LTC4060
U
TYPICAL APPLICATIO S
Full Featured 2A Charger Application
Power Path Control
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.
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 VIN is
applied the forward biased Schottky diode will power the
load while the P-channel FET will disconnect the battery
from the load. When VIN is removed, the FET will turn-on
to provide a low loss switch from the battery to the load,
and the diode will isolate VIN. The ACP output signals the
presense of VIN.
The PROG pin has a total resistance of 691Ω to ground
thatprogramsthefast-chargecurrentatthePNP’semitter
to2.02A(2Aatthecollectorforbetaof100). TheARCTpin
voltage is programmed to 1.25V. When the battery cell
voltage falls below this automatic recharge will begin.
Optional capacitor CBAT filters excessive contact bounce.
This circuit can be modified to charge a 4A-Hr battery at a
C/2 rate simply by doubling the CTIMER capacitance.
V
= 5V
IN
R
LED
14
CC
330Ω
R
R
LED
330Ω
HOT
V
4.42k
“AC”
5
15
11
13
3
SHDN
ACP
“CHARGE”
CHRG SENSE
1
NTC
DRIVE
MJD210
LTC4060
7
8
2
R
NTC
PROG
ARCT
SEL0
SEL1
BAT
TIMER
CHEM
PAUSE
+ 2-CELL
NiMH
BATTERY
10k
C
4
R
BAT
PROG
10µF
115Ω
9
12
6
C
TIMER
R
10
ARCT
1.5nF
576Ω
GND
4060 F02
16
Figure 2. Full Featured 2A Charger Application
V
= 5V
IN
B220A
R
R
LED
AC
V
330Ω
CC
10k
5
15
11
13
3
SHDN
ACP
ACP
“CHARGE”
CHRG SENSE
1
FDG312P
NTC
DRIVE
FZT948
LTC4060
7
8
2
PROG
ARCT
SEL0
SEL1
BAT
TIMER
CHEM
PAUSE
TO LOAD
+ 2-CELL
NiMH
BATTERY
R
PROG
4
C
LOAD
1400Ω
10µF
*
9
12
6
4060 F03
10
C
TIMER
820pF
GND
*DRAIN SOURCE DIODE OF MOSFET
16
Figure 3. 1A Charger Application with Power Path Control
4060f
16
Linear Systems [ Linear Systems ]
