LTC4006 Linear Technology, LTC4006 Datasheet - Page 8

• Manufacturer Part Number: LTC4006
• Description: Standalone Li-Ion Battery Charger
• Manufacturer: Linear Technology

OPERATIO
*Open Drain. High when used with pull-up resistor.
**Most probable condition, X = Don’t care
LTC4006
Table 1. Truth Table for LTC4006 Operation
MODE
Shut Down by Low Adapter Voltage
Conditioning a Depleted Battery
Normal Charging
Input Current Limited Charging
Charger Paused Due to Thermistor Out of Range
Shut Down by ACP/SHDN Pin
Terminated by Low-Battery Fault (Note 1)
Top-Off Charging. C/10 is Latched
Timer is Reset by C/10 Comparator (Latched),
then Terminates After 1/4 T
Terminated by Expired Timer
Timer Defeated. (Low-Battery Conditioning Still
Functional)
Shut Down by Undervoltage Lockout
Timer Defeated Until V
therefore,
The voltage at BAT is divided down by an internal resistor
divider and is used by error amp EA to decrease I
divider voltage is above the 1.19V reference. When the
charging current begins to decrease, the voltage at I
will decrease in direct proportion. The voltage at I
then given by:
V
The amplifier CL1 monitors and limits the input current to
a preset level (100mV/R
decrease the I
rent. When this condition is detected, the C/10 indicator
8
IMON
V
I
CHARGE
IMON
is plotted in Figure 2.
I
CHARGE
TH
R
V
IMON
voltage, thereby reducing charging cur-
BAT
REF
U
> 3.9V/Cell
•
R
–
SENSE
CL
11 67
). At input current limit, CL1 will
.
11 67
A
.
•
R
3
SENSE
and <UVL
k
A
<BAT
>BAT
>BAT
>BAT
>BAT
>BAT
>BAT
>BAT
>BAT
>BAT
>BAT
>BAT
DCIN
•
X
3
k
•
2.5V V
TH
R
MON
BAT VOLTAGE
3
IMON
if the
<2.5V/Cell
>2.5V/Cell
>2.5V/Cell
<2.5V/Cell
k
V
MON
(V/Cell)
>UVLO
V
V
FLOAT
<UVL
FLOAT
FLOAT
is
X
X
X
BAT
**
3.9V
Note 1: If a depleted battery is inserted while the charger is in this state,
the charger must be reset to initiate charging.
will be inhibited if it is not already active. If the charging
current decreases below 10% to 15% of programmed
current, while engaged in input current limiting, BGATE
will be forced low to prevent the charger from discharging
the battery. Audible noise can occur in this mode of
operation.
An overvoltage comparator guards against voltage tran-
sient overshoots (>7% of programmed value). In this
case, both MOSFETs are turned off until the overvoltage
condition is cleared. This feature is useful for batteries
which “load dump” themselves by opening their protec-
tion switch to perform functions such as calibration or
pulse mode charging.
As the voltage at BAT increases to near the input voltage
at DCIN, the converter will attempt to turn on the top
MOSFET continuously (“dropout’’). A watchdog timer
detects this condition and forces the top MOSFET to turn
10% Programmed
BAT CURRENT
Programmed
Programmed
Unknown
Leakage
Current
Current
Current
OFF
OFF
OFF
OFF
OFF
OFF
OFF
X
Forced LOW
ACP/SHDN
HIGH
HIGH
HIGH
HIGH
HIGH
HIGH
HIGH
HIGH
HIGH
HIGH
LOW
X
Comparator Trip.
Comparator Trip.
<T/4 After C/10
>T/4 After C/10
TIMER STATE
>T/4 Stopped
>T Stopped
Running
Running
Running
Running
Stopped
Running
Paused
Reset
Reset
Reset
X
Forced LOW
for Restart)
for Restart)
(Faulted)
(Faulted)
(Waiting
(Waiting
HIGH**
sn4006 4006is
CHG*
HIGH
HIGH
HIGH
25 A
HIGH
HIGH
LOW
LOW
LOW
LOW
LOW