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Max1421, Dynamic parameter definitions – Rainbow Electronics MAX1421 User Manual

Page 14

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MAX1421

error specification of less than 1LSB guarantees no
missing codes.

Dynamic Parameter Definitions

Aperture Jitter

Figure 10 depicts the aperture jitter (t

AJ

), which is the

sample-to-sample variation in the aperture delay.

Aperture Delay

Aperture delay (t

AD

) is the time defined between the

falling edge of the sampling clock and the instant when
an actual sample is taken (Figure 10).

Signal-to-Noise Ratio (SNR)

For a waveform perfectly reconstructed from digital
samples, the theoretical maximum SNR is the ratio of

the full-scale analog input (RMS value) to the RMS
quantization error (residual error). The ideal theoretical
minimum analog-to-digital noise is caused by quantiza-
tion error only and results directly from the ADCs reso-
lution (N-bits):

SNR

(MAX)

= (6.02

N + 1.76)dB

In reality, there are other noise sources besides quanti-
zation noise e.g., thermal noise, reference noise, clock
jitter, etc. SNR is computed by taking the ratio of the
RMS signal to the RMS noise, which includes all spec-
tral components minus the fundamental, the first four
harmonics, and the DC offset.

12-Bit, 40Msps, +3.3V, Low-Power ADC
with Internal Reference

14

______________________________________________________________________________________

INPUT

300

-5V

+5V

0.1

µF

0.1

µF

0.1

µF

0.1

µF

C

IN

*

22pF

1nF

0.22

µF

44pF*

R

ISO

50

R

ISO

50

-5V

600

300

300

INP

INN

LOWPASS FILTER

CML

600

+5V

-5V

0.1

µF

300

300

600

300

0.1

µF

0.1

µF

0.1

µF

+5V

0.1

µF

300

MAX4108

MAX1421

MAX4108

MAX4108

LOWPASS FILTER

*TWO C

IN

(22pF) CAPS MAY BE REPLACED BY

ONE 44pF CAP, TO IMPROVE PERFORMANCE.

C

IN

*

22pF

Figure 7. Typical Application Circuit for Single-Ended to Differential Conversion