feature

Fully integrated single-cell high-efficiency charger Li-Ion and Li-polymer battery packs charge faster than linear charging Voltage Accuracy: ±0.5% at 25°C ±1% at 0 to 125 °C Input Current Regulation Accuracy ±5% Charge current regulation accuracy is ±5% 20 V absolute maximum input voltage 6 V Maximum input operating voltage 1.45 A Charge/Termination Current – Charger Voltage – Terminal Enable 3 MHz Wide Synchronous Buck PWM Controller Duty Cycle Range Small Size 1 μh External Inductor Safety Timer with Reset Control 1.8V Regulation for Auxiliary Circuits from VBU Output Output Dynamic Input Voltage Control Low Reverse Leakage Prevents Battery Drain to VBU5V, 500mA USB OTG Boost Mode, 3.0V to 4.5V Battery Input Provides 1.96 x 1.87mm, 20-Bump, 0.4mm Pitch WLCSP Bag

application

Cell Phones, Smartphones, Pocket PCs Tablets, Portable Media Players Gaming Devices, Digital Cameras

describe

The FAN54015 incorporates a highly integrated switch-mode charger that minimizes single-cell Li-Ion (Li-Ion) charging from a USB power supply and boost regulator to powering USB peripherals from the battery. The charging parameters and working mode are programmable through the i2 C interface, and the operation can reach 3.4 Mbps. The charger and boost regulator circuits operate at 3 MHz, minimizing the size of external passive components. The FAN54015 provides three-phase battery charging: regulated, constant current and constant voltage. To ensure USB compatibility and minimize charging time, the input current limit can be changed via the I2C host processor. Charge is terminated by a programmable minimum current level. Safety timer reset control provides a safety backup C host for i2. The charging status is reported to the host C port via the i2. The integrated circuit (IC) automatically restarts the charge cycle when the battery falls below an internal threshold. If the input source is removed, the IC goes into high impedance mode, preventing battery leakage to the input. When the die temperature is reached, the charging current is reduced by 120°C, protecting the device and PCB from damage. The fan 54015 can work as a boost regulator on command from the system. The boost regulator includes soft-start, limits inrush current from the battery and uses the same external components used to charge the battery

Circuit Description/Overview

When charging a battery with a limited current input source, such as USB, the high efficiency of a switching charger over a wide range of output voltages minimizes charging time. The FAN54015 incorporates a highly integrated synchronous buck regulator charged with a synchronous boost regulator, which can supply 5V to mobile USB (OTG) peripherals. The regulator uses a synchronous rectifier charger and boost regulator to maintain high efficiency over a wide range of battery voltages and states of charge. Fan 54015 has three working modes: 1. Charging mode: charging single-cell Li-ion or Li-polymer battery. 2. Boost Mode: Provide 5 V power supply for USB-OTG with synchronous rectification boost regulator battery as input. 3. High Impedance Mode: During this process, both the boost and charging circuits are disconnected. From VBU to battery or from battery in this mode, VBUS is blocked. This mode consumes very little current from VBU or battery. Note: Default settings are shown in bold font. Charging Mode In charging mode, FAN54015 adopts four regulation loops: 1. Input current: limit from VBUS. This current is sensed internally and can be programmed via the i2C interface. 2. Charging current: limit the maximum charging current. This current is induced by an external resistor. 3. Charging voltage: The regulator is limited to exceeding this voltage. As the internal battery voltage rises, the battery's internal impedance and induction work in conjunction with charging voltage regulation to reduce the amount of current flowing into the battery. When the voltage passes, the battery is fully charged and the rsense is below the iterm threshold. 4. Temperature: If the junction temperature of the IC reaches 120°C, reduce the charging current until the IC temperature stabilizes at 120°C. 5. Additional loops limit the amount of droop on vbus to a programmable voltage (VSP) to accommodate "special chargers that limit current to lower currents than possible available from "normal" USB wall chargers. Batteries Charge Profile If the battery voltage is below VShort, the battery is precharged for a linear current source until VBAT reaches Vshort. Pulse width modulation then starts the charging circuit and charges the battery Constant current is used if there is enough input power. Limits the current The slew rate to prevent overshooting FAN54015 is designed to current limit the input source of vbus. During the current regulation phase the charge current or program charge current limits the amount of current available for battery charging to power the system. The effect of iInLim on iCharge

Assuming that VOREG is programmed to the cell's charging "float" voltage, the current drawn by the cell with the PWM regulator limiting its output (sensed at VBAT) until VOREG drops, and the charger enters the voltage charge regulation phase. When the current drops to the programmed iterm value, the charge cycle is complete. This can be done by resetting the TE bit (reg1[3]). Charger output or "float" voltage programmable with OREG bits from 3.5 V to 4.44 V in 2 0mV increments pwm controller IC in charge mode uses current mode pwm controller to regulate output voltage and battery charge current . The synchronous rectifier (q2) has a current limit when the negative peak current exceeds 140ma. This prevents current from flowing out of the battery. When the safety timer charging starts, the IC starts a 15-minute timer (T15min). When it times out, charging is terminated. A write sent via i2 to any register C stops and resets the T15min timer, then starts the 32 second timer (T32s). Setting the tmr_rst bit (reg0[7]) resets the t32s timer. If the T32S timer times out; charging is terminated, the registers are set to their default values, and then continue to charge using the default values when the T15min timer was running. Normal charging is run by the host through T32S timer control to ensure the host is active. Running to the T15min timer for charging, if the 15min timer expires, the IC will turn off the charger, set the bits, and indicate the timer fault (110) and turn on the fault bits (reg0[2:0]). This sequence prevents overcharging if the host fails to reset the T32S timer. The vbus-por/incompatible charger rejects the IC applying a 100 load from VBUS to GND when the IC detects that VBU rises above VIN (min) 1 (4.4 V). Until the VBUS por is cleared (power on reset) and charging begins, the VBU must remain above VIN (min) 1 and below VIN (min) 1 TVBUS is active (30ms) before the IC starts charging. This VBUS verification sequence always occurs before charging or restarting (eg after VBUS ovp failure or VRCH charging start). TVBUS effectively ensures that unfiltered 50/60 Hz chargers and other non-compliant chargers will be rejected. The USB friendly boot sequence is in vbus por, when the battery voltage is higher than the weak voltage battery threshold (VLOWV), the IC is set according to the IT2C register. if vbat