FAN5400: USB-Compliant Single Cell Li-Ion Switching Charger with USB-OTG Boost Regulator

The FAN5400 combines a highly integrated switched-mode charger, to minimize single-cell Lithium-ion (Li-ion) charging time from a USB power source, and a boost regulator to power a USB peripheral from the battery.

The charging parameters and operating modes are programmable through an I2C Interface that operates up to 3.4Mbps. The charger and boost regulator circuits switch at 3MHz to minimize the size of external passive components.

The FAN5400 provides battery charging in three phases: conditioning, constant current, and constant voltage.

To ensure USB compliance and minimize charging time, the input current is limited to the value set through the I2C host. Charge termination is determined by a programmable minimum current level. A safety timer with reset control provides a safety backup for the I2C host.

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 enters a high-impedance mode with leakage from the battery to the input prevented. Charge status is reported back to the host through the I2C port. Charge current is reduced when the die temperature reaches 120°C.

The FAN5400 can operate as a boost regulator on command from the system. The boost regulator includes a soft-start that limits inrush current from the battery.

The FAN5400 is available in a 1.96 x 1.87mm, 20-bump, 0.4mm pitch WLCSP package.

Features

• Fully Integrated, High-Efficiency Charger for Single-Cell Li-Ion and Li-Polymer Battery Packs
• Faster Charging than Linear
• Charge Voltage Accuracy:
  • 0.5% at 25°C
  • 1% from 0 to 125°C
• 0.5% at 25°C
• 1% from 0 to 125°C
• ±5% Input Current Regulation Accuracy
• ±5% Charge Current Regulation Accuracy
• 20V Absolute Maximum Input Voltage
• 6V Maximum Input Operating Voltage
• 1.25A Maximum Charge Rate
• Programmable through High-Speed I²C Interface (3.4Mb/s) with Fast Mode Plus Compatibility
  • Input Current
  • Fast-Charge / Termination Current
  • Charger Voltage
  • Termination Enable
• Input Current
• Fast-Charge / Termination Current
• Charger Voltage
• Termination Enable
• 3MHz Synchronous Buck PWM Controller with Wide Duty Cycle Range
• Small Footprint 1µH External Inductor
• Safety Timer with Reset Control
• 1.8V Regulated Output from VBUS for Auxiliary Circuits
• Weak Input Sources Accommodated by Reducing Charging Current to Maintain Minimum VBUS Voltage
• Low Reverse Leakage to Prevent Battery Drain to VBUS
• 5V, 300mA Boost Mode for USB OTG for 2.5 to 4.5V Battery Input

Application Notes