Preliminary Datasheet LP28300 2A Synchronous Buck Li-ion Charger General Description Features The LP28300 is a 2A Li-Ion battery charger intended for5V wall adapters. It utilizes a 1.5MHz synchronous buck converter topology to reduce power dissipation during charging. Low power dissipation, an internal MOSFET allow a physically small charger that can be embedded in a wide range of handheld applications. The LP28300 includes complete charge termination circuitry, automatic recharge and a ±1% 4.2V float voltage. Input short-circuit protection is included so no blocking diode is required. ¾ ¾ ¾ ¾ Battery charge current, charge timeout and end-of-charge indication parameters are set with external components. Additional features include shorted cell detection, temperature qualified charging and overvoltage protection. The LP28300 is available in a low profile (0.75mm) 10-lead(3mm × 3mm) DFN package. ¾ ¾ ¾ ¾ ¾ Order Information LP28300 - □ □ Very Low Power Dissipation 2A Maximum Charge Current No External MOSFETs and Blocking Diode Required 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 Drainage Charge Current Thermal Regulation Status Outputs for LED or System Interface Optional Battery Temperature Monitoring Before and During Charge Automatic Sleep Mode for Low-Power Consumption Available in 3mm × 3mm TDFN-10 Package RoHS Compliant and 100% Lead (Pb)-Free Typical Application Circuit □ F: Pb-Free Package Type QV: TDFN-10 Applications Portable Media Players Cellular and Smart mobile phone PDA/DSC Handheld Battery-Powered Devices Handheld Computers Charging Docks and Cradles Marking Information Please see website. LP28300 – 01 Version 1.1 Datasheet Sep.-2010 www.lowpowersemi.com Page 1 of 10 Preliminary Datasheet LP28300 Functional Pin Description P a c k a g e Ty p e Pin Configurations VIN 1 TS 2 EN 3 STAT 4 BATT 5 10 GND 9 SW 8 NC 7 VIN 6 SNS LP28300 TDFN- 10 11 PGND Pin Description PIN PIN Number VIN 1,7 TS 2 EN 3 STAT 4 BATT 5 SNS 6 NC 8 SW 9 GND PGND 10 11 LP28300 – 01 Version DESCRIPTION Positive Supply Voltage Input. This pin connects to the power devices inside the chip. VIN ranges from 4V to 5.5V for normal operation. Operation down to the under-voltage lockout threshold is allowed with current limited wall adapters. Decouple with a 10µF or larger surface mounted ceramic capacitor. NTC (Negative Temperature Coefficient) Thermistor Input. With an external 10kΩ NTC thermistor to ground, this pin senses the temperature of the battery pack and stops the charger when the temperature is out of range. To disable the temperature qualification function, ground the NTC pin. Enable Input Pin. Pulling the EN pin high places the LP28300 into a low power state where the BAT drain current drops to less than 3µA and the supply current is reduced to less than 50µA. For normal operation, pull the pin low. Open-Drain Charge Status Output. When the battery is charging, the STAT pin is pulled low by an internal N-channel MOSFET. When the charge cycle is completed, When the LP28300 detects an under voltage lockout condition, STAT is forced high impedance. Battery Charger Output Terminal. Connect a 22µF ceramic chip capacitor between BAT and PGND to keep the ripple voltage small. Internal Sense Resistor. Connect to external inductor. Current Amplifier Sense Input. A sense resistor, RSENSE, must be connected between the SENSE and BAT pins. The maximum charge current is equal to 100mV/RSENSE. No connector. Switch Node Connection. This pin connects to the drains of the internal main and synchronous power MOSFET switches. Connect to external inductor. Ground. Power Ground Pad. 1.1 Datasheet Sep.-2010 www.lowpowersemi.com Page 2 of 10 Preliminary Datasheet LP28300 Typical Application Circuits VIN 1 VIN 7 3 VIN EN 4 1R LP28300 SNS 10 VIN 1 1R LP28300 STAT 10 BATT 10uH 6 SNS RSNS 100mR 5 2 TS PGND GND 10uF 1Cell 9 BATT 10uF 22uF Rts 10K 11 SW VIN EN 4 2 1uF VIN 7 3 RSNS 100mR 5 TS PGND 10uF 10uH 6 BATT STAT GND 10uF 9 SW 22uF 1uF 11 BATT Rts 10K USB Charge CTRL H:USB Charging, Iset=500mA L:DC Adapter Charging, Iset=1300mA VIN 1 7 3 VIN VIN EN 1R 4 SW LP28300 STAT BATT 10uF 10 Version 1.1 Datasheet Sep.-2010 PGND GND 10uF LP28300 – 01 SNS TS RSNS1 100mR Q1 9 6 10uH RSNS2 200mR 5 1uF 22uF 2 11 www.lowpowersemi.com Rts 10K BATT Page 3 of 10 Preliminary Datasheet LP28300 Function Block Diagram GND Vin SW SNS Vin EN GND BATT STAT Absolute Maximum Ratings Input Voltage to GND (VIN) ----------------------------------------------------------------------------- 2.6V to 6.5V BAT, ISET, STAT (VX) ------------------------------------------------------------------------ 0.3V to VIN+0.3V BAT Short-Circuit Duration ---------------------------------------------------------------------------- Continuous BAT Pin Current ------------------------------------------------------------------------------------------ 2500mA Maximum Junction Temperature ---------------------------------------------------------------------------- 125°C Operating Junction Temperature Range (TJ) ----------------------------------------------------- -40℃ to 85°C Maximum Soldering Temperature (at leads, 10 sec) ------------------------------------------------------ 260°C Thermal Information Maximum Power Dissipation (PD,TA<40°C) -------------------------------------------------------------- 2W Thermal Resistance (JA) ---------------------------------------------------------------------------------- 46℃/W LP28300 – 01 Version 1.1 Datasheet Sep.-2010 www.lowpowersemi.com Page 4 of 10 Preliminary Datasheet LP28300 Electrical Characteristics (The specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, unless otherwise noted.) SYMBOL VIN PARAMETER Adapter/USB Voltage Range ICC VFLOAT CONDITIONS Input Supply Current Regulated Output (Float) Voltage Charge Mode (Note 4), RISET = 10k Standby Mode (Charge Terminated) Shutdown Mode (RISET Not Connected, VCC < VBAT, or VCC < VUV) 0°C ≤ TA ≤ 85°C, IBAT = 40mA RSNS = 100mΩ, Current Mode RSNS = 68mΩ, Current Mode IBAT MIN 2.65 4.158 860 1300 0 BAT Pin Current Standby Mode, VBAT = 4.2V Shutdown Mode (RISET Not Connected) Sleep Mode, VCC = 0V ITRIKL Trickle Charge Current VTRIKL Trickle Charge Threshold Voltage VTRHYS Trickle Charge Hysteresis Voltage VBAT < VTRIKL, RSNS = 100mΩ(Note 80 5) RSNS = 100mΩ,VBAT Rising (Note 5) 2.8 RSNS = 100mΩ,(Note 5) 60 VSNS ISTAT SNS Pin Voltage STAT Pin Weak Pull-Down Current RISET = 10k, Current Mode VSTAT = 5V VSTAT STAT Pin Output Low Voltage ISTAT = 5mA ΔVRESTAT TLIM TSS ISNS LP28300 – 01 Recharge Battery Threshold Voltage VFLOAT - VRESTAT Junction Temperature in Constant Temperature Mode Soft-Start Time IBAT = 0 to IBAT =850V/RISET ISET Pin Pull-Up Current Version 1.1 Datasheet Sep.-2010 www.lowpowersemi.com 88 8 100 TYP. 5 MAX UNITS 6 V 300 2000 200 500 25 4.2 1000 1470 -2.5 ±1 ±1 100 2.9 80 100 20 0.35 150 50 4.242 1120 1620 -6 ±2 ±2 120 3.0 110 116 35 0.6 200 120 uA V mA uA mA V mV mV uA V mV 100 3 °C uS uA Page 5 of 10 Preliminary Datasheet LP28300 Typical Operating Characteristics LP28300 – 01 Version 1.1 Datasheet Sep.-2010 www.lowpowersemi.com Page 6 of 10 Preliminary Datasheet LP28300 Operation The LP28300 is a constant current, constant voltage Li-Ion battery charger controller that uses a current mode PWM step-down (buck) switching architecture. The charge current is set by an external sense resistor (RSENSE) across the SENSE and BAT pins. The final battery float voltage is internally set to 4.2V per cell. For batteries like lithium-ion that require accurate final float voltage, the internal 2.4V reference, voltage amplifier and the resistor divider provide regulation with ±1% accuracy. Figure 1.Typical Charge Profile A charge cycle begins when the voltage at the VCC pin rises above the UVLO level and is 250mV or more greater than the battery voltage. At the beginning of the charge cycle, if the battery voltage is less than the trickle charge threshold, 2.9V for the 4.2 version, the charger goes into trickle charge mode. The trickle charge current is internally set to 15% of the full-scale current. If the battery voltage stays low for 30 minutes, the battery is considered faulty and the charge cycle is terminated. When the battery voltage exceeds the trickle charge threshold, the charger goes into the full-scale constant current charge mode. In constant current mode, the charge current is set by the external sense resistor RSENSE and an internal 100mV reference; start to decrease. When the current drops to 25% of the full-scale charge current, an internal comparator turns off the internal pull-down N-channel MOSFET at the STAT pin, and connects a weak current source to ground to indicate a near end-of-charge condition. A 10kΩ NTC (negative temperature coefficient) thermistor can be connected from the NTC pin to ground for battery temperature qualification. The charge cycle is suspended when the temperature is outside of the 0°C to 50°C window. Shutdown The LP28300 can be shut down by pulling the COMP pin to ground which pulls the GATE pin high turning off the external P-channel MOSFET. When the COMP pin is released, the internal timer is reset and a new charge cycle starts. In shutdown, the output of the CHRG pin is high impedance and the quiescent current remains at 1.5mA. Removing the input power supply will put the charger into sleep mode. If the voltage at the VCC pin drops below (VBAT + 250mV) or below the UVLO level, the LP28300 goes into a low current (ICC = 10µA) sleep mode, reducing the battery drain current. Automatic Recharge Once the charge cycle is terminated, the LP28300 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 4.05V (which corresponds to approximately 80% to 90% battery capacity). This ensures that the battery is kept at or near a fully charged condition and eliminates the need for periodic charge cycle initiations. STAT output enters a strong pull-down state during recharge cycles. When the battery voltage approaches the programmed float voltage, the charge current will Battery Temperature Detection A negative temperature coefficient (NTC) thermistor located close to the battery pack can be used to monitor battery temperature and will not allow charging unless the battery temperature is within an acceptable range. Connect a 10kΩ thermistor from the TS pin to ground. If the LP28300 – 01 www.lowpowersemi.com Version 1.1 Datasheet Sep.-2010 Page 7 of 10 Preliminary Datasheet LP28300 temperature rises to 50°C, the resistance of the one-half of output charge current. Actual NTC will be approximately 4.2kΩ. With the 85µA pull-up current source, the Hot temperature voltage threshold is 360mV. For Cold temperature, the voltage threshold is set at 2.4V which is equal to 0°C (Rts 28kΩ) with 85µA of pull-up current. If the temperature is outside the window, the GATE pin will be pulled up to VCC and the timer frozen while the output status at the STAT pin remains the same. The charge cycle begins or resumes once the temperature is within the acceptable range. Short the TS pin to ground to disable the temperature qualification feature. However the user may modify these thresholds by adding two external resistor. See figure 3. capacitance value is not critical. Solid tantalum capacitors have a high ripple current rating in a relatively small surface mount package, but caution must be used when tantalum capacitors are used for input bypass. High input surge currents can be created when the adapter is hot-plugged to the charger and solid tantalum capacitors have a known failure mechanism when subjected to very high turn-on surge currents. Selecting the highest possible voltage rating on the capacitor will minimize problems. Consult with the manufacturer before use. The selection of output capacitor COUT is primarily determined by the ESR required to minimize ripple voltage and load step transients. The output ripple ∆VOUT is approximately bounded by: Figure 2. Temperature Sensing Configuration Since ∆IL increases with input voltage, the output ripple is highest at maximum input voltage. Typically, once the ESR requirement is satisfied, the capacitance is adequate for filtering and has the necessary RMS current rating. Switching ripple current splits between the battery and the output capacitor depending on the ESR of the output capacitor and the battery impedance. EMI considerations usually make it desirable to minimize ripple current in the battery leads. Ferrite beads or an inductor may be added to increase battery impedance at the 500kHz switching frequency. If the ESR of the output capacitor is 0.2Ω and the battery impedance is raised to 4Ω with a bead or inductor, only 5% of the current ripple will flow in the battery. Figure 3. Temperature Sensing Thresholds Input and Output Capacitors Since the input capacitor is assumed to absorb all input switching ripple current in the converter, it must have an adequate ripple current rating. Worst-case RMS ripple current is approximately Inductor Selection A high (1.5MHz) operating frequency was chosen for the buck switcher in order to minimize the size of the inductor. However, take care to use inductors with low core losses at this frequency. A good LP28300 – 01 www.lowpowersemi.com Version 1.1 Datasheet Sep.-2010 Page 8 of 10 Preliminary Datasheet choice is the IHLP-2525AH-01from Vishay Dale. LP28300 typical application. With 1.5µH and2A charge current: To calculate the inductor ripple current: and where VBAT is the battery voltage, VIN is the input voltage, L is the inductance and f is the PWM oscillator frequency(typically 1.5MHz). Maximum inductor ripple current occurs at maximum VIN and VBAT = VIN/2. Layout Considerations Peak inductor current will be: where IBAT is the maximum battery charging current. When sizing the inductor make sure that the peak current will not exceed the saturation current of the inductors. Also, ∆IL should never exceed 0.4(IBAT) as this may interfere with proper operation of the output short-circuit protection comparator. 1.5µH provides reasonable inductor ripple current in a LP28300 – 01 Version 1.1 Datasheet Sep.-2010 Switch rise and fall times are kept under 5ns for maximum efficiency. To minimize radiation, the SW pin and input bypass capacitor leads (between VIN and PGND) should be kept as short as possible. A ground plane should be used under the switching circuitry to prevent inter plane coupling. The exposed pad must be connected to the ground plane for proper power dissipation. The other paths contain only DC and/or 1.5MHz tri-wave ripple current and are less critical. With the exception of the input and output filter capacitors(which should be connected to PGND) all other components that return to ground should be connected to GND. www.lowpowersemi.com Page 9 of 10 Preliminary Datasheet LP28300 Packaging Information LP28300 – 01 Version 1.1 Datasheet Sep.-2010 www.lowpowersemi.com Page 10 of 10