U
OPERATIO
Status Indicators
The charge status output (C⎯ H⎯ R⎯ G⎯ ) has two states: pull-down
and high impedance. The pull-down state indicates that
the LTC4077 is in a charge cycle. Once the charge cycle
has terminated or the LTC4077 is disabled, the pin state
becomes high impedance. The pull-down state is capable
of sinking up to 10mA.
LTC4077
The power supply status output (⎯P⎯W⎯R) has two states:
pull-down and high impedance. The pull-down state
indicates that power is present at either DCIN or USBIN.
If no power is applied at either pin, the ⎯P⎯W⎯R pin is high
impedance, indicating that the LTC4077 lacks sufficient
power to charge the battery. The pull-down state is capable
of sinking up to 10mA.
STARTUP
BAT < 2.9V
DCIN POWER APPLIED
ONLY USB POWER APPLIED
POWER SELECTION
TRICKLE CHARGE
MODE
1/10th FULL CURRENT
CHRG STATE: PULLDOWN
DCIN POWER
REMOVED
USBIN POWER
REMOVED OR
DCIN POWER
APPLIED
TRICKLE CHARGE
MODE
1/2 OR 1/10th FULL CURRENT
CHRG STATE: PULLDOWN
BAT < 2.9V
BAT > 2.9V
BAT > 2.9V
2.9V < BAT
CHARGE
MODE
FULL CURRENT
CHRG STATE: PULLDOWN
IBAT < ITERMINATE
IN VOLTAGE MODE
CHARGE
MODE
FULL CURRENT
CHRG STATE: PULLDOWN
2.9V < BAT
IBAT < ITERMINATE
IN VOLTAGE MODE
BAT < 4.1V
STANDBY
MODE
NO CHARGE CURRENT
CHRG STATE: Hi-Z
STANDBY
MODE
NO CHARGE CURRENT
CHRG STATE: Hi-Z
BAT < 4.1V
EN
DRIVEN LOW
SHUTDOWN
MODE
IDCIN DROPS TO 20mA
CHRG STATE: Hi-Z
EN
DRIVEN HIGH
DCIN POWER
REMOVED
EN
DRIVEN HIGH
USBIN POWER
REMOVED OR
DCIN POWER
APPLIED
SHUTDOWN
MODE
IUSBIN DROPS TO 18mA
CHRG STATE: Hi-Z
EN
DRIVEN LOW
4075 F01
Figure 1. LTC4077 State Diagram of a Charge Cycle
4077f
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