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1、Standalone Linear Li-Ion Battery Charger in ThinSOT General Description Features Applications Cellular Telephones,PDAs,MP3 Players Charging Docks and Cradles Bluetooth Applications ME4054 is a constant-current/constant-voltage linear charger for single cell lithium-ion batteries.Its Thin SOT package
2、 and low external component count make the ME4054 ideally suited for portable applications.Furthermore,the ME4054 is specifically designed to work within USB power specifications.No external sense resistor is needed,and no blocking diode is required due to the internal MOSFET architecture.Thermal fe
3、edback regulates the charge current to limit the die temperature during high power operation or high ambient temperature.The charge voltage is fixed at,and the charge current can be programmed externally with a single resistor.The ME4054 automatically terminates he charge cycle when the charge curre
4、nt drops to 1/10th the programmed value after the final float voltage is reached.Programmable Charge Current Up to 800mA No MOSFET,Sense Resistor or Blocking Diode Required Complete Linear Charger in ThinSOT Package for Single Cell Lithium-Ion Batteries Constant-Current/Constant-Voltage Operation wi
5、th Thermal Regulation to Maximize Charge Rate Without Risk of Overheating Charges Single Cell Li-Ion Batteries Directly from USB Port Preset Charge Voltage with 1%Accuracy Automatic Recharge 600mA Single Cell Li-Ion Charger VIN Complete Charge Cycle(750mAh Battery)Pin Configuration Pin Assignment Pi
6、n Symbol Description SOT23-5 1 CHRG Open-Drain Charge Status Output 2 GND Ground JA 3 BAT Charge Current Output 4 VCC Positive Input Supply Voltage 5 PROG Charge Current Program 1F 600mA Li-Ion GND PROG BAT VCC ME4054 2 3 4 5 CONSTANT CURRENT CONSTANTPOWCONSTANT VCC=5V JA=130/W R=CHARGE 1 BATTERY VO
7、LTAGE(V)700 600 500 400 300 200 100 CHARGE CURRENT(mA)0 TIME(HOURS)2 3 4 5 PROG VCC CHRG GND BAT Block Diagram Absolute Maximum Ratings 120 TDIE TA VCC 1x MA VA 1000 x BAT R1 R2 REF R3 1V R4 CA C1 C2 C3 SHDN CHRG PROG GND 1 2 5 3 4 TO BAT VCC 3A 5A Parameter Ratings Input Supply Voltage(VCC)10V PROG
8、 Vcc BAT 7V CHRG 10V BAT Short-Circuit Duration Continuous BAT Pin Current 800mA PROG Pin Current 800A Maximum Junction Temperature 125 Operating Ambient Temperature Range-4085 Storage Temperature Range-65125 Lead Temperature(Soldering,10 sec)260 Caution:The absolute maximum ratings are rated values
9、 exceeding which the product could suffer physical damage.These values must therefore not be exceeded under any conditions.Electrical Characteristics SYMBOL PARAMETER CONDITIONS MIN TYP MAX Unit VCC Input Supply Voltage V ICC Input Supply Current Charge Mode，RPROG=10K-300 2000 A Standby Mode(Charge
10、Terminated)-200 500 A Shutdown Mode（RPROG Not Connected，VCCVBAT）-25 50 A VFLOAT Regulated Output(Float)Voltage 0TA85,IBAT=40mA V IBAT BAT Pin Current RPROG=10K,Current Mode 93 100 107 mA RPROG=2K,Current Mode 465 500 535 mA Standby Mode，VBAT 0 -6 A Shutdown Mode（RPROG Not Connected）-1 2 A Sleep Mode
11、,VCC0V 1 2 A ITRILK Trickle Charge Current VBATVTRILK,RPROG2K 20 45 70 mA VTRILK Trickle Charge Threshold Voltage RPROG10K,VBAT Rising V VTRHYS Trickle Charge Hysteresis Voltage RPROG10K 60 80 110 mV VUV VCC Undervoltage Lockout Threshold From VCC Low to High V VUVHYS VCC Undervoltage Lockout Hyster
12、esis 150 200 300 mV VMSD Manual Shutdown Threshold Voltage PROG Pin Rising V PROG Pin Falling V VADS VCC-VBAT Lockout Threshold Voltage VCC from Low to High 70 100 140 mV VCC from High to Low 5 30 50 mV ITERM C/10 Termination Current Threshold RPROG10K mA RPROG2K mA VPROG PROG Pin Voltage RPROG10K,C
13、urrent Mode V ICHRG CHRG Pin Weak Pull-Down Current VCHRG5V 8 20 35 A VCHRG CHRG Pin Output Low ICHRG5mA V VRECHRG Recharge Battery Threshold Voltage VFLOATVRECHRG 100 150 200 mV TLIM Junction Temperature in Constant Temperature Mode -120-RON Power FET“ON”Resistance(Between VCC and BAT)-600-m TSS So
14、ft-Start Time IBAT0 to IBAT1000V/RPROG 100 S TRE Recharge Comparator Filter Time VBAT High to Low 2 mS TTERM Termination Comparator Filter Time IBAT Falling Below ICHG/10 400 1000 2500 S IPROG PROG Pin Pull-Up Current -3-A Note:The denotes specifications which apply over the full operating temperatu
15、re rang,otherwise specifications are at TA=25，VCC=5V，unless otherwise specified.Typical performance characteristics Description of the Principle The ME4054 is a single cell lithium-ion battery charger using a constant-current/constant-voltage algorithm.It can deliver up to 800mA of charge current(us
16、ing a good thermal PCB layout)with a final float voltage accuracy of1%.The ME4054 includes an internal P-channel power MOSFET and thermal regulation circuitry.No blocking diode or external current sense resistor is required;thus,the basic charger circuit requires only two external components.Further
17、more,the ME4054 is capable of operating from a USB power source.Charge Cycle A charge cycle begins when the voltage at the VCC pin rises above the UVLO threshold level and a 1%program resistor is connected from the PROG pin to ground or when a battery is connected to the charger output.If the BAT pi
18、n is less than,the charger enters trickle charge mode.In this mode,the ME4054 supplies approximately 1/10 the programmed charge current to bring the battery voltage up to a safe level for full current charging.When the BAT pin voltage rises above,the charger enters constant-current mode,where the pr
19、ogrammed charge current is supplied to the battery.When the BAT pin approaches the final float voltage,the ME4054 enters constant-voltage mode and the charge current begins to decrease.When the charge current drops to 1/10 of the programmed value,the charge cycle ends.Charge Current The charge curre
20、nt is programmed using a single resistor from the PROG pin to ground.The battery charge current is 1000 times the current out of the PROG pin.The program resistor and the charge current are calculated using the following equations:RPROG=1000V/ICHG,ICHG=1000V/RPROG The charge current out of the BAT p
21、in can be determined at any time by monitoring the PROG pin voltage using the following equation:IBAT=1000*VPROG/RPROG Termination A charge cycle is terminated when the charge current falls to 1/10th the programmed value after the final float voltage is reached.This condition is detected by using an
22、 internal,filtered comparator to monitor the PROG pin.When the PROG pin voltage falls below 100mV for longer than tTERM(typically 1ms),charging is terminated.The charge current is latched off and the ME4054 enters standby mode,where the input supply current drops to 200A.(Note:C/10 termination is di
23、sabled in trickle charging and thermal limiting modes).When charging,transient loads on the BAT pin can cause the PROG pin to fall below 100mV for short periods of time before the DC charge current has dropped to 1/10th the programmed value.The 1ms filter time(tTERM)on the termination comparator ens
24、ures that transient loads of this nature do not result in premature charge cycle termination.Once the average charge current drops below 1/10th the programmed value,the ME4054 terminates the charge cycle and ceases to provide any current through the BAT pin.In this state,all loads on the BAT pin mus
25、t be supplied by the battery.The ME4054 constantly monitors the BAT pin voltage in standby mode.If this voltage drops below the recharge threshold(VRECHRG),another charge cycle begins and current is once again supplied to the battery.To manually restart a charge cycle when in standby mode,the input
26、voltage must be removed and reapplied,or the charger must be shut down and restarted using the PROG pin.Figure 1 shows the state diagram of a typical charge cycle.Status Indicator(CHRG)The charge status output has three different states:strong pull-down(10mA),weak pull-down(20 A)and high impedance.T
27、he strong pull-down state indicates that the ME4054 is in a charge cycle.Once the charge cycle has terminated,the pin state is determined by undervoltage lockout conditions.A weak pull-down indicates that VCC meets the UVLO conditions and the ME4054 is ready to charge.High impedance indicates that t
28、he ME4054 is in undervoltage lockout mode:either VCC is less than 100mV above the BAT pin voltage or insufficient voltage is applied to the VCC pin.A microprocessor can be used to distinguish between these three statesthis method is discussed in the Applications Information section.Limiting An inter
29、nal thermal feedback loop reduces the programmed charge current if the die temperature attempts to rise above a preset value of approximately 120C.This feature protects the ME4054 from excessive temperature and allows the user to push the limits of the power handling capability of a given circuit bo
30、ard without risk of damaging the ME4054.The charge current can be set according to typical(not worst-case)ambient temperature with the assurance that the charger will automatically reduce the current in worst-case conditions.ThinSOT power considerations are discussed further in the Applications Info
31、rmation section.Lockout(UVLO)An internal undervoltage lockout circuit monitors the input voltage and keeps the charger in shutdown mode until VCC rises above the undervoltage lockout threshold.The UVLO circuit has a built-in hysteresis of 200mV.Furthermore,to protect against reverse current in the p
32、ower MOSFET,the UVLO circuit keeps the charger in shutdown mode if VCC falls to within 30mV of the battery voltage.If the UVLO comparator is tripped,the charger will not come out of shutdown mode until VCC rises 100mV above the battery voltage.Shutdown At any point in the charge cycle,the ME4054 can
33、 be put into shutdown mode by removing RPROG thus floating the PROG pin.This reduces the battery drain current to less than 2uA and the supply current to less than 50uA.A new charge cycle can be initiated by reconnecting the program resistor.In manual shutdown,the CHRG pin is in a weak pull-down sta
34、te as long as VCC is high enough to exceed the UVLO conditions.The CHRG pin is in a high impedance state if the ME4054 is in undervoltage lockout mode:either VCC is within 100mV of the BAT pin voltage or insufficient voltage is applied to the VCC pin.Recharge Once the charge cycle is terminated,the
35、ME4054 continuously monitors the voltage on the BAT pin using a comparator with a 2ms filter time(tRECHARGE).A charge cycle restarts when the battery voltage falls below (which corresponds to approximately 80%to 90%battery capacity).This ensures that the battery is kept at or near a fully charged co
36、ndition and eliminates the need for periodic charge cycle initiations.CHRG output enters a strong pull-down state during recharge cycle State Diagram of a Typical Charge Cycle Application Information Considerations The constant-voltage mode feedback loop is stable without an output capacitor provide
37、d a battery is connected to the charger output.With no battery present,an output capacitor is recommended to reduce ripple voltage(as.When using high value,low ESR ceramic capacitors,it is recommended to add a 1 resistor in series with the capacitor.No series resistor is needed if tantalum capacitor
38、s are used.In constant-current mode,the PROG pin is in the feedback loop,not the battery.The constant-current mode stability is affected by the impedance at the PROG pin.With no additional capacitance on the PROG pin,the charger is stable with program resistor values as high as 20K.However,additiona
39、l capacitance POWER ON TRICKLE CHARGE MODE 1/10TH FULL CURRENT BAT BAT PROG100mV CHARGE MODE FULL CURRENT CHRG:STRONG STANDBY MODE NO CHARGE CURRENT CHRG:WEAK SHUNDOWN MODE ICC DROPS TO25A CHRG:HI-Z IN UVLO PROG FLOATED OR on this node reduces the maximum allowed program resistor.The pole frequency
40、at the PROG pin should be kept above 100KHz.Therefore,if IPROG pin is loaded with a capacitance CPROG,the following equation should be used to calculate the maximum resistance value for RPROG：Average,rather than instantaneous,charge current may be of interest to the user.For example,if a switching p
41、ower supply operating in low current mode is connected in parallel with the battery,the average current being pulled out of the BAT pin is typically of more interest than the instantaneous current pulses.In such a case,a simple RC filter can be used on the PROG pin to measure the average battery cur
42、rent as shown in.A 10K resistor has been added between the PROG pin and the filter capacitor to ensure stability.Isolating Capacitive Load on PROG Pin and Filtering dissipation The conditions that cause the ME4054 to reduce charge current through thermal feedback can be approximated by considering t
43、he power dissipated in the IC.Nearly all of this power dissipation is generated by the internal MOSFET-this is calculated to be approximately:PD(VCC VBAT)*I BAT Where PD is the power dissipated,VCC is the input supply voltage,VBAT is the battery voltage and IBAT is the charge current.The approximate
44、 ambient temperature at which the thermal feedback begins to protect the IC is:TA 120C PDJA 120C(VCC VBAT)*IBAT*JA For example:The ME4054 with 5V supply voltage through programmable provides full limiting current 400mA to a charge lithium-ion battery with voltage.If JA is 150/W(reference to PCB layo
45、ut considerations),When ME4054 begins to decrease the charge current,the ambient temperature about:TA=120-*(400mA)*150/W=120*150/W=120-75=45 ME4054 can work in the condition of the temperature is above 45,the charge current is calculated to be approximately:ABATBATJA120-TI=(VCC-V)*Using the previous
46、 example with an ambient temperature of 60,the charge current will be reduced to approximately:BAT120-60I=320mA(5V-3.75V)*150/W Moreover,when thermal feedback reduces the charge current,the voltage at the PROG pin is also reduced proportionally as discussed in the operation section.It is important t
47、o remember that ME4054 applications do not need to be designed for worst-case thermal conditions since the IC will automatically reduce power dissipation when the junction temperature reaches approximately120.considerations Because of the small size of the thinSOT package,it is important to use a go
48、od thermal PC board layout to maximize the available charge current.The thermal path for the heat generated by the IC is from the die to the copper lead frame,through the package leads,(especially the ground lead)to the PC board copper.The PC board copper is the heat sink.The footprint copper pads s
49、hould be as wide as possible and expand out to larger copper areas to spread and dissipate the heat to the surrounding ambient.Other heat sources on the board,not related to the charger,must also be considered when designing a PC board layout because they will affect overall temperature rise and the
50、 maximum charge current.The following table lists thermal resistance for several different board sizes and copper areas.All measurements were taken in still air on2/32”FR-4 board with the device mounted on topside.Measured Thermal resistance(2-layer board:each layer uses one ounce copper Copper area