LP4054 ETC | Alldatasheet
Document overview
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Technical content
Features
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 with Thermal Regulation to Maximize Charge Rate Without Risk of Overheating Charges Single Cell Li-Ion Batteries Directly from USB Port Preset 4.2V Charge Voltage with ± 1% Accuracy Charge Current Monitor Output for Gas Gauging Automatic Recharge Soft-Start Limits Inrush Current Available in 5-Lead SOT-23 Package 2.9V Trickle Charge Threshold C/10 Charge Termination 25mA Supply Current in Shutdown 2.9V Trickle Charge Threshold
Applications
Portable Media Players/MP3 players Cellular and Smart mobile phone Charging Docks and Cradles Bluetooth Applications Marking Information Please see website. F:PB-Free
P r e l i m i n a r y LP4054 LP4054-datasheet V1.0 Sep.-2006 2-2 Typical Application Circuit LP4054 LP4054 LP4054 LP4054 LP4054
P r e l i m i n a r y LP4054 LP4054-datasheet V1.0 Sep.-2006 3-3 Functional Pin Description PIN LP4054 DESCRIPTION CHRG 1 Open-Drain Status Output GND 2 Ground BAT 3 Charge Current Output VCC 4 Positive Input Supply Voltage PROG 5 Charge Current Program, Charge Current Monitor and Shutdown Pin. Pin Functions CHRG (PIN 1): Open-Drain Charge Status Output. When the battery is charging, the CHRG pin is pulled low by an internal N-channel MOSFET. When the charge cycle is completed, a weak pull-down of approximately 12µA is connected to the CHRG pin, indicating a “AC pres ent” condition. When the LP4054 detects an undervolta ge lockout condition, CHRG is forced high impedance. GND (PIN 2): Ground. BAT (PIN 3): Charge Current Output. Provides charge current to the ba ttery and regulates the final float voltage to 4.2V. An internal precision resistor divider from this pin sets the float voltage which is disconnected in shutdown mode. VCC (PIN 4): Positive Input Supply Voltage. Prov ides power to the charger. V CC can range from 4.35V to 6.5V and should be bypassed with at l east a 1µF capacitor. When V CC drops to within 30mV of the BAT pin voltage, the LP4054 enters shutdown mode, dropping IBAT to less than 2µA. PROG (PIN 5): Charge Current Program, Charge Current Monito r and Shutdown Pin. The charge current is programmed by connecting a 1% resistor, RPROG, to ground. When charging in constant-current mode, this pin servos to 1V. In all modes, the voltage on this pin can be used to measure the charge current using the following formula: The PROG pin can also be used to shutdown the charger. Disconnecting the program resistor from ground allows a 3µA current to pull the PROG pin high. When it reaches the 1.94V shutdown threshold voltage, the charger enters shutdown mode, charging stops and t he input supply current drops to 25µ A. This pin is also clamped to approximately 2.4V. Driving th is pin to voltages beyond t he clamp voltage will draw currents as high as1.5mA. Reconnecting RPROG to ground will return the charger to normal operation. LP4054 (TSOT23-5)
P r e l i m i n a r y LP4054 LP4054-datasheet V1.0 Sep.-2006 4-4 Function Block Diagram Absolute Maximum Ratings
P r e l i m i n a r y LP4054 LP4054-datasheet V1.0 Sep.-2006 5-5 Electrical Characteristics (Over 0C ≤TJ ≤125°C and recommended supply voltage) Note 1: Absolute Maximum Ratings are those values beyond which the life of the device may be impaired. Note 2: The LP4054 are guaranteed to meet performance specifications from 0℃ to 70 ℃. Specifications over the -40℃ to 85 ℃ operating temperature range are assured by design, characterization and correlation with statistical process controls. Note 3: See Thermal Considerations. Note 4: Supply current includes PROG pin current (approximately 100µA) but does not include any current delivered to the battery through the BAT pin (approximately 100mA). Note 5: This parameter is not applicable to the LP4054X. Note 6: I TERM is expressed as a fraction of measured full charge current with indicated PROG resistor.
P r e l i m i n a r y LP4054 LP4054-datasheet V1.0 Sep.-2006 6-6 Typical Operating Characteristics
P r e l i m i n a r y LP4054 LP4054-datasheet V1.0 Sep.-2006 7-7
P r e l i m i n a r y LP4054 LP4054-datasheet V1.0 Sep.-2006 8-8
P r e l i m i n a r y LP4054 LP4054-datasheet V1.0 Sep.-2006 9-9 Operation The LP4054 is a single cell lithium-ion battery charger using a constant-current/c onstant-voltage algorithm. It can deliver up to 800mA of charge current (using a good thermal PCB layout) with a final float voltage accuracy of ± 1% . The LP4054 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. Furthermore, the LP4054 is capable of oper ating from a USB power source. Normal Charge Cycle A charge cycle begins w hen the voltage at the V CC 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 pin is less than 2.9V, the charger enters trickle charge mode. In this mode, the LP4054 supplies approximately 1/10 the programmed charge current to bring the battery voltage up to a safe level for full current charging. (N ote: The LP4054X does not include this trickle charge feature). When the BAT pin voltage rises above 2.9V, the charger enters constant-c urrent mode, where the programmed charge current is supplied to the battery. When the BAT pin approaches the final float voltage (4.2V), the LP4054 enters c onstant-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. Programming Charge Current The charge current 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: The charge current out of the BAT pin can be determined at any time by monitoring the PROG pin voltage using the following equation: Charge 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 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 cu rrent is latched off and the LP4054 enters standby mode, where the input supply current drops to 200µA. 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 (T TERM) on the termination com parator ensures that transient loads of this natur e do not result in premature charge cycle termination. Once the average charge current drops below 1/10th the programmed value, the LP4054 terminates the char ge cycle and ceases to provide any current through the BAT pin. In this state, all loads on the BAT pin must be supplied by the battery. The LP4054 constantly monitors the BAT pin voltage in standby mode. If this voltage drops below the 4.05V recharge threshold (V RECHRG), 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 voltage must be removed and reapplied, or the charger must be shut down and restarted using the PROG pin. Figure 7 show s the state diagram of a typical charge cycle. Charge Status Indicator(CHRG) The charge status output has three different states: strong pull-down(~10mA), weak pull-down (~12µA) and high impedance. The strong pu ll-down state indicates that the LP4054 is in a char ge cycle. Once the charge cycle has terminated , the pin state is determined by undervoltage lockout conditions. A weak pull-down indicates that V CC meets the UVLO conditions and the LP4054 is ready to charge. High impedance indicates that the LP4054 is in undervoltage lockout mode: either VCC is less than 100mV above the BAT pin voltage or insufficient voltage is applied to the V CC pin. A microprocessor can be used to distinguish between
P r e l i m i n a r y LP4054 LP4054-datasheet V1.0 Sep.-2006 10-10 these three states –this method is discussed in the Applications Information section. Charge Termination An internal thermal feedback loop reduces the programmed charge current if the die temperature attempts to rise above a preset value of approximately 120℃. This feature protects the LP4054 from excessive temperature and allows the user to push the limits of the power handling capability of a given circuit board without risk of damaging the LP4054. 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 Information section. Undervoltage Lockout (UVLO) An internal undervoltage lockout circuit monitors the input voltage and keeps the charger in shutdown mode until V CC rises above the undervoltage lockout threshold .The UVLO circuit has a built-in hysteresis of 200mV. Furthermore, to protect against reverse current in the power MOSFET, the UVLO circuit keeps the charger in shutdown mode if V CC falls to within 30mV of the battery voltage. If the UV LO comparator is tripped, the charger will not come out of shutdown mode until VCC rises 100mV above the battery voltage. Manual Shutdown At any point in the charge cycle, the LP4054 can be put into shutdown mode by removing RPROG thus floating the PROG pin. This reduces the battery drain current to less than 2µA and the supply current to less than 50µA. A new charge cycle can be initiated by reconnecting the program resistor. In manual shutdown, the CHRG pin is in a weak pull-down state as long as VCC is high enough to exceed the UVLO conditions. The CHRG pin is in a high impedance state if the LP 4054 is in under voltage lockout mode: either VCC is within 100mV of the BAT pin voltage or insufficient vo ltage is applied to the VCC pin. Automatic Recharge Once the charge cycle is terminated, the LP4054 continuously monitors the voltage on the BAT pin using a comparator with a 2ms filter time (T RECHARGE). A charge cycle restarts when the battery voltage falls below 4.05V (which corres ponds to approximately 80% to 90% battery capacity). This ensures that the battery is kept at or near a fu lly charged condition and eliminates the need for periodic charge cycle initiations. CHRG output enters a strong pull-down state during recharge cycles.
Application Information
The constant-voltage mode feedback loop is stable without an output capacitor provided a battery is connected to the charger output. With no battery present, an output capacitor is recommended to reduce ripple voltage. When using high value, low ESR ceramic capacitors, it is recommended to add a 1 Ω resistor in series with the capacitor. No series resistor is needed if tantalum capacitors are used. In constant-current mode, the PROG pin is in the feedback loop, not the battery. The constant-current mode st ability is affected by the impedance at the PROG pi n. With no additional capacitance on the PROG pin, the charger is stable with program resistor values as high as 20k. However,
at the PROG pin should be kept above 100kHz. discharged Li-Ion battery wi th a voltage of 3.75V. board layout to maximize the available charge current. board copper. The PC board co pper is the heat sink. Figure 8. Isolating Capacitive Load on PROG Pin and Filtering
P r e l i m i n a r y LP4054 LP4054-datasheet V1.0 Sep.-2006 12-12 possible and expand out to larger copper areas to spread and dissipate the heat to the surrounding ambient. Feedthrough vias to inner or backside copper layers are also useful in improving the overall thermal performance of the charger .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 maximum charge current. Increasing Thermal Regulation Current Reducing the voltage drop across the internal MOSFET can significantly decrease t he power dissipation in the IC. This has the effect of increasing the current delivered to the battery during thermal regulation. One method is by dissipating some of the power through an external component, such as a resistor or diode. Example: An LP4054 operati ng from a 5V wall adapter is programmed to supply 800mA full-scale current to a discharged Li-Ion battery wi th a voltage of 3.75V. Assuming θ JA is 125 ℃/W, the approximate charge current at an ambient temperature of 25℃ is: By dropping voltage across a resistor in series with a 5V wall adapter (shown in Figure 9), the on-chip power dissipation can be decreased, thus increasing the thermally regulated charge current.: Solving for IBAT using the quadratic formaula Using RCC = 0.25Ω, VS = 5V, VBAT = 3.75V, TA = 25℃ and θJA = 125℃/W we can calculate the thermally regulated charge current to be: While this application delivers more energy to the battery and reduces charge time in thermal mode, it may actually lengthen char ge time in voltage mode if VCC becomes low enough to put the LP4054 into dropout. This technique works best when RCC values are minimized to keep compone nt size small and avoid dropout. Remember to choose a resistor with adequate power handling capability. VCC Bypass Capacitor Many types of capacitor s can be used for input bypassing, however, caution must be exercised when using multilayer ceramic c apacitors. Bec ause of the self-resonant and high Q characteristics of some types of ceramic capacitors, hi gh voltage transients can be generated under some start-up conditions, such as connecting the charger input to a live power source .Adding a 1.5 Ω resistor in series with an X5R ceramic capacitor will minimize start-up voltage
P r e l i m i n a r y LP4054 LP4054-datasheet V1.0 Sep.-2006 13-13 transients. Charge Current Soft-Start The LP4054 includes a soft-start circuit to minimize the inrush current at the start of a charge cycle. When a charge cycle is initiated, t he charge current ramps from zero to the full-scale current over a period of approximately 100µs. This has the effect of minimizing the transient current load on the power supply during start-up. CHRG Status Output Pin The CHRG pin can provide an indication that the input voltage is greater than the undervoltage lockout threshold level. A weak pull-down current of approximately 12µA indicates t hat sufficient voltage is applied to VCC to begin charging. When a discharged battery is connected to the charger, the constant current portion of the charge cycl e begins and the CHRG pin pulls to ground. The CHRG pin can sink up to 10mA to drive an LED that indicates that a charge cycle is in progress. When the battery is nearing full charge, the charger enters the constant -voltage portion of the charge cycle and the charge current begins to drop. When the charge current drops below 1/10 of the programmed current, the charge cycle ends and the strong pull-down is replaced by the 12µA pull-down, indicating that the charge cycle has ended. If the input voltage is removed or drops below the under voltage lockout threshold, t he CHRG pin becomes high impedance. Figure 10 shows that by using two different value pull-up resistors, a micro-processor can detect all three states from this pin. To detect when the LP4054 is in charge mode, force the digital output pin (OUT) hi gh and measure the voltage at the CHRG pin. The N-c hannel MOSFET will pull the pin voltage low even with t he 2k pull-up resistor. Once the charge cycle terminates, the N-channel MOSFET is turned off and a 12µA current source is connected to the CHRG pin. The IN pin will then be pulled high by the 2k pull-up resistor. To determine if there is a weak pull-down current, the OUT pin should be forced to a high impedance state. The weak current source will pull the IN pin low through the 800k resistor; if CHRG is high impedance, the IN pin will be pulled high, indicating that the part is in a UVLO state. Reverse Polarity Input Voltage Protection In some applications, protec tion from reverse polarity voltage on VCC is desired .If t he supply voltage is high enough, a series blocking di ode can be used. In other cases, where the voltage drop must be kept low a P-channel MOSFET can be used (as shown in Fig 11.) USB and Wall Adapter Power The LP4054 allows charging from both a wall adapter and a USB port. Figure 12 shows an example of how to combine wall adapter and USB power inputs. A P-channel MOSFET, MP1,is used to prevent back conducting into the USB por t when a wall adapter is present and a Schottky diode, D1, is used to prevent USB power loss through the 1k pull-down resistor. Typically a wall adapter can supply more current than the 500mA-limited USB port. T herefore, an N-channel MOSFET, MN1, and extra 10k program resistor are used to increase the charge current to 600mA when the wall adapter is present.
P r e l i m i n a r y LP4054 LP4054-datasheet V1.0 Sep.-2006 14-14 Packaging Information