MCP73827 Microchip Technology, Inc., MCP73827 Datasheet - Page 10

• Manufacturer Part Number: MCP73827
• Description: The MCP73827 is a Battery Charger Controller For Single Cell Li-ion Batteries
• Manufacturer: Microchip Technology, Inc.

MCP73827
5.0
Refer to the typical application circuit, Figure 6-1.
5.1
5.1.1
The I
tional to the battery charging current. It is an amplified
version of the sense resistor voltage drop that the cur-
rent loop uses to control the external P-channel pass
transistor. This voltage signal can be applied to the
input of an A/D Converter and used by a host microcon-
troller to display information about the state of the bat-
tery or charge current profile.
5.1.2
The MCP73827 monitors the cell voltage at the V
pin. This input is tied directly to the positive terminal of
the battery. The MCP73827 is offered in two fixed-volt-
age versions for single cells with either coke or graphite
anodes:
(MCP73827-4.2).
5.1.3
The MCP73827 controls the gate drive to an external
P-channel MOSFET, Q1. The P-channel MOSFET is
controlled in the linear region, regulating current and
voltage supplied to the cell. The drive output is auto-
matically turned off when the input supply falls below
the voltage sensed on the V
5.1.4
Fast charge current regulation is maintained by the
voltage drop developed across an external sense resis-
tor, R
ing formula calculates the value for R
Where:
5.1.5
The V
MCP73827 automatically enters a power-down mode if
the voltage on the V
the V
pack when the V
DS21704A-page 10
V
I
amps. The preconditioning current is scaled to
approximately 43% of I
MON
OUT
BAT
SENSE
IN
CS
input is the input supply to the MCP73827. The
DETAILED DESCRIPTION
Analog Circuitry
CHARGE CURRENT MONITOR (I
CELL VOLTAGE MONITORED INPUT
(V
GATE DRIVE OUTPUT (V
CURRENT SENSE INPUT (V
SUPPLY VOLTAGE (V
is the current limit threshold
pin. This feature prevents draining the battery
pin provides an output voltage that is propor-
is the desired peak fast charge current in
BAT
, applied to the V
4.1V
)
IN
supply is not present.
R
IN
SENSE
(MCP73827-4.1)
input falls below the voltage on
PEAK
=
BAT
SNS
----------- -
I
V
O UT
CS
input.
IN
.
input pin. The follow-
)
DRV
SENSE
SNS
)
and
)
:
MON
)
4.2V
BAT
5.2
5.2.1
The shutdown input pin, SHDN, can be used to termi-
nate a charge anytime during the charge cycle, initiate
a charge cycle, or initiate a recharge cycle.
Applying a logic High input signal to the SHDN pin, or
tying it to the input source, enables the device. Apply-
ing a logic Low input signal disables the device and ter-
minates a charge cycle. In shutdown mode, the
device’s supply current is reduced to 0.5 µA, typically.
5.2.2
A charge status output, MODE, provides information on
the state of charge. The open drain output can be used
to illuminate an external LED. Optionally, a pull-up
resistor can be used on the output for communication
with a microcontroller. Table 5-1 summarizes the state
of the charge status output during a charge cycle.
TABLE 5-1:
Qualification
Preconditioning
Controlled Current Fast Charge
Constant Voltage
Disabled - Sleep mode
Battery Disconnected
Charge Cycle State
Digital Circuitry
SHUTDOWN INPUT (SHDN)
CHARGE STATUS OUTPUT (MODE)
Charge Status Output.
2002 Microchip Technology Inc.
Mode
OFF
OFF
OFF
OFF
ON
ON