Datasheet

9
LTC4006
4006fa
OPERATIO
U
compares this current against the desired current programmed
by R
IMON
at the I
MON
pin and adjusts I
TH
until:
V
R
VV Ak
k
REF
IMON
CSP BAT
=
+µΩ
Ω
–.•11 67 3
3
therefore,
I
V
R
A
k
R
CHARGE
REF
IMON SENSE
=µ
⎛
⎝
⎜
⎞
⎠
⎟
Ω
–. •11 67
3
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:
VI R Ak
R
k
IMON CHARGE SENSE
IMON
=+µΩ
()
Ω
•.••11 67 3
3
Table 1. Truth Table for LTC4006 Operation
MODE DCIN BAT VOLTAGE BAT CURRENT ACP/SHDN TIMER STATE CHG*
Shut Down by Low Adapter Voltage <BAT >UVLO Leakage LOW Reset HIGH
Conditioning a Depleted Battery >BAT <2.5V/Cell 10% Programmed HIGH Running LOW
Current
Normal Charging >BAT >2.5V/Cell Programmed HIGH Running LOW
Current
Input Current Limited Charging >BAT >2.5V/Cell Programmed HIGH Running LOW
Current
Charger Paused Due to Thermistor Out of Range >BAT X OFF HIGH Paused LOW or 25µA
(Faulted)
Shut Down by ACP/SHDN Pin >BAT X OFF Forced LOW Reset HIGH
Terminated by Low-Battery Fault (Note 1) >BAT <2.5V/Cell OFF HIGH >T/4 Stopped HIGH
(Faulted)
Top-Off Charging. C/10 is Latched >BAT V
FLOAT
OFF HIGH <T/4 After C/10 25µA
Comparator Trip.
Running
Timer is Reset by C/10 Comparator (Latched), >BAT V
FLOAT
OFF HIGH >T/4 After C/10 HIGH
then Terminates After 1/4 T Comparator Trip. (Waiting
Stopped for Restart)
Terminated by Expired Timer >BAT V
FLOAT
** OFF HIGH >T Stopped HIGH
(Waiting
for Restart)
Timer Defeated. (Low-Battery Conditioning Still X X X X X Forced LOW
Functional)
Shut Down by Undervoltage Lockout >BAT <UVL OFF HIGH Reset HIGH**
and <UVL
Timer Defeated Until V
BAT
> 3.9V/Cell >BAT 2.5V ≤ V
BAT
≤3.9V Programmed HIGH Running LOW
(V/Cell) Current
*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.
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
Figure 2. V
IMON
vs I
CHARGE
I
CHARGE
(% OF MAXIMUM CURRENT)
0
0
V
IMON
(V)
0.2
0.4
0.6
0.8
4006 F02
1.0
1.2
20 40 60 80 100
1.19V
0.309V