LTC1443/LTC1444/LTC1445

10

144345fe

applicaTions inForMaTion

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 non-

inverting 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.

5

OUT B

OUT A

R3

15k, 1%

R5

430

5%

R4

2.4M

1%

C1

1.0µF

HYST

REF

4

14

8

7

6

–

+

144345 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

–

+

1.2V

+–

Figure 5. Glitch-Free Level Detector with Hysteresis

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. Choosetherequiredhysteresisvoltagebandattheinput,

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

R4 = 2.4M

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

R2

= R1

( )

2

− 1





















R2

= 1.21M

(

)

4.65V

1.221V

+ 15mV

2

− 1





















R2

= 3.40M

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

1.21M, respectively, to set the trip level at 3V for V2.