MCP73853/55
5.1.6
BATTERY VOLTAGE SENSE (VBAT3)
TABLE 5-2:
STATUS OUTPUT – MCP73855
The MCP73853 monitors the battery voltage at the
VBAT3 pin. This input is tied directly to the positive
terminal of the battery pack.
CHARGE CYCLE STATE
STAT1
Qualification
OFF
ON
Preconditioning
Constant Current Fast Charge
Constant Voltage
Charge Complete
Fault
5.1.7
BATTERY CHARGE CONTROL
OUTPUT (VBAT1, VBAT2
ON
)
ON
The battery charge control output is the drain terminal of
an internal P-channel MOSFET. The MCP7385X
devices provide constant-current and constant-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.
OFF
Flashing (1Hz,
50% duty cycle)
THERM Invalid
Flashing (1Hz,
50% duty cycle)
Disabled - Sleep mode
OFF
OFF
Input Voltage Disconnected
5.2
Digital Circuitry
Note:
OFF state: open-drain is high impedance;
ON state: open-drain can sink current, typ-
ically 7 mA; FLASHING: toggles between
OFF state and ON state.
5.2.1
CHARGE STATUS OUTPUTS
(STAT1,STAT2)
Two status outputs provide information on the state of
charge for the MCP73853. One status output provides
information on the state of charge for the MCP73855.
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 and Table 5-2 summa-
rize the state of the status outputs during a charge
cycle for the MCP73853 and MCP73855, respectively.
The flashing rate (1 Hz) is based off a timer capacitor
(CTIMER) of 0.1 µF. The rate will vary based on the
value of the timer capacitor.
5.2.1.1
MCP73853 Only
STAT2 is on whenever the input voltage is above the
under voltage lockout, the device is enabled, and all
conditions are normal.
During a fault condition, the STAT1 status output will be
off and the STAT2 status output will flash. 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.
TABLE 5-1: STATUS OUTPUTS – MCP73853
CHARGE
STAT1
STAT2
CYCLE STATE
Qualification
OFF
ON
OFF
OFF
OFF
Preconditioning
When the voltage on the THERM input is outside the
preset window, the charge cycle will either not start or
be suspended. However, the charge cycle is not termi-
nated, with recovery beng automatic. The charge cycle
will resume (or start) once the THERM input is valid and
all other qualification parameters are met.
Constant-
current Fast
Charge
ON
Constant-
voltage
ON
OFF
OFF
ON
Charge
Complete
Flashing (1 Hz,
50% duty cycle)
5.2.2
VSET INPUT
Fault
OFF
OFF
The VSET input selects the regulated output voltage of
the MCP7385X devices. With VSET tied to VSS, the
MCP7385X devices regulate to 4.1V. With VSET tied to
THERM Invalid
Flashing (1 Hz,
50% duty cycle)
VDD, the MCP7385X devices regulate to 4.2V.
Disabled -
Sleep mode
OFF
OFF
OFF
5.2.3 LOGIC ENABLE (EN)
Input Voltage
Disconnected
OFF
The logic enable input pin (EN) can be used to termi-
nate a charge anytime during the charge cycle, initiate
a charge cycle or initiate a recharge cycle.
Note:
OFF state: open-drain is high-impedance;
ON state: open-drain can sink current,
typically 7 mA; FLASHING: toggles
between OFF and ON states.
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 0.28 µA, typically.
DS21915A-page 14
2004 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
