ltc4078 Linear Technology Corporation, ltc4078 Datasheet - Page 11

• Manufacturer Part Number: ltc4078
• Description: Dual Input Li-ion Battery Charger With Overvoltage Protection
• Manufacturer: Linear Technology Corporation

OPERATION
This output is strong enough to drive an LED. If no valid
voltage is applied at either pin, the PWR pin is high im-
pedance, indicating that the LTC4078/LTC4078X lack valid
input voltage (see Table 1) to charge the battery.
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
*LTC4078 ONLY
BAT < 4.075V
IN VOLTAGE MODE
I
BAT
FULL CURRENT (BAT > 2.9V)
< I
CHRG STATE: PULLDOWN
1/10TH FULL CURRENT
TERMINATE
NO CHARGE CURRENT
SHUTDOWN MODE
CHRG STATE: Hi-Z
CHRG STATE: Hi-Z
6V > DCIN > 4.15V
STANDBY MODE
AND DCIN > BAT
BATDET < 1.75V
(BAT < 2.9V)*
DCIN POWER REMOVED
Figure 1. LTC4078 State Diagram of a Charge Cycle
(DCIN)
(DCIN)
ENABLE = LOW
YES
YES
NO
NO
NO POWER
POWER APPLIED
the LTC4078/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-
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.
YES
NO
NO
USB POWER REMOVED
ENABLE = HIGH
FULL CURRENT (BAT > 2.9V)
CHRG STATE: PULLDOWN
1/10TH FULL CURRENT
NO CHARGE CURRENT
6V > USBIN > 3.95V
SHUTDOWN MODE
CHRG STATE: Hi-Z
AND USBIN > BAT
CHRG STATE: Hi-Z
STANDBY MODE
AND DCIN > BAT
BATDET < 1.75V
(BAT < 2.9V)*
DCIN > 4.15V
(USBIN)
(USBIN)
LTC4078/LTC4078X
I
IN VOLTAGE MODE
BAT
NO
YES
YES
< I
TERMINATE
4078X F01
BAT < 4.075V
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