MCP73861/2
DS21893B-page 16 2005 Microchip Technology Inc.
5.1.6 BATTERY VOLTAGE SENSE (V
BAT3
)
The MCP7386X monitors the battery voltage at the
V
BAT3
pin. This input is tied directly to the positive
terminal of the battery pack.
5.1.7 BATTERY CHARGE CONTROL
OUTPUT (V
BAT1
, V
BAT2
)
The battery charge control output is the drain terminal
of an internal P-channel MOSFET. The MCP7386X
provides constant current and voltage regulation to the
battery pack by controlling this MOSFET in the linear
region. The battery charge control output should be
connected to the positive terminal of the battery pack.
5.2 Digital Circuitry
5.2.1 CHARGE STATUS OUTPUTS
(STAT1,STAT2)
Two status outputs provide information on the state of
charge. The current-limited, open-drain outputs can be
used to illuminate external LEDs. Optionally, a pull-up
resistor can be used on the output for communication
with a host microcontroller. Table 5-1 summarizes the
state of the status outputs during a charge cycle.
The flashing rate (1 Hz) is based off a timer capacitor
(C
TIMER
) of 0.1 µF. The rate will vary based on the
value of the timer capacitor.
During a fault condition, the STAT1 status output will be
off and the STAT2 status output will be on. To recover
from a fault condition, the input voltage must be
removed and then reapplied, or the enable input (EN)
must be de-asserted to a logic-low, then asserted to a
logic-high.
When the voltage on the THERM input is outside the
preset window, the charge cycle will not start, or will be
suspended. The charge cycle is not terminated and
recovery is automatic. The charge cycle will resume or
start once the THERM input is valid and all other
qualification parameters are met. During an invalid
THERM condition, the STAT1 status output will be off
and the STAT2 status output will flash.
5.2.2 V
SET
INPUT
The V
SET
input selects the regulated output voltage of
the MCP7386X. With V
SET
tied to V
SS
, the MCP73861
and MCP73862 regulate to 4.1V and 8.2V, respectively.
With V
SET
tied to V
DD
, the MCP73861 and MCP73862
regulate to 4.2V and 8.4V, respectively.
5.2.3 LOGIC ENABLE (EN)
The logic enable input pin (EN) can be used to
terminate a charge at any time during the charge cycle,
as well as to initiate a charge cycle or initiate a recharge
cycle.
Applying a logic-high input signal to the EN pin, or tying
it to the input source, enables the device. Applying a
logic-low input signal disables the device and termi-
nates a charge cycle. When disabled, the device’s
supply current is reduced to 0.17 µA, typically.
TABLE 5-1: STATUS OUTPUTS
CHARGE
CYCLE STAT1
STAT1 STAT2
Qualification Off Off
Preconditioning On Off
Constant-
Current Fast
Charge
On Off
Constant-
Voltage
On Off
Charge
Complete
Flashing (1 Hz,
50% duty cycle)
Off
Fault Off On
THERM Invalid Off Flashing (1 Hz,
50% duty cycle)
Disabled –
Sleep mode
Off Off
Input Voltage
Disconnected
Off Off
Note: Off state: Open-drain is high-impedance;
On state: Open-drain can sink current,
typically 7 mA;
Flashing: Toggles between off state and
on state.
