MCP73871-2AAI/SS Microchip Technology, MCP73871-2AAI/SS Datasheet - Page 20

• Manufacturer Part Number: MCP73871-2AAI/SS
• Description: USB/AC Battery Charger With Power Path Management 20 SSOP .209in TUBE
• Manufacturer: Microchip Technology

Specifications of MCP73871-2AAI/SS

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

MCP73871
5.0
5.1
5.1.1
The V
device. The MCP73871 device can be supplied by
either AC Adapter (V
pin. The MCP73871 device automatically powers the
system with the Li-Ion battery when the V
present.
5.1.2
For the MCP73871 device, the charge current regula-
tion can be scaled by placing a programming resistor
(R
resistor and the charge current are calculated using
the following equation:
EQUATION 5-1:
The fast charge current is set for maximum charge
current from ac-dc adapter and USB port. The precon-
ditioning current is 10% (0.1C) to the fast charge
current.
5.1.3
The battery charge control output is the drain terminal
of an internal P-channel MOSFET. The MCP73871
device provides constant current and voltage regula-
tion 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.
5.1.4
The MCP73871 device continuously monitors battery
temperature during a charge cycle by measuring the
voltage between the THERM and V
50 µA current source provides the bias for most
common
(NTC) or positive-temperature coefficient (PTC)
thermistors.The current source is controlled, avoiding
measurement sensitivity to fluctuations in the supply
voltage (V
voltage at the THERM pin to factory set thresholds of
DS22090A-page 20
Where:
PROG1
R
PROG
I
REG
IN
) from the PROG1 pin to V
DETAILED DESCRIPTION
Analog Circuitry
input is the input supply to the MCP73871
DD
10 kΩ
LOAD SHARING AND LI-ION
BATTERY MANAGEMENT INPUT
SUPPLY (V
FAST CHARGE CURRENT
REGULATION SET (PROG1)
BATTERY CHARGE CONTROL
OUTPUT (V
TEMPERATURE QUALIFICATION
(THERM)
). The MCP73871 device compares the
=
=
I
kilo-ohms (kΩ)
milliampere (mA)
negative-temperature
REG
AC
) or USB Port (V
IN
=
BAT
)
---------------- -
R
1000V
)
PROG
SS
SS
pins. An internal
. The program
USB
IN
input is not
) with SEL
coefficient
1.24V and 0.25V, typically. Once a voltage outside the
thresholds is detected during a charge cycle, the
MCP73871 device immediately suspends the charge
cycle.
The MCP73871 device suspends charge by turning off
the pass transistor and holding the timer value. The
charge cycle resumes when the voltage at the THERM
pin returns to the normal range.
If temperature monitoring is not required, place a
standard 10 kΩ resistor from THERM to V
5.2
5.2.1
The charge status outputs have two different states:
Low (L), and High Impedance (Hi-Z). The charge status
outputs can be used to illuminate LEDs. Optionally, the
charge status outputs can be used as an interface to a
host microcontroller.
the status outputs during a charge cycle.
TABLE 5-1:
5.2.2
With the SEL input Low, the MCP73871 device is
designed to provide system power and Li-Ion battery
charging from a USB input while adhering to the current
limits governed by the USB specification. The host
microcontroller has the option selecting either a
100 mA (L) or a 500 mA (H) current limit based on the
PROG2 input. With the SEL input High, the MCP73871
device limits the input current to 1.8A. The pro-
grammed charge current is established using a single
resistor from PROG1 to V
Shutdown (V
Shutdown (V
Preconditioning
Constant Current
Constant Voltage
Charge Complete - Standby
Temperature Fault
Timer Fault
Low Battery Output
No Battery Present
No Input Power Present
CHARGE CYCLE STATE
Digital Circuitry
STATUS INDICATORS AND POWER-
GOOD (PG)
AC-DC ADAPTER AND USB PORT
POWER SOURCE REGULATION
SELECT (SEL)
DD
DD
= V
= IN)
STATUS OUTPUTS
BAT
Table 5-1
)
© 2008 Microchip Technology Inc.
SS
STAT1
when driving SEL High.
Hi-Z
Hi-Z
Hi-Z
Hi-Z
Hi-Z
summarizes the state of
L
L
L
L
L
L
STAT2
Hi-Z
Hi-Z
Hi-Z
Hi-Z
Hi-Z
Hi-Z
Hi-Z
Hi-Z
L
L
L
SS
Hi-Z
Hi-Z
Hi-Z
PG
L
L
L
L
L
L
L
L