MEMORY存储芯片LTC4054ES5-4.2中文规格书 - 图文

DESCRIPTIOsssssssssssssssUAPPLICATIO SsssProgrammable Charge Current Up to 800mANo MOSFET, Sense Resistor or BlockingDiode RequiredComplete Linear Charger in ThinSOTTM Package forSingle Cell Lithium-Ion BatteriesConstant-Current/Constant-Voltage Operation withThermal Regulation* to Maximize Charge RateWithout Risk of OverheatingCharges Single Cell Li-Ion Batteries Directlyfrom USB PortPreset 4.2V Charge Voltage with ±1% AccuracyCharge Current Monitor Output for GasGauging*Automatic RechargeCharge Status Output PinC/10 Charge Termination25μA Supply Current in Shutdown2.9V Trickle Charge Threshold (LTC4054)Available Without Trickle Charge (LTC4054X)Soft-Start Limits Inrush CurrentAvailable in 5-Lead SOT-23 PackageThe LTC?4054 is a complete constant-current/constant-voltage linear charger for single cell lithium-ion batteries.Its ThinSOT package and low external component countmake the LTC4054 ideally suited for portable applications.Furthermore, the LTC4054 is specifically designed to workwithin USB power specifications.No external sense resistor is needed, and no blockingdiode is required due to the internal MOSFET architecture.Thermal feedback regulates the charge current to limit thedie temperature during high power operation or highambient temperature. The charge voltage is fixed at 4.2V,and the charge current can be programmed externally witha single resistor. The LTC4054 automatically terminatesthe charge cycle when the charge current drops to 1/10ththe programmed value after the final float voltage isreached.When the input supply (wall adapter or USB supply) isremoved, the LTC4054 automatically enters a low currentstate, dropping the battery drain current to less than 2μA.The LTC4054 can be put into shutdown mode, reducingthe supply current to 25μA.Other features include charge current monitor, undervoltagelockout, automatic recharge and a status pin to indicatecharge termination and the presence of an input voltage., LTC and LT are registered trademarks of Linear Technology Corporation.ThinSOT is a trademark of Linear Technology Corporation.*U.S.Patent No. 6,522,118Cellular Telephones, PDAs, MP3 PlayersCharging Docks and CradlesBluetooth ApplicationsTYPICAL APPLICATIOVIN4.5V TO 6.5VComplete Charge Cycle (750mAh Battery)700600CONSTANTCURRENTCONSTANTPOWERCONSTANTVOLTAGE4.754.50600mA Single Cell Li-Ion ChargerCHARGE CURRENT (mA)50040030020010001μFBATLTC4054-4.2PROGGND24VCC3600mA51.65k4.2VLi-IonBATTERY405442 TA01aVCC = 5VθJA = 130°C/WRPROG = 1.65kTA = 25°C03.000.250.50.751.01.251.51.752.0TIME (HOURS)405442 TAO1b405442xfUBATTERY VOLTAGE (V)4.254.003.753.50CHARGETERMINATED3.25FEATURESULTC4054-4.2/LTC4054X-4.2BLOCK DIAGRA 4VCC120°CTATDIE1×1000×MACA–+–SHDNC1R31VR4+1CHRGSTANDBYTRICKLE CHARGEDISABLED ONLTC4054XC33μAC20.1VR5–+–TOBAT2.9V5PROGVCC+–+W5μAR1BAT3+VAR2–REF1.21VGNDRPROG2405442 BD405442xfLTC4054-4.2/LTC4054X-4.2

UOPERATIOThe LTC4054 is a single cell lithium-ion battery chargerusing a constant-current/constant-voltage algorithm. Itcan deliver up to 800mA of charge current (using a goodthermal PCB layout) with a final float voltage accuracy of±1%. The LTC4054 includes an internal P-channel powerMOSFET and thermal regulation circuitry. No blockingdiode or external current sense resistor is required; thus,the basic charger circuit requires only two external com-ponents. Furthermore, the LTC4054 is capable of operat-ing from a USB power source.Normal Charge CycleA charge cycle begins when the voltage at the VCC pin risesabove the UVLO threshold level and a 1% program resistoris connected from the PROG pin to ground or when abattery is connected to the charger output. If the BAT pinis less than 2.9V, the charger enters trickle charge mode.In this mode, the LTC4054 supplies approximately 1/10the programmed charge current to bring the battery volt-age up to a safe level for full current charging. (Note: TheLTC4054X does not include this trickle charge feature).When the BAT pin voltage rises above 2.9V, the chargerenters constant-current mode, where the programmedcharge current is supplied to the battery. When the BATpin approaches the final float voltage (4.2V), the LTC4054enters constant-voltage mode and the charge currentbegins to decrease. When the charge current drops to1/10 of the programmed value, the charge cycle ends.Programming Charge CurrentThe charge current is programmed using a single resistorfrom the PROG pin to ground. The battery charge currentis 1000 times the current out of the PROG pin. Theprogram resistor and the charge current are calculatedusing the following equations:IBAT=VPROG?1000RPROGCharge TerminationA charge cycle is terminated when the charge current fallsto 1/10th the programmed value after the final float voltageis reached. This condition is detected by using an internal,filtered comparator to monitor the PROG pin. When thePROG pin voltage falls below 100mV1 for longer thantTERM (typically 1ms), charging is terminated. The chargecurrent is latched off and the LTC4054 enters standbymode, where the input supply current drops to 200μA.(Note: C/10 termination is disabled in trickle charging andthermal limiting modes).When charging, transient loads on the BAT pin can causethe PROG pin to fall below 100mV for short periods of timebefore the DC charge current has dropped to 1/10th theprogrammed value. The 1ms filter time (tTERM) on thetermination comparator ensures that transient loads ofthis nature do not result in premature charge cycle termi-nation. Once the average charge current drops below1/10th the programmed value, the LTC4054 terminatesthe charge cycle and ceases to provide any current throughthe BAT pin. In this state, all loads on the BAT pin must besupplied by the battery.The LTC4054 constantly monitors the BAT pin voltage instandby mode. If this voltage drops below the 4.05Vrecharge threshold (VRECHRG), another charge cycle be-gins and current is once again supplied to the battery. Tomanually restart a charge cycle when in standby mode, theinput voltage must be removed and reapplied, or thecharger must be shut down and restarted using the PROGpin. Figure 1 shows the state diagram of a typical chargecycle.Charge Status Indicator (CHRG)The charge status output has three different states: strongpull-down (~10mA), weak pull-down (~20μA) and highimpedance. The strong pull-down state indicates that theLTC4054 is in a charge cycle. Once the charge cycle hasterminated, the pin state is determined by undervoltageNote 1: Any external sources that hold the PROG pin above 100mV will prevent the LTC4054from terminating a charge cycle.405442xf

1000V1000VRPROG=,ICHG=ICHGRPROGThe charge current out of the BAT pin can be determinedat any time by monitoring the PROG pin voltage using thefollowing equation:LTC4054-4.2/LTC4054X-4.2UOPERATIOlockout conditions. A weak pull-down indicates that VCCmeets the UVLO conditions and the LTC4054 is ready tocharge. High impedance indicates that the LTC4054 is inundervoltage lockout mode: either VCC is less than 100mVabove the BAT pin voltage or insufficient voltage is appliedto the VCC pin. A microprocessor can be used to distin-guish between these three states—this method is dis-cussed in the Applications Information section.Thermal LimitingAn internal thermal feedback loop reduces the programmedcharge current if the die temperature attempts to riseabove a preset value of approximately 120°C. This featureprotects the LTC4054 from excessive temperature andallows the user to push the limits of the power handlingcapability of a given circuit board without risk of damagingthe LTC4054. The charge current can be set according totypical (not worst-case) ambient temperature with theassurance that the charger will automatically reduce thecurrent in worst-case conditions. ThinSOT power consid-erations are discussed further in the Applications Informa-tion section.Undervoltage Lockout (UVLO)An internal undervoltage lockout circuit monitors the inputvoltage and keeps the charger in shutdown mode until VCCrises above the undervoltage lockout threshold. The UVLOcircuit has a built-in hysteresis of 200mV. Furthermore, toprotect against reverse current in the power MOSFET, theUVLO circuit keeps the charger in shutdown mode if VCCfalls to within 30mV of the battery voltage. If the UVLOcomparator is tripped, the charger will not come out ofshutdown mode until VCC rises 100mV above the batteryvoltage.Manual ShutdownAt any point in the charge cycle, the LTC4054 can be putinto shutdown mode by removing RPROG thus floating thePROG pin. This reduces the battery drain current to lessPROGRECONNECTEDORUVLO CONDITIONSTOPSthan 2μA and the supply current to less than 50μA. A newcharge cycle can be initiated by reconnecting the programresistor.In manual shutdown, the CHRG pin is in a weak pull-downstate as long as VCC is high enough to exceed the UVLOconditions. The CHRG pin is in a high impedance state ifthe LTC4054 is in undervoltage lockout mode: either VCCis within 100mV of the BAT pin voltage or insufficient voltageis applied to the VCC pin.Automatic RechargeOnce the charge cycle is terminated, the LTC4054 continu-ously monitors the voltage on the BAT pin using a com-parator with a 2ms filter time (tRECHARGE). A charge cyclerestarts when the battery voltage falls below 4.05V (whichcorresponds to approximately 80% to 90% battery capac-ity). This ensures that the battery is kept at or near a fullycharged condition and eliminates the need for periodiccharge cycle initiations. CHRG output enters a strong pull-down state during recharge cycles.POWER ONBAT < 2.9VTRICKLE CHARGEMODE1/10TH FULL CURRENTCHRG: STRONGPULL-DOWNBAT > 2.9VSHUTDOWN MODEICC DROPS TO <25μACHRG: Hi-Z IN UVLOWEAK PULL-DOWNOTHERWISECHARGE MODEFULL CURRENTCHRG: STRONGPULL-DOWNPROG < 100mVSTANDBY MODENO CHARGE CURRENTPROG FLOATEDORUVLO CONDITIONCHRG: WEAKPULL-DOWN2.9V < BAT < 4.05V405442 F01BAT > 2.9VFigure 1. State Diagram of a Typical Charge Cycle405442xfLTC4054-4.2/LTC4054X-4.2

APPLICATIO S I FOR ATIOStability ConsiderationsThe constant-voltage mode feedback loop is stable with-out an output capacitor provided a battery is connected tothe charger output. With no battery present, an outputcapacitor is recommended to reduce ripple voltage. Whenusing high value, low ESR ceramic capacitors, it is recom-mended to add a 1? resistor in series with the capacitor.No series resistor is needed if tantalum capacitors areused.In constant-current mode, the PROG pin is in the feedbackloop, not the battery. The constant-current mode stabilityis affected by the impedance at the PROG pin. With noadditional capacitance on the PROG pin, the charger isstable with program resistor values as high as 20k. How-ever, additional capacitance on this node reduces themaximum allowed program resistor. The pole frequencyat the PROG pin should be kept above 100kHz. Therefore,if the PROG pin is loaded with a capacitance, CPROG, thefollowing equation can be used to calculate the maximumresistance value for RPROG:U10kPROGLTC4054GNDRPROGCFILTERCHARGECURRENTMONITORCIRCUITRY405442 F02WUUFigure 2. Isolating Capacitive Load on PROG Pin and FilteringPower DissipationThe conditions that cause the LTC4054 to reduce chargecurrent through thermal feedback can be approximated byconsidering the power dissipated in the IC. Nearly all ofthis power dissipation is generated by the internalMOSFET—this is calculated to be approximately:PD = (VCC – VBAT) ? IBATwhere PD is the power dissipated, VCC is the input supplyvoltage, VBAT is the battery voltage and IBAT is the chargecurrent. The approximate ambient temperature at whichthe thermal feedback begins to protect the IC is:405442xf