Datasheet

 2011-2013 Microchip Technology Inc. DS20005049C-page 13
MCP73830/L
5.0 DETAILED DESCRIPTION
5.1 Undervoltage Lockout (UVLO)
An Internal Undervoltage Lockout (UVLO) circuit
monitors the input voltage and keeps the charger in
Shutdown mode until the input supply rises above the
UVLO threshold. In the event a battery is present when
the input power is applied, the input supply must rise
approximately 150 mV above the battery voltage
before the MCP73830/L devices become operational.
The UVLO circuit places the device in Shutdown mode
if the input supply falls to approximately 150 mV above
the battery voltage. The UVLO circuit is always active.
Any time the input supply is below the UVLO threshold,
or approximately 150 mV of the voltage at the V
BAT
pin,
the MCP73830/L devices are placed in Shutdown
mode.
5.2 Charge Qualification
When the input power is applied, the input supply must
rise 150 mV above the battery voltage before the
MCP73830/L becomes operational.
The automatic power-down circuit places the device in
Shutdown mode if the input supply falls to within
+50 mV of the battery voltage.
The automatic circuit is always active. Any time the
input supply is within +50 mV of the voltage at the
V
BAT
pin, the MCP73830/L is placed in Shutdown
mode.
For a charge cycle to begin, the automatic power-
down conditions must be met, and the charge enable
input must be above the input high threshold. The
battery voltage should be less than 96.5% of V
REG
.
5.2.1 BATTERY MANAGEMENT INPUT
SUPPLY (V
DD
)
The V
DD
input is the input supply to the MCP73830/L.
The MCP73830/L automatically enters Power-Down
mode if the voltage on the V
DD
input falls to within
+50 mV of the battery voltage. This feature prevents
draining the battery pack when the V
DD
supply is not
present.
5.2.2 BATTERY CHARGE CONTROL
OUTPUT (V
BAT
)
The battery charge control output is the drain terminal
of an internal P-channel MOSFET. The MCP73830/L
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.
5.2.3 BATTERY DETECTION
The MCP73830/L device detects the battery presence
by monitoring the voltage at V
BAT
. The charge flow will
initiate when the voltage on V
BAT
is pulled below the
V
RECHARGE
threshold. Refer to Section 1.0 “Electri-
cal Characteristics” for V
RECHARGE
values. The value
will be the same for non-rechargeable devices.
When V
BAT
>V
REG
+ Hysteresis, the charge will be
suspended or not started, depending on the condition,
to prevent the overcharge that may occur.
5.3 Preconditioning
If the voltage at the V
BAT
pin is less than the precondi-
tioning threshold, the MCP73830/L devices enter
Preconditioning mode. The preconditioning threshold
is factory set. Refer to Section 1.0 “Electrical Charac-
teristics” for preconditioning threshold options.
In this mode, the MCP73830/L devices supply 10% of
the fast charge current (established with the value of
the resistor connected to the PROG pin) to the battery.
When the voltage at the V
BAT
pin rises above the pre-
conditioning threshold, the MCP73830/L device enters
the Constant Current (Fast Charge) mode.
5.3.1 TIMER EXPIRED DURING
PRECONDITIONING MODE
If the internal timer expires before the voltage threshold
is reached for Fast Charge mode, a timer fault is
indicated, and the charge cycle terminates. The
MCP73830/L devices remain in this condition until the
battery is removed, the input power is cycled, or CE
is
toggled. If the battery is removed, the MCP73830/L
devices enter Standby mode, where they remain until a
battery is reinserted.
Note: The MCP73830/L devices also offer
options with no preconditioning.
Note: The typical preconditioning timers for the
MCP73830/L are 60 minutes. The
MCP73830/L also offers options with no
preconditioning timer.