参数资料
型号: LTC4080EMSE
厂商: LINEAR TECHNOLOGY CORP
元件分类: 稳压器
英文描述: 0.8 A BATTERY CHARGE CONTROLLER, 2750 kHz SWITCHING FREQ-MAX, PDSO10
封装: PLASTIC, MSOP-10
文件页数: 4/20页
文件大小: 288K
代理商: LTC4080EMSE
LTC4080
12
4080fa
If the die temperature starts to creep up above 115°C
due to internal power dissipation, the transconductance
amplier, TA, limits the die temperature to approximately
115°C by reducing the charge current. Diode D3 ensures
that TA does not affect the charge current when the die
temperature is below 115°C. In thermal regulation, the
PROG pin voltage continues to give an indication of the
charge current.
In typical operation, the charge cycle begins in constant-
current mode with the current delivered to the battery equal
to 400V/RPROG. If the power dissipation of the LTC4080
results in the junction temperature approaching 115°C,
the amplier (TA) will begin decreasing the charge current
to limit the die temperature to approximately 115°C. As
the battery voltage rises, the LTC4080 either returns to
constant-current mode or enters constant-voltage mode
straight from constant-temperature mode.
Battery Charger Undervoltage Lockout (UVLO)
An internal undervoltage lockout circuit monitors the
input voltage and keeps the battery charger off until VCC
rises above 3.6V and approximately 80mV above the BAT
pin voltage. The 3.6V UVLO circuit has a built-in hysteresis
of approximately 0.6V, and the 80mV automatic shutdown
threshold has a built-in hysteresis of approximately 50mV.
During undervoltage lockout conditions, maximum battery
drain current is 5A and maximum supply current is 10A.
Undervoltage Charge Current Limiting (UVCL)
The battery charger in the LTC4080 includes undervoltage
charge current limiting that prevents full charge current
until the input supply voltage reaches approximately 300mV
above the battery voltage (
ΔVUVCL1).Thisfeatureisparticu-
larly useful if the LTC4080 is powered from a supply with
long leads (or any relatively high output impedance). See
Applications Information section for further details.
Trickle Charge and Defective Battery Detection
At the beginning of a charge cycle, if the battery volt-
age is below 2.9V, the battery charger goes into trickle
charge mode, reducing the charge current to 10% of the
programmed current. If the low battery voltage persists
for one quarter of the total time (1.125 hr), the battery is
assumed to be defective, the charge cycle terminates and
the
CHRG pin output pulses at a frequency of 2Hz with
a 75% duty cycle. If, for any reason, the battery voltage
rises above 2.9V, the charge cycle will be restarted. To
restart the charge cycle (i.e., when the dead battery is
replaced with a discharged battery less than 2.9V), the
charger must be reset by removing the input voltage and
reapplying it or temporarily pulling the
EN_CHRGpinabove
the shutdown threshold.
Battery Charger Shutdown Mode
The LTC4080’s battery charger can be disabled by pulling
the
EN_CHRG pin above the shutdown threshold (V
IH).
In shutdown mode, the battery drain current is reduced
to less than 2A and the VCC supply current to about 5A
provided the regulator is off. When the input voltage is
not present, the battery charger is in shutdown and the
battery drain current is less than 5A.
Power Supply Status Indicator (
ACPR)
The power supply status output has two states: pulldown
and high impedance. The pulldown state indicates that VCC
is above the undervoltage lockout threshold and at least
80mV above the BAT voltage (see Undervoltage Lockout).
When these conditions are not met, the
ACPR pin is high
impedance indicating that the LTC4080 is unable to charge
the battery.
CHRG Status Output Pin
The charge status indicator pin has three states: pulldown,
pulse at 2Hz (see Defective Battery Detection) and high
impedance. The pulldown state indicates that the battery
charger is in a charge cycle. A high impedance state indi-
cates that the charge current has dropped below 10% of
the full-scale current or the battery charger is disabled.
When the timer runs out (4.5 hrs), the
CHRG pin is also
forced to the high impedance state. If the battery charger
is not in constant-voltage mode when the charge current
is forced to drop below 10% of the full-scale current by
UVCL,
CHRG will stay in the strong pulldown state.
Charge Current Soft-Start and Soft-Stop
The LTC4080’s battery charger includes a soft-start circuit
to minimize the inrush current at the start of a charge
cycle. When a charge cycle is initiated, the charge cur-
OPERATIO
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