Design a Li-Ion Battery Charger and Load Sharing System

There are items that need to be considered with load sharing for battery management product. Load cannot be directly connected to the VBAT pins of the Li-Ion battery chargers for the following reasons:

  1. The charge may never end. Most Li-Ion battery chargers are based on Constant Current and Constant Voltage (CC-CV) modes.
  2. The total system current is limited by the charge current because the charger will deliver total system and battery charging current through the output pin. Please refer to AN1149 for more information on load sharing implementation.

The other solution is to use a battery charger that has a load sharing capability. Please check the MCP73871 device. You can see that it has a VBAT pin for the battery and OUT pin for the load. It internally implements what is mentioned in the AN1149.

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