LTC6702

7

6702fa

APPLICATIONS INFORMATION

The LTC6702 device is a fast (500ns delay), low power,

low voltage (1.7V to 5.5V supply) general purpose dual

comparator. It provides rail-to-rail outputs able to interface

to TTL/CMOS, draws low supply currents (30μA/compara-

tor), and has internal hysteresis (approximately 4mV).

Hysteresis

Each comparator has built-in hysteresis to simplify designs,

to insure stable operation in the presence of noise at the

inputs, and to reject supply rail noise. The reference voltage

applied to the input is not the exact switching threshold

value due to the built-in hysteresis. Actual output switching

typically occurs within ±2.2mV of the reference voltage,

plus or minus the input offset voltage. External positive

feedback circuitry can be employed to increase effective

hysteresis if desired, as shown in Figure 1. This circuitry

will provide an apparent effect on both the rising and fall-

ing input thresholds (the actual internal trip points remain

unaffected). If an inverting configuration with hysteresis is

Unused Inputs

Any unused inputs should be connected in a way that fixes

the output logic state high or low. One easy way to do this

Input Protection

External input protection circuitry is only needed if currents

would otherwise exceed the absolute maximum rating.

Inputs driven further negative than 100mV below ground

will not cause damage provided the current is limited to

10mA. ESD protection diodes are provided to prevent

damage during handling.

Comparator Input

The allowable input voltage ranges from 100mV below GND

to within 1.2V of the positive supply. The input may be

forced below ground without causing an improper output,

though some additional input current will begin to flow

from the ESD input protection diode. The inputs can reach

causing additional input current or damage to the part.

As long as one input is within the allowable input voltage

range, the LTC6702 will continue to function normally.

Comparator Output

The comparator output is a push-pull CMOS stage

of ground, over temperature when sourcing or sinking

15mA. No external pull-up/down resistor is required. To

Figure 1. Additional Hysteresis Circuit for Noninverting Configuration

Additional Hystersis

R

R

V

Trip Voltages

V

IN

=

+

1

3

•

:

(()

()

••

LH

REF

IN H

L

R

VR

RR

R

VV

→

→

=+

+

⎛

⎝⎜

⎞

⎠⎟

=

1

1

1

1

2

1

3

E

EF

R

RR

R

R

R

V

Examp

••

•

1

1

1

1

2

1

3

1

3

++

⎛

⎝⎜

⎞

⎠⎟

−

⎛

⎝⎜

⎞

⎠⎟

+

lle Additional Hysteresis

mV V

V

Rk

R

:,

==

=

+

50

5

110

2

==

=

=→ =

249

31

05

0525

k

M

FOR V

V V

L

H

V

V

REF

IN

IN

R

.:

(

)

.

(H

HL

V

→=

).

0 475

–

+

1/2 LTC6702

R2

R3

6702 F01

R1