Figure 6: Interfacing the CLC503 with the CLC949

Extended Use Considerations

Designed to drive the CLC949, the CLC503 can be

used with other analog-to-digital converters. The user

will want to consider the following parameters of the

device that the CLC503 will drive.

s

Input impedance of the A/D. Refer to Figure 5

for the Gain vs. Resistive Load. The CLC503

operates best when driving resistive loads

greater than 10k

Ω and capacitive loads of less

than 10pF.

s

Resistive loading will affect the gain and common

mode offset. The gain setting resistors are

fixed internally. The voltage gain equation is:

tolerance on the 500

Ω is ±20%.

s

Capacitive loading will affect the settling time.

The settling time equation is:

to the

Settling Time vs. Capacitive Load plot in the

Typical Performance Characteristics section.

s

Other considerations

s

Output signal swing must be within the

specified output range.

s

Common mode range must meet the

specified common mode range.

s

operating range.

AA

500

|| R

500

vv

L

new

old

=









Ω

Ω

t

RCln

100%

%settling

settle

s

L

=⋅

⋅









CLC503

CLC949

74AC04

Power Down

ADC Clock

GND

BIASC

CLK

GND

-5V

0.1

µF

0.1

µF

0.1

µF

12b/20MSPS ADC

6.8

µF

+5V

0.1

µF

6.8

µF

http://www.national.com

6

Lit #150503-002

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sustain life, and whose failure to perform, when properly used in accordance with instructions for use provided in the labeling, can

be reasonably expected to result in a significant injury to the user.

2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to

cause the failure of the life support device or system, or to affect its safety or effectiveness.

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