MCP73831/2
4.0
DEVICE OVERVIEW
The MCP73831/2 are highly advanced linear charge
management controllers. Figure 4-1 depicts the
operational flow algorithm from charge initiation to
completion and automatic recharge.
The UVLO circuit places the device in Shutdown mode
if the input supply falls to within +50 mV of the battery
voltage. Again, the input supply must rise to a level
150 mV above the battery voltage before the
MCP73831/2 become operational.
The UVLO circuit is always active. At any time the
input supply is below the UVLO threshold or within
+50 mV of the voltage at the VBAT pin, the
MCP73831/2 are placed in a Shutdown mode.
SHUTDOWN MODE
V
< V
DD
UVLO
V
< V
or
DD
BAT
PROG > 200 kΩ
STAT = Hi-Z
During any UVLO condition, the battery reverse
discharge current shall be less than 2 μA.
V
< V
PTH
BAT
4.2
Charge Qualification
PRECONDITIONING
MODE
For a charge cycle to begin, all UVLO conditions must
be met and a battery or output load must be present. A
charge current programming resistor must be
connected from PROG to VSS. If the PROG pin is
open or floating, the MCP73831/2 are disabled and
the battery reverse discharge current is less than 2 μA.
In this manner, the PROG pin acts as a charge enable
and can be used as a manual shutdown.
Charge Current = I
PREG
STAT = LOW
V
> V
PTH
BAT
V
> V
< V
BAT
PTH
RTH
FAST CHARGE
MODE
V
Charge Current = I
BAT
REG
STAT = LOW
4.3
Preconditioning
If the voltage at the VBAT pin is less than the precondi-
tioning threshold, the MCP73831/2 enter a precondi-
tioning or Trickle Charge mode. The preconditioning
threshold is factory set. Refer to Section 1.0 “Electri-
cal Characteristics” for preconditioning threshold
options and the Product Identification System for
standard options.
V
= V
REG
BAT
CONSTANT VOLTAGE
MODE
Charge Voltage = V
REG
STAT = LOW
I
< I
TERM
In this mode, the MCP73831/2 supply a percentage of
the charge current (established with the value of the
resistor connected to the PROG pin) to the battery.
The percentage or ratio of the current is factory set.
Refer to Section 1.0 “Electrical Characteristics” for
preconditioning current options and the Product
Identification System for standard options.
BAT
CHARGE COMPLETE
MODE
No Charge Current
STAT = HIGH (MCP73831)
STAT = Hi-Z (MCP73832)
When the voltage at the VBAT pin rises above the
preconditioning threshold, the MCP73831/2 enter the
Constant-Current or Fast Charge mode.
FIGURE 4-1:
Flowchart.
4.1 Under Voltage Lockout (UVLO)
4.4
Fast Charge Constant-Current
Mode
An internal UVLO circuit monitors the input voltage
and keeps the charger in Shutdown mode until the
input supply rises above the UVLO threshold. The
UVLO circuitry has a built in hysteresis of 100 mV.
During the Constant-Current mode, the programmed
charge current is supplied to the battery or load. The
charge current is established using a single resistor
from PROG to VSS
maintained until the voltage at the VBAT pin reaches
the regulation voltage, VREG
In the event a battery is present when the input power
is applied, the input supply must rise 150 mV above
the battery voltage before the MCP73831/2 becomes
operational.
. Constant-Current mode is
.
DS21984B-page 10
© 2006 Microchip Technology Inc.