Datasheet

© 2009 Microchip Technology Inc. DS22190B-page 17
MCP73213
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 MCP73213 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 MCP73213 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
typical 13V, OVP threshold. The hysteresis of OVP is
approximately 150 mV for the MCP73213 device.
The MCP73213 device is operational between UVLO
and OVP threshold. The OVP circuit is also recognized
as overvoltage lock out (OVLO).
5.3 Charge Qualification
When the input power is applied, the input supply must
rise 150 mV above the battery voltage before the
MCP73213 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 MCP73213 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 MCP73213.
The MCP73213 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 MCP73213
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.
5.3.3 BATTERY DETECTION
The MCP73213 detects the battery presence with
charging of the output capacitor. The charge flow will
initiate when the voltage on V
BAT
is pulled below the
V
RECHARGE
threshold. Refer to Section 1.0
“Electrical Characteristics” for V
RECHARGE
values.
The value will be the same for non-rechargeable
device.
When V
BAT
>V
REG
+ Hysteresis, the charge will be
suspended or not start, depending on the condition to
prevent over charge that may occur.
5.4 Preconditioning
If the voltage at the V
BAT
pin is less than the
preconditioning threshold, the MCP73213 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 MCP73213 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
preconditioning threshold, the MCP73213 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
MCP73213 device remains in this condition until the
battery is removed or input power is cycled. If the
battery is removed, the MCP73213 device enters the
Stand-by mode where it remains until a battery is
reinserted.
Note: The MCP73213 device also offers options
with no preconditioning.
Note: The typical preconditioning timer for
MCP73213 is 32 minutes. The MCP73213
also offers options with no preconditioning
timer.