MCP73831/2
5.2
Digital Circuitry
5.0
DETAILED DESCRIPTION
5.2.1
STATUS INDICATOR (STAT)
5.1
Analog Circuitry
The charge status output of the MCP73831 has three
different states: High (H), Low (L), and High-Imped-
ance (Hi-Z). The charge status output of the
MCP73832 is open-drain, and, as such, has two differ-
ent states: Low (L), and High-Impedance (Hi-Z). The
charge charge status output can be used to illuminate
1, 2, or tri-color LEDs. Optionally, the charge status
output can be used as an interface to a host
microcontroller.
5.1.1
BATTERY MANAGEMENT INPUT
SUPPLY (VDD
)
The VDD input is the input supply to the MCP73831/2.
The MCP73831/2 automatically enter a Power-Down
mode if the voltage on the VDD input falls below the
UVLO voltage (VSTOP). This feature prevents draining
the battery pack when the VDD supply is not present.
5.1.2
CURRENT REGULATION SET
(PROG)
Table 5-1 summarize the state of the status output
during a charge cycle..
Fast charge current regulation can be scaled by plac-
ing a programming resistor (RPROG) from the PROG
input to VSS. The program resistor and the charge
current are calculated using the following equation:
TABLE 5-1:
STATUS OUTPUT
STAT1
MCP73831 MCP73832
Charge Cycle State
Shutdown
Hi-Z
Hi-Z
L
Hi-Z
Hi-Z
L
1000V
RPROG
----------------
=
IREG
No Battery Present
Preconditioning
Where:
Constant-Current Fast
Charge
L
L
RPROG
IREG
=
=
kOhms
milliampere
Constant Voltage
L
L
Charge Complete –
Standby
H
Hi-Z
The preconditioning trickle charge current and the
charge termination current are ratiometric to the fast
charge current based on the selected device options.
5.2.2
DEVICE DISABLE (PROG)
The current regulation set input pin (PROG) can be
used to terminate a charge at any time during the
charge cycle, as well as to initiate a charge cycle or
initiate a recharge cycle.
5.1.3
BATTERY CHARGE CONTROL
OUTPUT (VBAT
)
The battery charge control output is the drain terminal
of an internal P-channel MOSFET. The MCP73831/2
provide constant current and voltage regulation to the
battery pack by controlling this MOSFET in the linear
region. The battery charge control output should be
connected to the positive terminal of the battery pack.
Placing a programming resistor from the PROG input
to VSS enables the device. Allowing the PROG input to
float or by applying a logic-high input signal, disables
the device and terminates a charge cycle. When
disabled, the device’s supply current is reduced to
25 μA, typically.
DS21984B-page 12
© 2006 Microchip Technology Inc.