LTC4011 Linear Technology, LTC4011 Datasheet - Page 14

• Manufacturer Part Number: LTC4011
• Description: High Efficiency Standalone Nickel Battery Charger
• Manufacturer: Linear Technology

www.DataSheet4U.com
DataSheet U .com
APPLICATIO S I FOR ATIO
LTC4011
Cell Voltage Network Design
An external resistor network is required to provide the
average single-cell voltage to the V
The proper circuit for multicell packs is shown in Figure 3.
The ratio of R2 to R1 should be a factor of (n – 1), where
n is the number of series cells in the battery pack. The value
of R1 should be between 1k and 100k. This range limits the
sensing error caused by V
vents the ON resistance of the internal NFET between V
and GND from causing a significant error in the V
voltage. The external resistor network is also used to
detect battery insertion and removal. The filter formed by
C1 and the parallel combination of R1 and R2 is recom-
mended for rejecting PWM switching noise. The value of
C1 should be chosen to yield a 1st order lowpass fre-
quency of less than 500Hz. In the case of a single cell, the
14
4
Table 3. LTC4011 Time Limit Programming Examples
Table 2. LTC4011 Charging Parameters
PC: Precharge
FC: Fast Charge (Initial –∆V Termination Hold Off of t
TOC: Top-Off Charge (Only for NiMH ∆T/∆t FC Termination After Initial t
AR: Automatic Recharge (Temperature Limits Apply to State Termination Only)
R
24.9k
33.2k
49.9k
66.5k
100k
STATE
TIMER
TOC
PC
AR
FC
CHEM
Open
GND
GND
PIN
U
TYPICAL FAST
CHARGE RATE
0.75C
1.5C
C/2
2C
1C
CHEMISTRY TIMER
U
CELL
NiMH
NiMH
NiCd
Both
Both
BAT
leakage current and pre-
CELL
W
t
PRECHARGE LIMIT
t
MAX
MAX
t
t
MAX
MAX
pin of the LTC4011.
(MINUTES)
/12
/3
3.8
7.5
10
15
5
T
5°C
5°C
5°C
5°C
5°C
MIN
U
MAX
CELL
CDIV
T
45°C
60°C
60°C
60°C
45°C
/12 Minutes May Apply)
MAX
VOLTAGE STABILIZATION
FAST CHARGE
I
I
PROG
PROG
(MINUTES)
I
I
I
external application circuit shown in Figure 4 is recom-
mended to provide the necessary noise filtering and miss-
ing battery detection.
CHRG
PROG
PROG
0
MAX
/10
3.8
7.5
10
15
/5
5
/12 Period)
TERMINATION CONDITION
Timer Expires
–20mV per Cell or 2°C/Minute
1.5°C/Minute for First t
V
–10mV per Cell or 1°C/Minute After t
or if Initial V
Timer Expires
V
CELL
CELL
Figure 3. Mulitple Cell Voltage Divider
< 1.325V
< 1.325V
LTC4011
CELL
FAST CHARGE LIMIT
> 1.325V
V
V
CELL
CDIV
GND
BAT
(HOURS)
0.75
1.5
MAX
1
2
3
12
8
9
5
4011 F03
/12 Minutes if Initial
MORE SERIES CELLS
R2
R1
R2 = R1(n – 1)
FOR TWO OR
MAX
+
/12 Minutes
(MINUTES)
C1
TOP-OFF
CHARGE
15
20
30
40
60
4011p