Datasheet
LTC4020
35
4020fd
For more information www.linear.com/LTC4020
applicaTions inForMaTion
LTC4020 Lead-Acid Charging Diagram
POWER
AVAILABLE?
INDICATE NOT
CHARGING
BGATE PULLED
LOW
SET ABSORPTION
REFERENCE (2.5V)
V
FB
< 2.5 – ε?
V
FB
< 1.75?
V
FB
> 1.75?
YES
NO
NO NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
YES
4020 CD02
NO
YES
YES
YES
YES
YES
YES
V
FB
< 2.125?
V
FB
= 2.4375V
NTC
OUT-OF-RANGE?
CHARGE AT
CONSTANT-CURRENT
BGATE PULLED LOW
SET ABSORPTION
REFERENCE (2.5V)
TIMER ACTIVE?
STOP CHARGING
BGATE PULLED HIGH
INDICATE NOT
CHARGING
INDICATE NOT
CHARGING
ENABLE IDEAL
DIODE FUNCTION
TIMERS ACTIVE?
PAUSE TIMERS
CHARGE TO FIXED
VOLTAGE
TIMER ACTIVE?
RUN SAFETY TIMER
SAFETY TIMER
AT EOC?
SET FLOAT
REFERENCE
(2.3125V)
INDICATE FLOAT
CHARGING
STOP CHARGING
I
BAT
< C/10?
I
BAT
< C/10?
START
CLEAR LOW BATTERY
AND SAFETY TIMERS
TRICKLE
CHARGE (7%)
INDICATE BULK
CHARGING
INDICATE
ABSORPTION
CHARGING
INDICATE BULK
CHARGING
FLOAT
REFERENCE SET
(2.3125)?
YES
YES
YES
NO
YES
YES
YES
YES
RUN LOW
BATTERY TIMER
TIMER AT 1/8
EOC?
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