LTC4010 Datasheet, PDF (12/20 Pages) Linear Integrated Systems – High Efficiency Standalone Nickel Battery Charger

LTC4010
APPLICATIO S I FOR ATIO
selects the battery for system power only if an external DC
source is not present.
coefficient and sufficient power dissipation capability to
avoid self-heating effects is recommended.
Battery Chemistry Selection
The desired battery chemistry is selected by programming
the CHEM pin to the proper voltage. If it is wired to GND,
a set of parameters specific to charging NiMH cells is
selected. When CHEM is left floating, charging is opti-
mized for NiCd cells. The various charging parameters are
detailed in Table 2.
Programming Maximum Charge Times
Connecting the appropriate resistor between the TIMER
pin and GND programs the maximum duration of various
charging states. To some degree, the value should reflect
how closely the programmed charge current matches the
1C rate of targeted battery packs. The maximum fast
charge period is determined by the following equation:
Programming Charge Current
Charge current is programmed using the following
equation:
R_SENSE
=
100mV
I_PROG
R_SENSE is an external resistor connected between the
SENSE and BAT pins. A 1% resistor with a low temperature
R_TIMER
=
t_MAX (Hours)
30 • 10^–6
(^Ω)
Some typical timing values are detailed in Table 3. R_TIMER
should not be less than 15k. The actual time limits used by
the LTC4010 have a resolution of approximately ±30
seconds in addition to the tolerances given the Electrical
Characteristics table. The maximum time period is ap-
proximately 4.3 hours.
Table 2. LTC4010 Charging Parameters
CHEM
BAT
STATE PIN CHEMISTRY TIMER T_MIN T_MAX I_CHRG TERMINATION CONDITION
PC
Both
t_MAX/12 5°C
45°C I_PROG/5 Timer Expires
FC Open
NiCd
t_MAX
5°C
60°C I_PROG –20mV per Cell or 2°C/Minute
GND
NiMH
t_MAX
5°C
60°C I_PROG 1.5°C/Minute for First t_MAX/12 Minutes if Initial
V_CELL < 1.325V
–10mV per Cell or 1°C/Minute After t_MAX/12 Minutes
or if Initial V_CELL > 1.325V
TOC GND
NiMH
t_MAX/3 5°C
60°C I_PROG/10 Timer Expires
AR
Both
5°C 45°C
0
V_CELL < 1.325V
PC: Precharge
FC: Fast Charge (Initial –∆V Termination Hold Off of t_MAX/12 Minutes May Apply)
TOC: Top-Off Charge (Only for NiMH ∆T/∆t FC Termination After Initial t_MAX/12 Period)
AR: Automatic Recharge (Temperature Limits Apply to State Termination Only)
Table 3. LTC4010 Time Limit Programming Examples
R_TIMER
24.9k
33.2k
49.9k
66.5k
100k
TYPICAL FAST
CHARGE RATE
2C
1.5C
1C
0.75C
C/2
PRECHARGE LIMIT
(MINUTES)
3.8
5
7.5
10
15
FAST CHARGE
VOLTAGE STABILIZATION
(MINUTES)
3.8
5
7.5
10
15
FAST CHARGE LIMIT
(HOURS)
0.75
1
1.5
2
3
TOP-OFF
CHARGE
(MINUTES)
15
20
30
40
60
4010p
12