Datasheet

MCP73830/L
DS20005049C-page 14  2011-2013 Microchip Technology Inc.
5.4 Constant Current Mode – Fast
Charge
During Constant Current mode, the programmed
charge current is supplied to the battery or load.
The charge current is established using a single resis-
tor from PROG to V
SS
. The program resistor and the
charge current are calculated using the following
equation:
EQUATION 5-1: MCP73830L
EQUATION 5-2: MCP73830
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.
5.4.1 TIMER EXPIRED DURING
CONSTANT CURRENT – FAST
CHARGE MODE
If the internal 4-hour timer expires before the recharge
voltage threshold is reached, a timer fault is indicated
and the charge cycle terminates. The MCP73830/L
devices remain in this condition until the battery is
reinserted, or the input power or CE
is cycled.
5.5 Constant Voltage Mode
When voltage at the V
BAT
pin reaches the regulation
voltage, V
REG
, the constant voltage regulation begins.
The regulation voltage is factory set to 4.2V, with a
tolerance of ±0.75%.
5.6 Charge Termination
The charge cycle is terminated when, during Constant
Voltage mode, the average charge current diminishes
below a threshold established with the value of 7.5%,
10% of fast charge current,
or the internal timer has
expired. A 1 ms filter time on the termination compara-
tor ensures that transient load conditions do not result
in premature charge cycle termination. The timer
period is factory set and no timer option is available.
Refer to Section 1.0 “Electrical Characteristics” for
timer period options.
5.7 Automatic Recharge
MCP73830/L devices with automatic recharge options
continuously monitor the voltage at the V
BAT
pin during
the Charge Complete mode. If the voltage drops below
the recharge threshold, another charge cycle begins,
and current is once again supplied to the battery or
load. The recharge threshold is factory set. Refer to
Section 1.0 “Electrical Characteristics” for recharge
threshold options.
For the MCP73830/L with no recharge option, the
devices will go into Standby mode when a termination
condition is met. The charge will not restart until one of
the following conditions is met:
• Battery is removed from the system and inserted
again.
•V
DD
is removed and plugged in again
•CE
is cycled.
5.8 Thermal Regulation
The MCP73830/L should limit the charge currents
based on the die temperature. The thermal regulation
optimizes the charge cycle time while maintaining
device reliability. Figure 5-1 depicts the thermal
regulation for the MCP73830/L devices. Refer to
Section 1.0 “Electrical Characteristics” for thermal
package resistances, and Section 6.1.1.2 “Thermal
Considerations” for calculating power dissipation.
.
FIGURE 5-1: Thermal Regulation.
I
REG
200
R
PROG
--------------------=
Where:
R
PROG
=kilo-ohms (k)
I
REG
= milliampere (mA)
I
REG
1000
R
PROG
--------------------=
Where:
R
PROG
=kilo-ohms (k)
I
REG
= milliampere (mA)
Note: The MCP73830/L also offer options with
no automatic recharge.
0
50
100
150
200
250
300
0306090120150
Junction Temperature (C)
Maximum Charge Current (mA)
Mimimum
Maximum