Microchip Technology MCP7383XRD-PPM Data Sheet

DS22005B-page 14

© 2009 Microchip Technology Inc.

An internal under voltage lockout (UVLO) circuit
monitors the input voltage and keeps the charger in
shutdown mode until the input supply rises above the
UVLO threshold. The UVLO circuitry has a built-in
hysteresis of 100 mV.
In the event a battery is present when the input power
is applied, the input supply must rise +150 mV above
the battery voltage before the MCP73833/4 becomes
operational.
The UVLO circuit places the device in shutdown mode
if the input supply falls to within +50 mV of the battery
voltage. 
The UVLO circuit is always active. At any time the input
supply is below the UVLO threshold or within +50 mV
of the voltage at the V

BAT

 pin, the MCP73833/4 is

placed in a shutdown mode.
During any UVLO condition, the battery reverse
discharge current shall be less than 2 µA.

For a charge cycle to begin, all UVLO conditions must
be met and a battery or output load must be present.
A charge current programming resistor must be
connected from PROG to V

SS

. If the PROG pin is open

or floating, the MCP73833/4 is disabled and the battery
reverse discharge current is less than 2 µA. In this
manner, the PROG pin acts as a charge enable and
can be used as a manual shutdown.
If the input supply voltage is above the UVLO
threshold, but below V

REG

(Typical)+0.3V, the

MCP73833/4 will pulse the STAT1 and PG outputs as
the device determines if a battery is present.

If the voltage at the V

BAT

 pin is less than the

preconditioning threshold, the MCP73833/4 enters a
preconditioning or trickle charge mode. The
preconditioning threshold is factory set. Refer to
Section 1.0 “Electrical Characteristics” for
preconditioning threshold options.
In this mode, the MCP73833/4 supplies a percentage
of the charge current (established with the value of the
resistor connected to the PROG pin) to the battery. The
percentage or ratio of the current is factory set. Refer to
Section 1.0 “Electrical Characteristics” for
preconditioning current options.
When the voltage at the V

BAT

 pin rises above the pre-

conditioning threshold, the MCP73833/4 enters the
constant current or fast charge mode.

During the constant current mode, the programmed
charge current is supplied to the battery or load. The
charge current is established using a single resistor
from PROG to V

SS

. The program resistor and the

charge current are calculated using 

Constant current mode is maintained until the voltage
at the V

BAT

 pin reaches the regulation voltage, V

REG

.

When constant current mode is invoked, the internal
timer is reset.

4.4.1

TIMER EXPIRED DURING 
CONSTANT CURRENT - FAST 
CHARGE MODE

If the internal timer expires before the recharge voltage
threshold is reached, a timer fault is indicated and the
charge cycle terminates. The MCP73833/4 remains in
this condition until the battery is removed, the input
power is removed, or the PROG pin is opened. If the
battery is removed or the PROG pin is opened, the
MCP73833/4 enters the Standby mode where it
remains until a battery is reinserted or the PROG pin is
reconnected. If the input power is removed, the
MCP73833/4 is in Shutdown. When the input power is
reapplied, a normal start-up sequence ensues.

When the voltage at the V

BAT

 pin reaches the

regulation voltage, V

REG

, constant voltage regulation

begins. The regulation voltage is factory set to 4.20V,
4.35V, 4.40V, or 4.50V with a tolerance of ± 0.75%.

The charge cycle is terminated when, during constant
voltage mode, the average charge current diminishes
below a percentage of the programmed charge current
(established with the value of the resistor connected to
the PROG pin) or the internal timer has expired. A 1 ms
filter time on the termination comparator ensures that
transient load conditions do not result in premature
charge cycle termination. The percentage or ratio of the
current is factory set. The timer period is factory set
and can be disabled. Refer to Section 1.0 “Electrical
Characteristics” for charge termination current ratio
and timer period options. 
The charge current is latched off and the MCP73833/4
enters a charge complete mode.

Where:

R

PROG

= kilo-ohms

I

REG

= milliampere