive in thePMP, often use singlecorelithiumionbattery, the full ofopen is 4.2 V voltage, capacity from1200 to2400mAh range. And nowPMP is usually use thecar kit to charge,its output voltage in a 9 V to 16 between V. In the input voltage andbattery voltage is the voltage difference between high (minimum 4.8 V) willmakelinearschemelowers efficiency. This kind oflow efficiency, plusmore than 1.2 A 1 C fast charging electric current, have seriousheat dissipation problems. To avoid this kind of situation, will the Buckscheme. Figure 3 forlithiumion/polymerbattery chargerscheme Buck diagram,basicstructure with Buck (step-down)switching voltage regulators completely the same.
2.3 SEPIC (booster and step-down)switchscheme
In some use of three or fourlithiumion/polymercore series equipments, charger of the input voltage is notalways greater than thebattery voltage. For example, laptop computers use 3corelithiumionbattery, full charge voltage isopen12.6 V (4.2 Vx3), capacity is 1800mAh to 3600mAh from.Power supply input or output voltage is 1 6 VAC/DCadapter, or iscar kit, the output voltage in a 9 V to 16 between V. Apparently, thelinear and Buck solutions are not for thisgroup of batteries. This is about to use SEPICscheme,it can in the output voltage is higher than when thebattery voltage, can be in the output voltage less than when thebattery.
3, andpower detection algorithm is proposed
Manyportable products use voltage measurements to estimate the remainingbatterypower, but thebattery voltage and surpluspower relationship but will with the dischargerate, temperature andbattery aging degree ofchange,make this kind of method cantop 50%margin of error. Themarket for longer to use product demand unceasingly strengthens, so the system design personnelneedmoreaccurate solution. Use capacity check plan come to measurebattery or consumption of electricity, will be in a wide range ofapplicationpower to providemoreaccurate estimate of thebatterypower.
3.1power detection algorithm isone ofthe examples ofapplication, function complete list,double thebatteryportablebatteryapplication design
Thebattery circuit description. Figure 4 (a) can be used for identification ofIC functions with typicalapplication circuit batteries.According to the use ofICtesting program is different, thebatteryneeds to haveat least three to four outside the terminal.
VCC and BATpins will even to thebattery voltage, so that for, Cpower and thebattery voltage measurement. Thebattery isconnected a grounding resistance smaller detection resistors, let capacity check meter high impedance SRP and SRN input can monitor sensor resistanceon bothends of the voltage. Throughtesting the currentflows through a resistor can be used to judge thebattery or release the amount of electricity. Designers choose detection resistance value must be considered when resistanceon bothends of the voltage can'tmore than100mV,low resistancemay bemore hours in current errors. Circuit board layout must ensure that SRP and SRN totesting fromas closeas possible to theconnection of the resistor sensor resistance end; In other words, they should be the Kelvinattachment.
HDQpinneed external and resistors, this resistance should be located the host or themainapplication, such capacity check plan to thebattery andportable devices when sleep functionenableconnection broken. Advice and resistance choose10 k Ω.
Once thebattery through the appraisal, bq26150 will issuecommands to ensure that the host and quantitytest plan ofmaterial lines between normal communication. When thebatteryconnection interruption or toconnect,the whole the identification process will be repeatedagain.
Host to be able to read capacity check plan of variable voltage measurementbattery, tomake sure the end of discharging threshold and charging terminate threshold.As for the remainingstatepower (RemainingStateofCapacity), do notneed to read can use directly.
The above bq2650x and bq27x00etc capacity check plan provides thebatterymanufacturer a simple to use options, thisscheme L [just measuringbattery voltage to be precise, so these capacity check plan can be applied to variousbatteryframework, and can support thebattery identification anddouble thebatteryapplication '
3.2power detection algorithm is an example ofapplicationsanother, can apply toall kinds of general voltmeter newIC.
Today'smanymanufacturers can provide a variety of voltmeterIC,, theuser can choose the suitable function device, to optimize the product price. Use voltmeter measurement of storagebattery parameters, the separate architectureallowsusers in the host custompower measurement algorithm within. Eliminating embedded processorbattery cost.On this to Dallase semicconductor company called cases of DS2762chip for typical analysis. A new separate voltmeterIC,itsstructure see chart 5 (a) below.
DS2762 is a single quarter oflithiumbattery voltmeter and protection circuit, integrated into a tiny 2.46mm x 2.74mm inversion of packaging. Due to internal integration forpower detection of high precise resistance, this device is very save a space.It is the small size and incomparable highlevel of integration, for mobile phonebattery and other similar handheld products, suchasPDA,etc, areall very ideal. Integrated protection circuit continuously monitoring thebattery voltage,over voltage andflow fault (charging or discharge period). Different from the independent protectionIC, DS2762allowmain processor surveillance/control protection FET conductionstate, such, can DS2762 through the protection of thepower system and the control circuit implementation. DS2762 can also charge abattery consumptionhas depth, when thebattery voltage within three V, provide a limit of the charging current recovery path.
DS2762accurate monitoringbattery current, voltage and temperature, the dynamic range andresolution ofcommon satisfy any mobile communication producttesting standards. The measurement of current for internally generated when the integral,realize thepower measurement. Through the real-time, continuousautomatic disorders correct, the precision ofpower measurement can be increased. The built-in measuring resistance due to eliminatemanufacturing process and temperature and cause resistancechange, further improve the precision of the voltmeter. Important data stored in 32bytes, canadd the lock EEPROM; 16bytes ofSRAM are used to keep dynamic data. And DS2762all communicationall through the 1-Wire,more communicationinterface node, minimize thebattery and theconnection to the host.Itsmain features for; Single quarter oflithiumbattery protector; High precision current (power measurement), voltage and temperature measurement; Optional integrated 25 m Ω measuring resistance, each DS2762 after fine-tuning alone; 0 Vbattery restore charge; 32bytes can lock EEPROM, 16bytesSRAM, 64 aROM;
1-Wire, node,digital communicationinterface; Supportmorebatterypower management, and through the protection system control FETpower; Dormancy modepower supply currentonly 2 µ A (most); Work modepower supply current for 90 µ A (most); 2.46mm x 2.74mm inversion of packaging or 16 feet SSOP packageled, and both are can choose with or without detection resistance; Afterhas with e
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