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MAX1121

Static Parameter Definitions

Integral Nonlinearity (INL)

Integral nonlinearity is the deviation of the values on an

actual transfer function from a straight line. This straight

line can be either a best straight-line fit or a line drawn

between the end points of the transfer function, once

offset and gain errors have been nullified. However, the

static linearity parameters for the MAX1121 are mea-

sured using the histogram method with an input fre-

quency of 10MHz.

Differential Nonlinearly (DNL)

Differential nonlinearity is the difference between an

actual step width and the ideal value of 1 LSB. A DNL

error specification of less than 1 LSB guarantees no

missing codes and a monotonic transfer function. The

MAX1121’s DNL specification is measured with the his-

togram method based on a 10MHz input tone.

Dynamic Parameter Definitions

Aperture Jitter

Figure 11 depicts the aperture jitter (t

), which is the

sample-to-sample variation in the aperture delay.

Aperture Delay

Aperture delay (t

) is the time defined between the

falling edge of the sampling clock and the instant when

an actual sample is taken (Figure 11).

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 ADC’s reso-

lution (N bits):

SNR

dB[max]

= 6.02

x N + 1.76

In reality, other noise sources such as thermal noise,

clock jitter, signal phase noise, and transfer function

nonlinearities are also contributing to the SNR calcula-

tion and should be considered when determining the

SNR in ADC.

Signal-to-Noise Plus Distortion (SINAD)

SINAD is computed by taking the ratio of the RMS sig-

nal to all spectral components excluding the fundamen-

tal and the DC offset. In case of the MAX1121, SINAD

is computed from a curve fit.

Spurious-Free Dynamic Range (SFDR)

SFDR is the ratio of RMS amplitude of the carrier fre-

quency (maximum signal component) to the RMS value

of the next-largest noise or harmonic distortion compo-

nent. SFDR is usually measured in dBc with respect to

the carrier frequency amplitude or in dBFS with respect

to the ADC’s full-scale range.

Two-Tone Intermodulation Distortion (IMD)

The two-tone IMD is the ratio expressed in decibels of

either input tone to the worst 3rd-order (or higher) inter-

modulation products. The individual input tone levels

are at -7dB full scale.

1.8V, 8-Bit, 250Msps Analog-to-Digital Converter

with LVDS Outputs for Wideband Applications

16 ______________________________________________________________________________________

HOLD

ANALOG

INPUT

SAMPLED

DATA (T/H)

T/H

TRACK TRACK

CLKN

CLKP

Figure 11. Aperture Jitter/Delay Specifications

PART

RESOLUTION

(Bits)

SPEED GRADE

(Msps)

MAX1122 10 170

MAX1123 10 210

MAX1124 10 250

Pin-Compatible Higher

Resolution Versions

1 2 ... 11 12 13 14 15 16 17

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