System Board 6880

MAXREFDES1214: Portable 1.5A USB Charger with Micro-USB Input and USB Standard-A Output

 Download Full Reference Design

Input Type VIN (MIN)
Isolated/Non-Isolated Topology
DC 4.2  1.5 Single 5.0 7.5  Non-Isolated  Buck-Boost

The MAXREFDES1214 is a portable USB charger that uses a lithium-ion (Li+) battery to charge a USB device from a USB Standard-A connector. The battery can be charged through Micro-USB. The MAXREFDES1214 is compliant with USB Battery Charger (BC) revision 1.2 on both USB ports. It has dynamic charger detection to automatically set the maximum charge current allowed to the battery based on the source’s capability. It also features a USB adapter emulator that supports Apple® 1A charging in addition to devices that are compliant with USB BC 1.2. For added flexibility, an I2C bus provides fault monitoring and shutdown capability for the buckboost regulator.

Key Features

  • Battery Charger Input Current up to 1A
  • USB Standard-A Output Current up to 1.5A
  • 4400mAh Li+ Battery
  • Thermal and Overcurrent Protection on the USB Standard-A Output
  • I2C Headers for Flexible Logic Levels from 1.8V to 5.0V
  • Orange LED to Indicate if the Battery Is Charging
  • No External Reverse Blocking Diode Required Between Battery and Charger
MAXREFDES1214 Board Enlarge+

This board is not available for purchase.

Designed, Built, Tested

This document describes the hardware shown above. It provides the design procedure for the MAXREFDES1214, including the USB detection and enumeration circuitry, Li+ battery charger, buck-boost converter, and logic-level translation. The design has been built and tested, details of which follow later in this document.

Design Resources


High-Efficiency Buck-Boost Regulator with 5A Switches

  • Buck and Boost Operation Including Seamless Transition between Buck and Boost Modes
  • I2C Serial Interface Allows Dynamic VOUT Adjustment and Provides Design Flexibility
  • 97.5% Peak Efficiency

USB Charger Adapter Emulators

  • Optimized for Charging Adapters
  • Faster Charging
  • Improved Charger Interoperability

USB Charger Detectors

  • High Level of Integration
  • Save Power in Portable Applications
  • Space Saving

High-Speed, Open-Drain Capable Logic-Level Translator

  • Meets Industry Standards
  • Allows Greater Design Flexibility
  • Ultra-Low Power Consumption

High PSRR, Low-Dropout, 150mA Linear Regulators

  • Space-Saving SC70 Package
  • 65dB PSRR at 10kHz
  • 120mV Dropout at 120mA Load

1A Linear Li+ Battery Chargers with Integrated Pass FET and Thermal Regulation in 2mm x 2mm TDFN

  • Stand-Alone Linear 1-Cell Li+ Battery Charger
  • No External FET, Reverse Blocking Diode, or Current-Sense Resistor Required
  • Programmable Fast-Charge Current (1A max)