LTC4060
U
OPERATIO
The LTC4060 is a complete linear fast charging system for
NiMH or NiCd batteries. Operation can be understood by
referring to the Block Diagram, State Diagram (Figure 1)
and application circuit (Figure 2). While in the unpowered
sleep mode, the battery is disconnected from any internal
loading. The sleep mode is exited and the shutdown mode
is entered when VCC rises above the UVLO (Undervoltage
Lock Out) exit threshold. The UVLO thresholds are depen-
dent upon the number of series cells programmed by the
SEL0 and SEL1 pins. When shutdown occurs the ACP pin
goes from a high to low impedance state. The shutdown
mode is exited and the charge qualification mode entered
when all of the following conditions are met: 1) there is no
manual shutdown command from SHDN, 2) the battery
overvoltage detector does not detect a battery overvolt-
age, 3) the battery removal detector detects a battery in
place,4)pauseisinactiveand5)theIC’sjunctiontempera-
ture is normal. Once in the charge qualification mode the
thermistor interface monitors an optional thermistor net-
work to determine if the battery temperature is within
charging limits. If the temperature is found within limits
charging can begin. While charging, the CHRG pin pulls to
GND which can drive an LED.
MANUAL
SHUTDOWN
(SHDN = 0)
SUPPLY
GOOD
(ACP = 0)
BATTERY REMOVED,
BATTERY OVERVOLTAGE,
LOW OR NO
SLEEP
SHUTDOWN
CHARGE PERIOD TIMED
OUT OR IC TOO HOT
SUPPLY
ADEQUATE SUPPLY
AND CHARGER ENABLED
CHARGE
QUALIFICATION
BATTERY PRESENT AND
TEMPERATURE GOOD
(OPTIONAL)
V
< AUTORECHARGE
THRESHOLD
CELL
PRECHARGE
(I /5)
MAX
ADEQUATE V
TEMPERATURE GOOD
(OPTIONAL)
AND
CELL
–∆V TERMINATION
AUTOMATIC
RECHARGE
FAST CHARGE
(I
)
MAX
4060 F01
Figure 1. LTC4060 Basic State Diagram
4060f
8
Linear Systems [ Linear Systems ]
