Datasheet
16
LTC4060
4060f
TYPICAL APPLICATIO S
U
Full Featured 2A Charger Application
Figure 2 shows an application that utilizes the optional
temperature sensing and optional externally program-
mable automatic recharge features. It also has LEDs to
indicate charging status and the presence of sufficient
input supply voltage.
The PROG pin has a total resistance of 691Ω to ground
that programs the fast-charge current at the PNP’s emitter
to 2.02A (2A at the collector for beta of 100). The ARCT pin
voltage is programmed to 1.25V. When the battery cell
voltage falls below this automatic recharge will begin.
Optional capacitor C
BAT
filters excessive contact bounce.
This circuit can be modified to charge a 4A-Hr battery at a
C/2 rate simply by doubling the C
TIMER
capacitance.
Power Path Control
Proper power path control is an important consideration
when fast charging nickel cells. This control ensures the
system load remains powered at all times, but that normal
system operation and associated load transients do not
adversely affect the charging procedure. Figure 3 illus-
trates a 1A charger with power path control. When V
IN
is
applied the forward biased Schottky diode will power the
load while the P-channel FET will disconnect the battery
from the load. When V
IN
is removed, the FET will turn-on
to provide a low loss switch from the battery to the load,
and the diode will isolate V
IN
. The ACP output signals the
presense of V
IN
.
V
CC
V
IN
=
5V
LTC4060
GND
SHDN
CHRG
NTC
PROG
ARCT
SEL0
SEL1
ACP
SENSE
DRIVE
BAT
TIMER
CHEM
PAUSE
5
15
11
7
8
9
10
13
3
1
2
4
12
6
R
LED
330Ω
R
LED
330Ω
R
HOT
4.42k
R
NTC
10k
R
PROG
115Ω
R
ARCT
576Ω
C
TIMER
1.5nF
16
14
4060 F02
C
BAT
10µF
2-CELL
NiMH
BATTERY
“CHARGE”
“AC”
MJD210
+
V
CC
V
IN
=
5V
FDG312P
B220A
LTC4060
GND
SHDN
CHRG
NTC
PROG
ARCT
SEL0
SEL1
ACP
SENSE
DRIVE
BAT
TIMER
CHEM
PAUSE
R
LED
330Ω
R
PROG
1400Ω
C
TIMER
820pF
16
R
AC
10k
4060 F03
C
LOAD
10µF
*DRAIN SOURCE DIODE OF MOSFET
2-CELL
NiMH
BATTERY
“CHARGE”
FZT948
ACP
TO LOAD
*
5
15
11
7
8
9
10
13
3
1
2
4
12
6
+
Figure 2. Full Featured 2A Charger Application
Figure 3. 1A Charger Application with Power Path Control