LTC4060_15 Datasheet, PDF (8/20 Pages) Linear Technology – Standalone Linear NiMH/NiCd Fast Battery Charger

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 V_CC 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) pause is inactive and 5) the IC’s junction tempera-
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)
LOW OR NO
SUPPLY
SLEEP
SUPPLY
GOOD
(ACP = 0)
SHUTDOWN
BATTERY REMOVED,
BATTERY OVERVOLTAGE,
CHARGE PERIOD TIMED
OUT OR IC TOO HOT
ADEQUATE SUPPLY
AND CHARGER ENABLED
8
CHARGE
QUALIFICATION
V_CELL < AUTORECHARGE
THRESHOLD
BATTERY PRESENT AND
TEMPERATURE GOOD
(OPTIONAL)
PRECHARGE
(I_MAX/5)
ADEQUATE V_CELL AND
TEMPERATURE GOOD
(OPTIONAL)
–∆V TERMINATION
AUTOMATIC
RECHARGE
FAST CHARGE
(I_MAX)
4060 F01
Figure 1. LTC4060 Basic State Diagram
4060f