9

LTC1443/LTC1444/LTC1445

Level Detector

The LTC1444 is ideal for use as a multisupply micropower

level detector as shown in Figure 5.

R1 and R2 form a voltage divider from V1 to the noninverting

comparator A input. R6 and R7 are used to divide down V2,

while R8 is the output pull-up resistor for the comparator

outputs. R3 and R4 set the hysteresis voltage and R5 and C1

bypass the reference output. The following design procedure

can be used to select the component values:

1. Choose the V1 voltage trip level, in this example 4.65V.

2. Calculate the required resistive divider ratio.

Ratio = 1.221V/4.65V = 0.263

3. Choose the required hysteresis voltage band at the input,

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.

RR

V

V

V

RM

V

V

mV

RM

IN

REF

HB

21

2

1

21 21

465

1 221

15

2

1

23 40

=

()

+

−





















=

()

+

−





















=

.

.

.

.

Using the same equations, R6 and R7 are 1.82M and 1.21M

respectfully to set the trip level at 3V for V2.

5

OUT B

OUT A

R3

15k, 1%

R5

430

Ω

5%

R4

2.4M

1%

C1

1.0

µF

HYST

REF

4

14

8

7

6

–

+

LTC1443/44/45 • F05

1/2LTC1444

3

9

2

1

R1

1.21M

1%

R2

3.40M

1%

V1

R7

1.21M

1%

R6

1.82M

1%

V2

R8

2M

1%

5V

–

+

Figure 5. Glitch-Free Level Detector with Hysteresis

APPLICATIO S I FOR ATIO