Datasheet

 2009-2013 Microchip Technology Inc. DS20002183E-page 17
MCP73113/4
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 MCP73113/4 device becomes 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.
At any time, the input supply is below the UVLO
threshold or approximately 150 mV of the voltage at the
V
BAT
pin, the MCP73113/4 device is placed in a
Shutdown mode.
5.2 Overvoltage Protection (OVP)
An internal overvoltage protection (OVP) circuit
monitors the input voltage and keeps the charger in
Shutdown mode when the input supply rises above the
OVP threshold. The hysteresis of OVP is
approximately 150 mV for the MCP73113/4 device.
The MCP73113/4 device is operational between UVLO
and OVP threshold. The OVP circuit is also recognized
as overvoltage lockout (OVLO).
5.3 Charge Qualification
When the input power is applied, the input supply must
rise 150 mV above the battery voltage before the
MCP73113/4 becomes operational.
The automatic power-down circuit places the device in
a Shutdown mode if the input supply falls to within
+50 mV of the battery voltage.
The automatic circuit is always active. At any time the
input supply is within +50 mV of the voltage at the
V
BAT
pin, the MCP73113/4 is placed in a 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.
5.3.1 BATTERY MANAGEMENT INPUT
SUPPLY (V
DD
)
The V
DD
input is the input supply to the MCP73113/4.
The MCP73113/4 automatically enters a 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.
5.3.2 BATTERY CHARGE CONTROL
OUTPUT (V
BAT
)
The battery charge control output is the drain terminal
of an internal P-channel MOSFET. The MCP73113/4
devices provide 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.
5.3.3 BATTERY DETECTION
The MCP73113/4 detects the battery presence by
monitoring the voltage at V
BAT
. The charge flow will ini-
tiate when the voltage on V
BAT
is below the V
RECHARGE
threshold. Refer to Section 1.0 “Electrical Character-
istics” for V
RECHARGE
values. The value will be the
same for the non-rechargeable device.
When V
BAT
> V
REG
+ hysteresis, the charge will be
suspended or not started, depending on the current
charge status, to prevent overcharging.
5.4 Preconditioning
If the voltage at the V
BAT
pin is less than the
preconditioning threshold, the MCP73113/4 device
enters a Preconditioning mode. The preconditioning
threshold is factory set. Refer to Section 1.0
“Electrical Characteristics” for preconditioning
threshold options.
In this mode, the MCP73113/4 device supplies 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 MCP73113/4 device enters
the constant current (Fast Charge) mode.
5.4.1 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
MCP73113/4 device remains in this condition until the
battery is removed or input power is cycled. If the
battery is removed, the MCP73113/4 device enters the
Standby mode where it remains until a battery is
reinserted.
Note: The MCP73113/4 also offer options with
no preconditioning.
Note: The typical preconditioning timer for
MCP73113/4 is 32 minutes. The
MCP73113/4 also offer options with no
preconditioning timer.