LTC4078X

11

4078xf

SHUTDOWN MODE

(USBIN)

CHRG STATE: Hi-Z

CHARGE MODE

(DCIN)

FULL CURRENT

CHRG STATE: PULLDOWN

CHARGE MODE

(USBIN)

FULL CURRENT

CHRG STATE: PULLDOWN

STANDBY MODE

(DCIN)

NO CHARGE CURRENT

CHRG STATE: Hi-Z

SHUTDOWN MODE

(DCIN)

CHRG STATE: Hi-Z

YES

NO

BAT < 4.075V

BAT < 4.075V

IN VOLTAGE MODE

IN VOLTAGE MODE

NO POWER

STANDBY MODE

(USBIN)

NO CHARGE CURRENT

CHRG STATE: Hi-Z

YES

NO

NO

YES

BATDET < 1.75V

BATDET < 1.75V

NO

YES

NO

6V > USBIN > 3.95V

AND USBIN > BAT

YES

DCIN > 4.15V

AND DCIN > BAT

6V > DCIN > 4.15V

AND DCIN > BAT

ENABLE = LOW

ENABLE = HIGH

POWER APPLIED

DCIN POWER REMOVED

USB POWER REMOVED

4078X F01

Thermal Limiting

An internal thermal feedback loop reduces the programmed

charge current if the die temperature attempts to rise

above a preset value of approximately 120°C. This feature

protects the LTC4078X from excessive temperature and

allows the user to push the limits of the power handling

capability of a given circuit board without risk of damag-

OPERATION

Figure 1. LTC4078X State Diagram of a Charge Cycle

ing the device. The charge current can be set according

to typical (not worst-case) ambient temperature with the

assurance that the charger will automatically reduce the

current in worst case conditions. DFN package power

considerations are discussed further in the Applications

Information section.