MCP73853IMF MICROCHIP [Microchip Technology], MCP73853IMF Datasheet - Page 11

• Manufacturer Part Number: MCP73853IMF
• Description: USB Compatible Li-Ion/Li-Polymer Charge Management Controllers
• Manufacturer: MICROCHIP [Microchip Technology]

4.0
The MCP7385X devices are highly advanced linear
charge management controllers. Refer to the functional
block diagram. Figure 4-2 depicts the operational flow
algorithm from charge initiation to completion and
automatic recharge.
4.1
Upon insertion of a battery, or application of an external
supply, the MCP7385X devices automatically perform a
series of safety checks to qualify the charge. The input
source voltage must be above the Undervoltage Lock-
out (UVLO) threshold, the enable pin must be above the
logic high level, and the cell temperature monitor must
be within the upper and lower thresholds (MCP73853
only). The qualification parameters are continuously
monitored, with any deviation beyond the limits automat-
ically suspending, or terminating, the charge cycle. The
input voltage must deviate below the UVLO stop
threshold for at least one clock period to be considered
valid.
Once the qualification parameters have been met, the
MCP7385X devices initiate a charge cycle. The charge
status output is pulled low throughout the charge cycle
(see Tables 5-1 and 5-2 for charge status outputs). If
the battery voltage is below the preconditioning thresh-
old (V
battery with a trickle charge. The preconditioning
current is set to approximately 10% of the fast charge
regulation current. The preconditioning trickle charge
safely replenishes deeply depleted cells and minimizes
heat dissipation during the initial charge cycle. If the
battery voltage has not exceeded the preconditioning
threshold before the preconditioning timer has expired,
a fault is indicated and the charge cycle is terminated.
4.2
Preconditioning ends and fast charging begins when
the battery voltage exceeds the preconditioning thresh-
old. Fast charge regulates to a constant current (I
which is set via an external resistor connected to the
PROG pin. Fast charge continues until either the
battery voltage reaches the regulation voltage (V
or the fast charge timer expires; in which case, a fault
is indicated and the charge cycle is terminated.
4.3
When the battery voltage reaches the regulation volt-
age (V
MCP7385X devices monitor the battery voltage at the
V
nal of the battery. The MCP7385X devices select the
voltage regulation value based on the state of V
 2004 Microchip Technology Inc.
BAT
pin. This input is tied directly to the positive termi-
PTH
REG
DEVICE OVERVIEW
Charge Qualification and
Preconditioning
Constant Current Regulation –
Fast Charge
Constant Voltage Regulation
), the MCP7385X devices precondition the
), constant voltage regulation begins. The
REG
REG
SET
),
)
.
With V
to 4.1V. With V
regulate to 4.2V.
4.4
The MCP7385X devices monitor the charging current
during the Constant-voltage Regulation mode. The
charge cycle is considered complete when either the
charge current has diminished below approximately
7% of the regulation current (I
has expired.
The MCP7385X devices automatically begin a new
charge cycle when the battery voltage falls below the
recharge threshold (V
tion parameters are met.
4.5
The MCP7385X devices limit the charge current based
on the die temperature. Thermal regulation optimizes
the charge cycle time while maintaining device reliabil-
ity. If thermal regulation is entered, the timer is automat-
ically slowed down to ensure that a charge cycle will
not terminate prematurely. Figure 4-1 depicts the
thermal regulation.
FIGURE 4-1:
Current vs. Junction Temperature.
4.6
The MCP7385X devices suspend charge if the die
temperature exceeds 155°C. Charging will resume
when the die temperature has cooled by approximately
10°C. The thermal shutdown is a secondary safety
feature in the event that there is a failure within the
thermal regulation circuitry.
450
400
350
300
250
200
150
100
SET
50
0
0
Charge Cycle Completion and
Automatic Recharge
Thermal Regulation
Thermal Shutdown
tied to V
20
SET
SS
tied to V
MCP73853/55
40
Junction Temperature (C)
, the MCP7385X devices regulate
RTH
Typical Maximum Charge
Minimum
), assuming all the qualifica-
60
DD
REG
, the MCP7385X devices
80
), or the elapsed timer
DS21915A-page 11
100
Maximum
120
140