SC70, 1.6V, Nanopower, Beyond-the-Rails

Comparators With/Without Reference

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11

THRESHOLDS

OUT

IN+

IN-

HYSTERESIS

BAND

Figure 2. Threshold Hysteresis Band

MAX9117

MAX9119

OUT

R3

R1

R2

Figure 3. MAX9117/MAX9119 Additional Hysteresis

are 1.2M

Ω and 3.8MΩ. Choose a 1.2MΩ standard

value for R3.

example, choose 50mV.

3) Calculate R1 according to the following equation:

For this example, insert the values:

R1 = 1.2M

Ω (50mV / 5V) = 12kΩ

the comparator switches its output from low to high

choose 3V.

5) Calculate R2 as follows:

Ω) - (1 / 12kΩ) -

(1 / 1.2M

Ω)] = 8.655kΩ

For this example, choose an 8.66k

Ω standard 1% value.

6) Verify the trip voltages and hysteresis as follows:

+ (1 / R3)] = 3V

Additional Hysteresis (MAX9118/MAX9120)

The MAX9118/MAX9120 have a 4mV internal hysteresis

band. They have open-drain outputs and require an

external pullup resistor (Figure 4). Additional hysteresis

can be generated using positive feedback, but the for-

mulas differ slightly from those of the MAX9117/

MAX9119. Use the following procedure to calculate

resistor values.

the two resulting resistor values.

3) Calculate R1 according to the following equation:

age at which the comparator switches its output

5) Calculate R2 as follows:

6) Verify the trip voltages and hysteresis as follows:

V

falling

VV

R

RR

RR

R

RR

V

IN

THF

REF

CC

:

=×

+

+

+

⎛

⎝⎜

⎞

⎠⎟

+

×

−

1

1

1

1

2

1

34

1

34

Vri

g

V

V

R

RR

R

IN

THR

REF

sin :

=×

+

+

⎛

⎝⎜

⎞

⎠⎟

1

1

1

1

2

1

3

R

V

VR

R

R

THR

REF

21

1

1

1

1

3

=

×

⎛

⎝⎜

⎞

⎠⎟

⎡

⎣

⎢

⎢

⎤

⎦

⎥

⎥

−−

/