Datasheet

LTC4150
10
4150fc
APPLICATIONS INFORMATION
AUTOMATIC CHARGE COUNT INTERRUPT AND CLEAR
In applications where a CLR p u l s e i s u n a v a i l a b l e , i t ’s e a s y t o
make the LTC4150 run autonomously, as shown in Figures
5 and 6. If the microcontroller V
CC
is less than or equal to
the battery V
DD
, INT may be directly connected to CLR, as
in Figure 5. The only requirement is that the microcontroller
s h o u l d b e a b l e t o p r o v i d e a h i g h l o g i c l e v e l o f 1. 9 V t o SHDN.
If the microcontroller V
CC
is greater than the battery V
DD
,
use Figure 6. The resistor dividers on CLR and SHDN keep
the voltages at these pins within the LTC4150’s V
DD
range.
Choose an R
L
value using Equation 11 and R1-R4 values
using Equation 13. In either application, the LTC4150 will
capture the fi rst assertion of INT and wait at least 1μs
before resetting it. This insures that INT pulses low for at
least 1μs but gives automatic INT reset.
INTSENSE
+
SENSE
–
SHDN
CLR
POL
LTC4150
μP
C2
4.7μF
R
L
10
9
8
7
6
1
2
5
4150 F05
V
DD
GND
R
L
PROCESSOR
V
CC
POWER-DOWN
SWITCH
C
L
47μF
LOAD
+
C
F
+
C
F
–
3
4
C
F
4.7μF
2.7V TO 8.5V
BATTERY
R
SENSE
INTSENSE
+
SENSE
–
SHDN
SHUTDOWN
R4
R3
CLR
POL
LTC4150
μP
C2
4.7μF
R
L
10
9
8
7
6
1
2
5
4150 F06
V
DD
GND
R
L
PROCESSOR
V
CC
POWER-DOWN
SWITCH
C
L
47μF
LOAD
+
C
F
+
C
F
–
3
4
C
F
4.7μF
BATTERY
V
BATTERY
< V
CC
R
SENSE
R2
R1
Figure 5. Application with INT Direct Drive or CLR and Separate Microprocessor Supply V
CC
≤ V
DD
Figure 6. Application with INT Driving CLR and Separate Microprocessor Supply V
CC
> V
DD