6) Verify the trip voltages and hysteresis as follows:

times R1 divided by the parallel combination of R1,

R2:

and R3.

Additional Hysteresis

(MAX9016/MAX9018/MAX9020)

(Open-Drain Outputs)

The MAX9016/MAX9018/MAX9020 feature a built-in 4mV

hysteresis band. These devices have open-drain outputs

and require an external pullup resistor (Figure 3).

Additional hysteresis can be generated using positive

feedback, but the formulas differ slightly from those of

the MAX9015/MAX9017/MAX9019. Use the following

procedure to calculate resistor values:

1) Select R3. Input bias current at IN_+ is less than

2nA, so the current through R3 should be at least

0.2µA to minimize errors caused by input bias cur-

rent. The current through R3 at the trip point is

put states in solving for R3 yields two formulas: R3

smaller of the two resulting resistor values. For

R4 = 1M

Ω, then the two resistor values are 6.2MΩ

and 18M

Ω. Choose a 6.2MΩ standard value for R3.

3) Calculate R1 according to the following equation.

For this example, insert the values:

threshold voltage at which the comparator switches

trip point. For this example, choose 3V:

5) Calculate R2 as follows:

For this example, choose a 49.9k

Ω standard value.

6) Verify the trip voltages and hysteresis as follows:

V

falling V

V

x R

RR

R

R

RR

xV

V

IN

THF

REF

CC

:

.

=









+ 







+ 















−

+

=

1

1

1

1

2

1

3

1

34

2 993

Vri

g V

V

x R

RR

R

V

IN

THR

REF

sin :

.

=









+ 







+ 















=

1

1

1

1

2

1

3

3 043

R

V

Vx

k

k

M

k

2

1

30

124

72

1

72

1

62

51 1

=

Ω









−

Ω









−

Ω

























=Ω

.

..

.

R

V

Vx R

R

R

THR

REF

2

1

1

1

1

1

3

=









− 







− 























VV

V

V

THR

REF

HB

CC

>+









1

RM

M

mV

V

k

16 2

1

50

5

72

=Ω +

Ω 







=Ω

(.

)

RR

R

V

V

HB

CC

13

4

=+









()

VV

Rx V

R

THF

THR

CC

=− 







1

3

VV

x R

RR

R

THR

REF

=









+ 







+ 



















1

1

1

1

2

1

3

SOT23, Dual, Precision, 1.8V, Nanopower

Comparators With/Without Reference

______________________________________________________________________________________

13

OUT

R3

R2

R1

R4

MAX9016

MAX9018

MAX9020

Figure 3. MAX9016/MAX9018/MAX9020 Additional Hysteresis