MAXREFDES1214: Portable 1.5A USB charger with Micro-USB input and USB Standard-A output

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

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