(1

Ω to 5Ω), a ferrite bead, or a direct short.

Alternatively, all ground pins could share the same

ground plane, if the ground plane is sufficiently isolated

from any noisy, digital systems ground plane (e.g.

downstream output buffer or DSP ground plane). Route

high-speed digital signal traces away from the sensitive

analog traces of either channel. Make sure to isolate

the analog input lines to each respective converter to

minimize channel-to-channel crosstalk. Keep all signal

lines short and free of 90 degree turns.

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 endpoints of the transfer function, once

offset and gain errors have been nullified. The static lin-

earity parameters for the MAX1183 are measured using

the best straight-line fit method.

Differential Nonlinearity (DNL)

Differential nonlinearity is the difference between an

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

error specification of less than 1LSB guarantees no

missing codes and a monotonic transfer function.

Dynamic Parameter

Definitions

Aperture Jitter

sample-to-sample variation in the aperture delay.

Aperture Delay

falling edge of the sampling clock and the instant when

an actual sample is taken (Figure 9).

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 quanti-

zation error (residual error). The ideal, theoretical mini-

mum analog-to-digital noise is caused by quantization

error only and results directly from the ADCs resolution

(N-Bits):

In reality, there are other noise sources besides quanti-

zation noise: thermal noise, reference noise, clock jitter,

etc. SNR is computed by taking the ratio of the rms sig-

nal to the rms noise, which includes all spectral compo-

Dual 10-Bit, 40Msps, +3V, Low-Power ADC with

Internal Reference and Parallel Outputs

16

______________________________________________________________________________________

0

°

90

°

÷8

DOWNCONVERTER

MAX2451

INA+

MAX1183

INA-

INB+

INB-

DSP

POST-

PROCESSING

Figure 8. Typical QAM Application, Using the MAX1183

HOLD

ANALOG

INPUT

SAMPLED

DATA (T/H)

T/H

TRACK

TRACK

CLK

Figure 9. T/H Aperture Timing