9

LTC1440/LTC1441/LTC1442

2. Calculate the required resistive divider ratio.

Ratio = 1.182V/4.65V = 0.254

3. Choose the required hysteresis voltage band at the

4. Choose the values for R3 and R4 to set the hysteresis.

R4 = 2.4M

R3(k

5. Choose the values for R1 and R2 to set the trip point.

R

V

I

V

A

M

RR

V

V

V

REF

BIAS

IN

REF

HB

1

1 182

1

118

21

2

1

==

=

=

+

−

























.

.

µ

RM

V

V

mV

RM

21 18

465

1 182

15

2

1

23 40

=

+

−

























=

.

.

.

.

Low Voltage Operation

The guaranteed minimum operating voltage is 2V or

(

±1V). As the total supply voltage is reduced below 2V, the

performance degrades and the supply current falls. Both

the reference and the comparator are still functioning with

supply voltage down to 1.5V. The reference will have

slightly worse temperature coefficient. While the com-

parator would have less output drive and the propagation

delay increases. The useful input voltage range extends

from the negative supply to a little under 1V below the

positive supply, which is slightly closer to the positive rail

than the device operating from higher supply voltages.

2.6M

2-CELL

NiCd

1M

2

1

7

8

6

5

GND

HYST

REF

OUT

LTC1440

1440 TA06

3

4

–

+

20k

1.3M

1M

Low Battery Detect Operates Down to 1.5V