Datasheet

 2009-2013 Microchip Technology Inc. DS22191E-page 13
MCP73123/223
The charge current is established using a single
resistor from PROG to V
SS
. The program resistor and
the charge current are calculated using
Equation 5-1
and Equation 5-2.
EQUATION 5-1:
EQUATION 5-2:
Table 5-1 provides commonly seen E96 (1%) and E24
(5%) resistors for various charge current to reduce
design time.
TABLE 5-1: RESISTOR LOOKUP TABLE
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.
5.5.1 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 MCP73123/223 device
remains in this condition until the battery is removed. If
the battery is removed or input power is cycled, the
MCP73123/223 device enters the Standby mode,
where it remains until a battery is reinserted.
5.6 Constant Voltage Mode
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 3.6V for
a single cell, with a tolerance of ±0.5%; or 7.2V for dual
cells, with a tolerance of ±0.6%.
5.7 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 5%,
7.5%, 10% or 20% of fast charge current
or 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
timer period is factory set and can be disabled. Refer to
Section 1.0, "Electrical Characteristics", for timer
period options.
5.8 Automatic Recharge
The MCP73123/223 device continuously monitors the
voltage at the V
BAT
pin in 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 MCP73123/223 device with no recharge option,
the MCP73123/223 will go into Standby mode when the
termination condition is met. The charge will not restart
until at least one of the following conditions have been
met:
• The battery is removed from the system and
inserted again
•V
DD
is removed and plugged in again
• R
PROG
is disconnected (or high impedance) and
reconnected
Charge
Current (mA)
Recommended
E96 Resistor ()
Recommended
E24 Resistor ()
130 10k 10k
150 8.45k 8.20k
200 6.20k 6.20k
250 4.99k 5.10k
300 4.02k 3.90k
350 3.40k 3.30k
400 3.00k 3.00k
450 2.61k 2.70k
500 2.32k 2.37k
550 2.10k 2.20k
600 1.91k 2.00k
650 1.78k 1.80k
700 1.62k 1.60k
750 1.50k 1.50k
800 1.40k 1.50k
850 1.33k 1.30k
900 1.24k 1.20k
950 1.18k 1.20k
1000 1.10k 1.10k
1100 1.00k 1.00k
I
REG
1104 R
0.93–
 =
Where:
R
PROG
=kilo-ohms (k)
I
REG
= milliampere (mA)
R
PROG
10
I
REG
1104log 0.93–  
=
Where:
R
PROG
=kilo-ohms (k)
I
REG
= milliampere (mA)
Note: The MCP73123/223 also offer options
with no automatic recharge.