MCP73861 Microchip Technology, Inc., MCP73861 Datasheet - Page 15

• Manufacturer Part Number: MCP73861
• Description: Advanced Single or Dual Cell, Fully Integrated Li-ion / Li-polymer Charge Management Controllersthe MCP7386X Family of Devices Are Highly Advancedlinear Charge Management Controllers For Use in Spacelimited,cost-sensitive Applications. The MCP73861 A
• Manufacturer: Microchip Technology, Inc.

5.0
5.1
5.1.1
The V
The MCP7386X automatically enters a Power-down
mode if the voltage on the V
undervoltage lockout voltage (V
prevents draining the battery pack when the V
supply is not present.
5.1.2
Fast charge current regulation can be scaled by placing
a programming resistor (R
to V
maximum fast charge current of 1.2A, typically. The
minimum fast charge current is 100 mA, set by letting
the PROG input float. The following formula calculates
the value for R
The preconditioning trickle-charge current and the
charge termination current are scaled to approximately
10% and 8% of I
5.1.3
A 2.5V voltage reference is provided to bias an external
thermistor for continuous cell temperature monitoring
and pre-qualification. A ratio metric window compari-
son is performed at threshold levels of V
V
5.1.4
The MCP73861 and MCP73862 continuously monitor
temperature by comparing the voltage between the
THERM input and V
temperature thresholds. A negative or positive temper-
ature coefficient, NTC or PTC, thermistor and an exter-
nal voltage-divider typically develop this voltage. The
temperature sensing circuit has its own reference to
which it performs a ratio metric comparison. Therefore,
it is immune to fluctuations in the supply input (V
The temperature-sensing circuit is removed from the
system when V
discharge of the battery pack.
 2004 Microchip Technology Inc.
where:
THREF
SS
I
R
DD
. Connecting the PROG input to V
REG
PROG
/4.
DETAILED DESCRIPTION
Analog Circuitry
input is the input supply to the MCP7386X.
amps
is the desired fast charge current in
BATTERY MANAGEMENT INPUT
SUPPLY (V
PROG INPUT
CELL TEMPERATURE SENSOR
BIAS (THREF)
CELL TEMPERATURE SENSOR
INPUT (THERM)
R
is in k .
PROG
PROG
DD
REG
is not applied, eliminating additional
:
, respectively.
=
SS
13.2 11 I
----------------------------------------
12 I
DD1
PROG
with the upper and lower
–
, V
REG
DD
) from the PROG input
DD2
–
input falls below the
STOP
REG
1.2
)
). This feature
SS
THREF
allows for a
/2 and
DD
DD
).
Figure 6-1 depicts a typical application circuit with
connection of the THERM input. The resistor values of
R
equations.
For NTC thermistors:
For PTC thermistors:
Applying a voltage equal to V
input disables temperature monitoring.
5.1.5
The TIMER input programs the period of the safety
timers by placing a timing capacitor (C
the TIMER input pin and V
programmed via the timing capacitor.
The preconditioning safety timer period:
The fast charge safety timer period:
And, the elapsed time termination period:
The preconditioning timer starts after qualification and
resets when the charge cycle transitions to the con-
stant current, fast charge phase. The fast charge timer
and the elapsed timer start after the MCP7386X transi-
tions from preconditioning. The fast charge timer resets
when the charge cycle transitions to the constant volt-
age phase. The elapsed timer will expire and terminate
the charge if the sensed current does not diminish
below the termination threshold.
During thermal regulation, the timer is slowed down
proportional to the charge current.
Where:
T1
and R
R
resistance values at the temperature window
of interest.
COLD
t
PRECON
t
TIMER SET INPUT (TIMER)
t
TERM
FAST
T2
R
R
R
R
and
T1
T2
T1
T2
are calculated with the following
=
=
=
=
=
=
=
C
------------------ -
C
------------------ -
R
0.1 F
0.1 F
2 R
----------------------------------------------
2 R
----------------------------------------------
R
2 R
----------------------------------------------
2 R
----------------------------------------------
R
MCP73861/2
C
------------------ -
TIMER
TIMER
0.1 F
HOT
COLD
HOT
R
R
TIMER
COLD
HOT
COLD
COLD
COLD
COLD
SS
–
–
–
3 R
are
. Three safety timers are
1.5Hours
3 R
3.0Hours
–
THREF
R
1.0Hours
R
COLD
HOT
R
R
R
R
COLD
the
HOT
HOT
HOT
HOT
HOT
DS21893A-page 15
/3 to the THERM
TIMER
thermistor
), between