LTC4066/LTC4066-1
APPLICATIONS INFORMATION
Current Limit Undervoltage Lockout
An internal undervoltage lockout circuit monitors the
input voltage and disables the input current limit circuits
until VIN rises above the undervoltage lockout threshold.
The current limit UVLO circuit has a built-in hysteresis of
125mV. Furthermore, to protect against reverse current in
the power MOSFET, the current limit UVLO circuit disables
the current limit (i.e., forces the input power path to a high
impedance state) if VOUT exceeds VIN. If the current limit
UVLO comparator is tripped, the current limit circuits will
not come out of shutdown until VOUT falls 50mV below
the VIN voltage.
Charger Undervoltage Lockout
An internal undervoltage lockout circuit monitors the VOUT
voltage and disables the battery charger circuits until
VOUT rises above the undervoltage lockout threshold. The
battery charger UVLO circuit has a built-in hysteresis of
125mV. Furthermore, to protect against reverse current
in the power MOSFET, the charger UVLO circuit keeps the
chargershutdownifVBAT exceedsVOUT.IfthechargerUVLO
comparator is tripped, the charger circuits will not come
out of shutdown until VOUT exceeds VBAT by 50mV.
Shutdown
The LTC4066/LTC4066-1 can be shutdown by forcing the
SHDN pin greater than 1.2V. In shutdown, the currents
drawn from IN, OUT and BAT are decreased to less than
2.5μA and the internal battery charge timer and end-of-
charge comparator output are reset. All power paths are
put in a high impedance state.
Suspend
The LTC4066/LTC4066-1 can be put in suspend mode by
forcing the SUSP pin greater than 1.2V. In suspend mode
the ideal diode function from BAT to OUT is kept alive.
If power is applied to the OUT pin externally (i.e., a wall
adapter is present) then charging will be unaffected. Current
drawn from the IN pin is reduced to 50μA. Suspend mode
is intended to comply with the USB Power Specification
mode of the same name.
Selecting WALL Input Resistors
The WALL input pin identifies the presence of a wall adapter.
This information is used to disconnect the input pin, IN,
from the OUT pin in order to prevent back conduction to
whatever may be connected to the input. It also forces the
ACPR pin low when the voltage at the WALL pin exceeds
the input threshold. The WALL pin has a 1.225V rising
threshold and approximately 30mV of hysteresis.
The wall adapter detection threshold is set by the follow-
ing equation:
VTH(Adapter) = VWALL • ⎛⎝⎜1+ RR21⎞⎠⎟
VHYST(Adapter) = VWALL(HYST) • ⎛⎝⎜1+ RR21⎞⎠⎟
where VTH(Adapter) is the wall adapter detection threshold,
VWALL is the WALL pin rising threshold (typically 1.225V),
R1 is the resistor from the wall adapter input to WALL and
R2 is the resistor from WALL to GND.
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