MCP73871 - Stand-Alone System Load Sharing and Li-Ion/Li-Polymer Battery Charge Management Controller

When is the low battery output (LBO) feature enabled on the MCP73871?

When the system is running on the Li-Ion battery.

At what voltage is the low battery output (LBO) triggered?

About 3.1 V. Refer to the "DC Characteristics" section of the device datasheet.

For the LBO feature to work, does the Li-Ion battery have to be above the LBO voltage?

Refer to the device datasheet, then look for the Undervoltage Lockout (UVLO) stop threshold. The UVLO stops the device when Vin = VREG + 70 mV (typical) = 4.27 V.

Are the Voltage Proportional Current Control (VPCC) and LBO features compatible?

They are compatible. The VPCC function reduces the battery charging current, so Vin is greater than the UVLO stop threshold. Vin supplies the load and the battery that is still in the charging process, but the charging current is reduced. As long as the battery is in the charging process, the LBO features are not used.

Is the MCP73871 output voltage regulated or equal to the input voltage?

The output voltage is not regulated and it is close to the input voltage: Vout = Vin - 2 Ω * Iout.

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