Datasheet

9
LTC1540
sn1540 1540fas
Low-Battery Detect
Figure 9 shows how to use the LTC1540 for a low-battery
detect, drawing only 1.4µA at V
BAT
= 2V. The circuit is
powered by a 2-cell NiCd battery. The V
BAT
pin could be as
low as 1.6V when the batteries are completely depleted.
The electrical specifications of the LTC1540 guarantee
operation down to a supply voltage of 2V, but it is still
functional with the supply as low as 1.6V. Some param-
eters, such as V
REF
and V
OS
, will be degraded on lower
supply voltages. The input voltage range extends from
0.9V below the positive supply to the negative supply.
TYPICAL APPLICATIONS
U
Figure 9. Low-Battery Detect Works Down to 1.6V
V
+
R1
3M
R2
1.1M
V
BAT
= ~1.6V TO 2.5V
V
–
21
7
8
OUT
GND
LBO
2-CELL
NiCd
LTC1540
1540 F09
IN
+
IN
–
REF
HYST
3
4
6
5
–
+
R3
40k
R4
1.2M
R5
1M