LTC1729 データシートの表示（PDF） - Linear Technology

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LTC1729

Li-Ion Battery Charger Termination Controllers

Linear Technology 

LTC1729 Series

APPLICATIO S I FOR ATIO

State Machine

The state machine is responsible for the following items:

1. When to start and stop the charger. The internal timer

must be initialized every time a new battery is installed

or when the input supply is applied.

2. When a battery is installed, the state machine must

determine if it is a new battery or if the previous battery

has been reinstalled.

3. When a deeply discharged battery is installed, trickle

charge conditioning must take place before the full

charge current.

The state machine diagram is shown in Figure 6. Note that

the Charge state includes the Precondition state, the

charger “ON” state and the Reset mode.

Reset and Hold are the two modes that will cause the

charger to stop charging (VC pin pulled low) and ignore the

state machine. The Reset mode clears all the timers and

forces the state machine to begin in the Charge state

(STATUS pin pulled low). This mode is only activated

momentarily at power-up or when the NTC pin is below the

Reset threshold. The other interrupt condition is called the

Hold mode. When the voltage on the NTC pin is above

2.79V (cold) or below 0.405V (hot), the state machine is

locked in the present state until the NTC pin voltage returns

to the proper range. While in the Hold mode, the charging

is disabled and the timers are frozen.

The charger is enabled only during the charger “ON” state.

There are three ways that the state machine can exit the

charger “ON” state. The first is for a 3-hour time-out which

is denoted as the time > tMAX transition to the Done state.

CHARGE

RESET MODE

IBAT = 0

STATUS = PULL-DOWN

VC = PULL-DOWN

VBAT < VMIN

VBAT > VMIN

PRECONDITION

IBAT = 12mA

STATUS = PULL-DOWN

VC = PULL-DOWN

tMAX = 1HR

VBAT > VMIN

VBAT < VMIN

CHARGER “ON”

IBAT = 1.3mA

STATUS = PULL-DOWN

VC = OPEN

tMAX = 3HR

NOTE: FOR STATUS

PULL-DOWN = HARD:

FOR CURRENT > C/10

PULL-DOWN = 50µA:

FOR CURRENT < C/10 FOR 3SEC

VBAT < VMAX

FOR MORE THAN 1SEC

VBAT > VMAX

PAUSE

IBAT = 0

STATUS = PULL-DOWN

VC = PULL-DOWN

VBAT > VMAX

FOR MORE THAN 1SEC

VBAT < VMAX

FOR MORE THAN 1SEC

NO BAT

IBAT = 0

STATUS = OPEN

VC = PULL-DOWN

TIME > tMAX

DONE

IBAT = 0

STATUS = OPEN

VC = PULL-DOWN

VBAT > VMAX

FOR MORE THAN 1SEC

VNTC > 2.79V OR

VNTC < 0.405V

HOLD MODE

IBAT = 0

STATUS = PREVIOUS STATUS

VC = PULL-DOWN

Figure 6. State Diagram

VNTC < 2.79V AND

VNTC > 0.405V

1729 F06

9

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