LTC4006_15 Datasheet, PDF (9/20 Pages) Linear Technology – 4A, High Efficiency, Standalone Li-Ion Battery Charger

LTC4006
U
OPERATIO
Table 1. Truth Table for LTC4006 Operation
MODE
DCIN
Shut Down by Low Adapter Voltage
<BAT
Conditioning a Depleted Battery
>BAT
Normal Charging
>BAT
Input Current Limited Charging
>BAT
Charger Paused Due to Thermistor Out of Range >BAT
Shut Down by ACP/SHDN Pin
Terminated by Low-Battery Fault (Note 1)
>BAT
>BAT
Top-Off Charging. C/10 is Latched
>BAT
Timer is Reset by C/10 Comparator (Latched),
then Terminates After 1/4 T
Terminated by Expired Timer
>BAT
>BAT
Timer Defeated. (Low-Battery Conditioning Still
Functional)
Shut Down by Undervoltage Lockout
Timer Defeated Until V_BAT > 3.9V/Cell
X
>BAT
and <UVL
>BAT
BAT VOLTAGE
>UVLO
<2.5V/Cell
>2.5V/Cell
>2.5V/Cell
X
X
<2.5V/Cell
V_FLOAT
V_FLOAT
V_FLOAT**
X
<UVL
2.5V ≤ V_BAT ≤3.9V
(V/Cell)
BAT CURRENT
Leakage
10% Programmed
Current
Programmed
Current
Programmed
Current
OFF
OFF
OFF
OFF
OFF
OFF
X
OFF
Programmed
Current
ACP/SHDN
LOW
HIGH
HIGH
HIGH
HIGH
Forced LOW
HIGH
HIGH
HIGH
HIGH
X
HIGH
HIGH
TIMER STATE
Reset
Running
Running
Running
Paused
Reset
>T/4 Stopped
<T/4 After C/10
Comparator Trip.
Running
>T/4 After C/10
Comparator Trip.
Stopped
>T Stopped
X
Reset
Running
CHG*
HIGH
LOW
LOW
LOW
LOW or 25µA
(Faulted)
HIGH
HIGH
(Faulted)
25µA
HIGH
(Waiting
for Restart)
HIGH
(Waiting
for Restart)
Forced LOW
HIGH**
LOW
*Open Drain. High when used with pull-up resistor.
**Most probable condition, X = Don’t care
Note 1: If a depleted battery is inserted while the charger is in this state,
the charger must be reset to initiate charging.
compares this current against the desired current programmed
by R_IMON at the I_MON pin and adjusts I_TH until:
V_{REF =} V_CSP – V_BAT + 11.67µA • 3kΩ
R_IMON
3kΩ
therefore,
I_CHARGE
=
⎛
⎝⎜
V_REF
R_IMON
–
11.67µA^{⎞⎠⎟}
•
3kΩ
R_SENSE
The voltage at BAT is divided down by an internal resistor
divider and is used by error amp EA to decrease I_TH if the
divider voltage is above the 1.19V reference. When the
charging current begins to decrease, the voltage at I_MON
will decrease in direct proportion. The voltage at I_MON is
then given by:
( ) ^V_IMON ⁼
I_CHARGE •R_SENSE + 11.67µA • 3kΩ
• ^RIMON
3kΩ
The accuracy of V_IMON will range from 0% to I_TOL.
V_IMON is plotted in Figure 2.
The amplifier CL1 monitors and limits the input current to
a preset level (100mV/R_CL). At input current limit, CL1 will
decrease the I_TH voltage, thereby reducing charging cur-
rent. When this condition is detected, the C/10 indicator will
1.2
1.19V
1.0
0.8
0.6
0.4
0.309V
0.2
0
0
20
40
60
80 100
I_CHARGE (% OF MAXIMUM CURRENT)
4006 F02
Figure 2. V_IMON vs I_CHARGE
4006fa
9