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.


  • 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
  • ±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
  • 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
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Product Product &
Eco Status
Unit Price/
1K Order
Packing Method Convention Package Marking
FAN5400UCX Full Production
Green as of Jan 2010
 China RoHS

WL-CSP 20L  -  Details
0.625 x 0 x 0mm,  TAPE REEL

PDF WL-CSP 20L  Drawing
Last Update: Nov 2015 PDF WLCSP UC020AA, Packing Drawing
Last Update: Jan 2016
Line 1AH&K

Line 2&. (Pin One)
&2 (2-Digit Date Code)
&Z (Plant Code)

FIT [Calculate] 1.06 @55°C
MTBF 9.47E8

ESD (HBM) 2000V

Moisture Sensitivity Level (MSL) 1

Max Reflow Temp 260

PDF China RoHS

If there is no sample button displayed at the top of the page, please contact one of the Fairchild distributors or your local sales office to obtain samples.
* Click here for further top mark packaging information for FAN5400

  • TBA
Application Note Description
AN-9720 PDFPower Path Implementation Tradeoffs, Featuring the FAN5400 Family of PWM Battery Chargers
Last Update : 28-Jun-2014
AN-9721 PDFLi-Ion Battery Charging Basics, Featuring the FAN5400 / FAN5420 Family of PWM Battery Chargers
Last Update : 03-Mar-2011

Distributor Inventory

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Fairchild Product Availability (Projected Cumulative Factory Inventory)

Product Product Availability Date Total Projected Inventory
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(0.3 - 1.4)
T use (°C)
T Stress (°C)
Kt (eV/K)
Device Hours
@ T Stress
FIT @ T use
use (hours)
FAN5400UCX 0.7 0.6 55 150 8.62E-05 7389294.43 1 4.04 259.24 1.06
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