3.2 Lithium Battery Charger (U12)

A 4.2V lithium battery connected to the 2-pin, 2 mm pitch right-angle male battery header can be charged using lithium battery charger (MCP73871-2CC) (U12) from the USB power supply at 100 mA fast charge current.

Battery management circuit automatically handles selection between USB power supply and battery supply. The current is shared between charging the battery (if connected) and the target application section. For more details on the MCP73871 Lithium battery charger, refer to the Stand-Alone System Load Sharing and Li-Ion/Li-Polymer Battery Charge Management Controller Data Sheet (DS20002090).

Table 3-3. Battery Charger Status LED

LED Color

Function

Red (D4)

  • Connected to pin 8 (STAT1)/(LBO bar) (active low signal) of MCP73871
  • STAT1 – Charge status indication. The LBO feature indicates when the battery is running low while operating with battery only. Triggered, if the voltage is <3.1V.
  • The STA1/LBO is also connected to WBZ351PE (PA3) to signal the battery charge status to the WBZ351PE Module.
Blue (D7)

  • Connected to pin 6 Power Good (PG bar (active low signal)) of MCP73871

  • The PG output is low whenever the input to the MCP73871 is above the Undervoltage Lockout (UVLO) threshold and greater than the battery voltage.

Green (D3)

  • Connected to pin 7 (STAT2) of MCP73871
  • Indicates when the battery is fully charged