Datasheet

MCP73871
DS20002090C-page 26 2008-2013 Microchip Technology Inc.
5.2.2 AC-DC ADAPTER AND USB PORT
POWER SOURCE REGULATION
SELECT (SEL)
With the SEL input Low, the MCP73871 device is
designed to provide system power and Li-Ion battery
charging from a USB input while adhering to the current
limits governed by the USB specification. The host
microcontroller has the option to select either
a 100 mA (L) or a 500 mA (H) current limit based on
the PROG2 input. With the SEL input High, the
MCP73871 device limits the input current to 1.8A. The
programmed charge current is established using a
single resistor from PROG1 to V
SS
when driving SEL
High.
5.2.3 USB PORT CURRENT
REGULATION SELECT (PROG2)
Driving the PROG2 input to a logic Low selects the low
USB port source current setting (maximum 100 mA).
Driving the PROG2 input to a logic High selects the
high USB port source current setting (maximum
500 mA).
5.2.4 POWER-GOOD (PG)
The power-good (PG) option is a pseudo open-drain
output. The
PG output can sink current, but not source
current. The
PG output must not be pulled up higher
than V
IN
because there is a diode path back to V
IN
. The
PG output is low whenever the input to the MCP73871
device is above the UVLO threshold and greater than
the battery voltage. The
PG output can be used as an
indication to the system that an input source other than
the battery is supplying power.
5.2.5 TIMER ENABLE (TE) OPTION
The timer enable (TE) input option is used to enable or
disable the internal timer. A low signal on this pin
enables the internal timer and a high signal disables
the internal timer. The
TE input can be used to disable
the timer when the charger is supplying current to
charge the battery and power the system load. The
TE
input is compatible with 1.8V logic.