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input bias current in order to minimize errors. The calculation

of the resistor values as follows:

order to minimize the propagation delay time.

greater than the input bias current as follows:

The above two methods will generate hysteresis of up to a

may be required.

Power Dissipation

When switching at high speeds, the comparator's drive

capability is limited by the rise in junction temperature

caused by the internal power dissipation. For reliable

operation, the junction temperature must be kept below

An approximate equation for the device power dissipation is

as follows. Assume the power dissipation in the load is very

small:

where:

N is the number of comparators in the package

Please refer to the performance curve to choose the input

driving frequency. Having obtained the power dissipation, the

maximum junction temperature can be determined as

follows:

where:

Threshold Detector

The inverting input is connected to a reference voltage and

the non-inverting input is connected to the input. As the input

changes state. The non-inverting and inverting inputs may

be reversed.

Crystal Oscillator

A simple crystal oscillator using one comparator of an

appropriate DC average voltage based on the output. The

crystal's path provides resonant positive feedback and stable

oscillation occurs. Although the EL5485 and EL5486 will give

the correct logic output when an input is outside the common

mode range, additional delays may occur when it is so

operated. Therefore, the DC bias voltages at the inputs are

set about 500mV below the center of the common mode

range and the 200

Ω resistor attenuates the feedback to the

non-inverting input. The circuit will operate with most AT-cut

crystal from 1MHz to 8MHz over a 2V to 7V supply range.

The output duty cycle for this circuit is roughly 50% at 5V

R

3

V

(

SD

0.8

)

R

1

V

H

--------

×

–

=

I

0.5V

SD

V

REF

–

R

3

------------------------------------------

=

P

DISS

V

S

I

S

V

SD

I

×

+

×

N

×

(

=

T

JMAX

T

MAX

Θ

JA

P

DISS

×

+

=

+

-

+

-

200

Ω

5V

1MHz to

8MHz

2k

Ω

0.01µF

5k

Ω

1.5k

Ω

2k

Ω

EL5485, EL5486