LP78073A POWER | Alldatasheet
Document overview
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Technical content
Features
Charger: Programmable Charge Current Up to 1000mA No MOSFET, Sense Resistor or 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 8µA Supply Current in Shutdown Drainage Charge Current Thermal Regulation Status Outputs for LED or System Interface Boost: 5V/1.2A Output Current @ Vin=3.3V 1MHz fixed frequency switching High Switch On Current: 2.7A Low RDS(ON) Integrated Power Mosfet Efficiency is 95% Built-in OTP, OCP, Soft-Star Consumption Available in ESOP-8 Package RoHS Compliant and 100% Lead (Pb)-Free
Applications
MID/Pad Power Bank Smart Phone Bluetooth Applications Marking Information Device Marking Package Shipping LP78073ASPF SP:ESOP-8 2.5K/REEL
LP78073A-01 Jun.-2015 Email: marketing@lowpowersemi.com www.lowpowersemi.com Page 2 of 10 Preliminary Datasheet LP78073A Functional Pin Description Package Type Pin Configurations ESOP-8 FB BAT VOUT EN ISET CHRG_B LX VIN 4 5 GND Pin Description PIN NAME DESCRIPTION 1 FB Boost Feedback pin. The pin voltage is 0.8V. 2 LX Boost Output switching node. SW is the drain of the internal low -side N -Channel MOSFET and high -side P-Channel MOSFET. Connect the inductor to SW to Complete the step-up converter.
3 CHRG_B
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, the pin is pulled High.
4 ISET
Charge Current Program, Charge Current Monitor and Shutdown Pin. The charge current is pro grammed by connecting a 1% resistor (RPROG)to ground. When charging in constant-current mode, this pin servos to 2V. In all modes, the voltage on this pin can be used to measure the charge current using the following formula.LP78073A: Iset=1000/RPROG. 5 Vin VIN is the input power source. Connect to a wall adapter. 6 BAT BAT is the connection to the battery. A 10µF capacitor is needed at least. 7 VOUT Output voltage pin. 8 EN Boost enable pin. Active High. 9 GND Ground Pin. Application Circuit BAT CHRG_B VOUTVIN GND ISET Rset Cin 10uF Cbat 10uF LP78073A LXEN 2.2uH FB Cout 10uF 68K 13K 20pF/NC Vout Battery VIN LED ON OFF 10Ω 2.2nF
LP78073A-01 Jun.-2015 Email: marketing@lowpowersemi.com www.lowpowersemi.com Page 3 of 10 Preliminary Datasheet LP78073A Function Block Diagram TA 145℃ TDIE CA MA VA REF 1.22V CHRG_B SHDN TO BAT 2.9V VCC 3μA 0.1V ISET BAT VCC 5μA 1200X1X ENEN FB REF VOUT LX VHIGH SLOPE COMPENSATION CURRENT SENSE CURRENT LIMIT INTERNAL COMPENSATION CONTROL LOGIC OSC BODY AND VHIGH SELECT ZCD+ + GND 4 9 VIN
LP78073A-01 Jun.-2015 Email: marketing@lowpowersemi.com www.lowpowersemi.com Page 4 of 10 Preliminary Datasheet LP78073A Absolute Maximum Ratings Note 1 Note 1. Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Thermal Information ESD Susceptibility
LP78073A-01 Jun.-2015 Email: marketing@lowpowersemi.com www.lowpowersemi.com Page 5 of 10 Preliminary Datasheet LP78073A
Electrical Characteristics
(TA = 25°C. VIN = 5V, unless otherwise noted.) SYMBOL PARAMETER CONDITIONS MIN TYP. MAX UNITS Charge VIN Adapter/USB Voltage Range 4 5 6 V Iin Input Supply Current Charge Mode, RISET = 10k 300 2000 uA Standby Mode (Charge Terminated) 200 500 Shutdown Mode (RISET Not Connected, VIN < VBAT, or VIN < VUV) 25 50 VFLOAT Regulated Output (Float) Voltage 0°C ≤ TA ≤ 85°C, IBAT = 40mA 4.158 4.2 4.242 V IBAT BAT Pin Current RISET = 1k, Current Mode 1000 mA RISET = 2k, Current Mode 500 Standby Mode, VBAT = 4.2V,EN=High Shutdown Mode (RISET Not Connected) Sleep Mode, VIN = 0V ,EN=0V -200 -260 uA ITRIKL Trickle Charge Current VBAT < VTRIKL, RISET = 2k 50 mA VTRIKL Trickle Charge Threshold Voltage RISET = 10k, VBAT Rising 2.8 2.9 3.0 V VTRHYS Trickle Charge Hysteresis Voltage RISET = 10k 120 mV VUV VIN Under voltage Lockout Threshold From VIN Low to High 3.9 V VUVHYS VIN Under voltage Lockout Hysteresis 150 200 300 mV VASD VIN – VBAT Lockout Threshold Voltage VIN from Low to High 70 100 140 mV VIN from High to Low 5 30 50 mV ITERM C/10 Termination Current Threshold RISET = 10k 10 %IBAT RISET = 2k 10 %IBAT VISET ISET Pin Voltage RISET = 10k, Current Mode 2 V VSTAT STAT Pin Output Low Voltage ISTAT = 5mA 0.35 0.6 V ΔVRESTAT Recharge Battery Threshold Voltage VFLOAT - VRESTAT 100 150 200 mV TLIM Junction Temperature in Constant Temperature Mode 150 °C RON Power FET “ON” Resistance (Between VIN and BAT) 300 mΩ Boost(VBAT=3.5V, Vout=5V, TA=25℃) Vout Output Voltage Range 2.5 5.4 V UVLO UVLO 1.5 2.5 V Vfb Feedback Voltage 784 800 816 mV Ifb Feedback Input Current VFB=0.8V 50 nA Fosc Switching Frequency 1000 KHz Duty Maximum Duty Cycle 80 90 95 % VENL EN Input Low Voltage 0.4 V VENH EN Input High Voltage 1.4 V ILimit Low-side Current Limit 2.7 3 A Rds(on) High-side On Resistance Vout=3.3V 110 mΩ Low-side On Resistance 70 mΩ
LP78073A-01 Jun.-2015 Email: marketing@lowpowersemi.com www.lowpowersemi.com Page 6 of 10 Preliminary Datasheet LP78073A Typical Operating Characteristics Vout=5V, Vin=3V, Iout=2mA, CH1=LX,CH2=△VOUT Vout=5V, Vin=3V, Iout=100mA， CH1=LX,CH2=△VOUT Vout=5V, Vin=3V, Iout=500mA, CH1=LX,CH2=△VOUT Vout=5V, Vin=3V, Iout=1A， CH1=LX,CH2=△VOUT
LP78073A-01 Jun.-2015 Email: marketing@lowpowersemi.com www.lowpowersemi.com Page 7 of 10 Preliminary Datasheet LP78073A Charge Characteristics
LP78073A-01 Jun.-2015 Email: marketing@lowpowersemi.com www.lowpowersemi.com Page 8 of 10 Preliminary Datasheet LP78073A
Application Information
The LP78073A is a single cell lithium -ion battery charger using a constant -current/constant-voltage algorithm. It can deliver up to 1000mA of charge current (using a good thermal PCB layout) with a final float voltage accuracy of ±1%. The LP78073A 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 com ponents. Furthermore, the LP78073A is capable of operat ing from a USB power source. For boost function, LP78073Awill stay in PSM(Pulse Skipping Modulation) mode when there is a light load. This could reduce unnecessary dissipation to promote efficiency. When the load grow to a certain level the boost circuit would turn to PWM mode gradually. Normal Charge Cycle A charge cycle begins when the voltage at the VIN pin rises above the UVLO threshold level and a 1% ISET ram resistor is connected from the ISET 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 LP78073A supplies approximately 1/10 the ISET rammed charge current to bring the battery volt age up to a safe level for full current charging. When the BAT pin voltage rises above 2.9V, the charger enters constant -current mode, where the ISET rammed charge current is supplied to the battery. When the BAT pin approaches the final float voltage (4.2V), th e LP78073A enters constant-voltage mode and the charge current begins to decrease. When the charg e current drops to 1/10 of the ISET rammed value, the charge cycle ends. ISET ramming Charge Current The charge current is ISET rammed using a single resisto r from the ISET pin to ground. The battery charge current is 500 times the current out of the ISET pin. The ISET ram resistor and the charge current are calculated using the following equations: LP78073A: RSET=1000V/ICHG，ICHG= 1000V/RSET The charge current out of the BAT pin can be determined at any time by monitoring the ISET pin voltage using the following equation: IBAT= VSET x 500/RSET Note: Vset is 2Volts. Charge Termination When charging, transient loads on the BAT pin can cause the ISET pin to fall below 200mV for short periods of time before the DC charge current has dropped to 1/10th the ISET rammed value. The 1ms filter time (t TERM) on the termination comparator ensures that transient loads of this nature do not result in premature charge cycle termi nation. Once the average charge current drops below 1/10th the ISET rammed value, the LP78073A terminates the charge 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 LP78073A constantly monitors the BAT pin voltage in standby mode. If this voltage drops below the 4.05V recharge threshold (VRESTAT), another charge cycle be gins 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 ISET pin. Charge Status Indicator (STAT) The charge status output has two different states: st rong pull-down (~10mA) and high impedance. The strong pull-down state indicates that the LP78073A is in a charge cycle. Once the charge cycle has terminated, the pin state is determined by under voltage lockout conditions. High impedance indicates that the LP78073A is in under voltage lockout mode: either VIN is less than 100mV above the BAT pin voltage or insufficient voltage is applied to the VIN pin.
LP78073A-01 Jun.-2015 Email: marketing@lowpowersemi.com www.lowpowersemi.com Page 9 of 10 Preliminary Datasheet LP78073A Thermal Limiting An internal thermal feedback loop reduces the ISET rammed charge current if the die temperature attempts to rise above a preset value of approximately 150°C. This feature protects the LP78073A from excessive temperature and allows the user to push the limits of the power handling capability of a given circuit board without risk of damagi ng the LP78073A. 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. Automatic Recharge Once the charge cycle is termina ted, the LP78073A continu - ously 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 capac ity). 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. Boost Under voltage Lockout (UVLO) An internal under voltage lockout circuit monitors the input voltage is 2.5V and keeps the charger in shutdown mode until VIN rises above the under voltage lockout threshold. The UVLO circuit has a built -in hysteresis of 500mV.Furthermore, to protect against reverse c urrent in the power MOSFET, the UVLO circuit keeps the charger in shutdown mode if VIN falls to within 30mV of the battery voltage. If the UVLO comparator is tripped, the charger will not come out of shutdown mode until VIN rises 100mV above the battery voltage. BOOST Output voltage Setting Set the output voltage by selecting the resistive voltage divider ratio. The voltage divider drops the output voltage to the 0.8V feedback voltage. Use a 100K resistor for R2 of the voltage divider. Determine the high-side resistor R1 by the equation: Vout=(R1/R2+1) x VFB Vout=(R1/R2+1) x 0.8V Power Dissipation The conditions that cause the LP78073A to reduce charge current through thermal feedback can be approximated by considering the power dissipated in the IC. Nearly all of this power dissipation is generated by the internal MOSFET —this is calculated to be approximately: PD=(VIN-VBAT) • IBAT where PD is the power dissipated, VIN is the input supply voltage, VBAT is the battery voltage and IBAT is the charge current. The approximate ambient temperature at which the thermal feedback begins to protect the IC is: TA=150℃-PDθJA TA=150℃-(VIN-VBAT) • IBAT • θJA PCB Layout Considerations For high frequency switching power supplies, the PCB layout is important step in system application design. In order to let IC achieve good regulation, high efficiency and stability, it is strongly recommended the power components(Inductor, input and output capacitor) should be placed as close as possible to chip. The set races should be wide and short. The feedback pin and then works of feedback and compensation should keep away from the power loops, and be shielded with a ground trace or plane to prevent noise coupling.
LP78073A-01 Jun.-2015 Email: marketing@lowpowersemi.com www.lowpowersemi.com Page 10 of 10 Preliminary Datasheet LP78073A Packaging Information ESOP-8