MAX1215(2005) 查看數據表（PDF） - Maxim Integrated

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MAX1215
(Rev.:2005)

1.8V, 12-Bit, 250Msps ADC for Broadband Applications

Maxim Integrated 

1.8V, 12-Bit, 250Msps ADC for

Broadband Applications

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 MAX1215 are mea-

sured using the histogram method with a 10MHz input

frequency.

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. The

MAX1215’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 (tAJ), which is the

sample-to-sample variation in the aperture delay.

Aperture Delay

Aperture delay (tAD) is the time defined between the

rising edge of the sampling clock and the instant when

an actual sample is taken (Figure 11).

CLKP

CLKN

ANALOG

INPUT

tAD

tAJ

SAMPLED

DATA (T/H)

T/H TRACK

HOLD

TRACK

Figure 11. Aperture Jitter/Delay Specifications

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[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

signal-to-noise ratio 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 the case of the MAX1215,

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.

Intermodulation Distortion (IMD)

IMD is the ratio of the RMS sum of the intermodulation

products to the RMS sum of the two fundamental input

tones. This is expressed as:



IMD = 20 × log



VIM12

+

VIM22

+ ......+

VIM32

+

VIMn 2





V12 + V22





The fundamental input tone amplitudes (V1 and V2) are at

-7dBFS. The intermodulation products are the amplitudes

of the output spectrum at the following frequencies:

• Second-order intermodulation products: fIN1 + fIN2,

fIN2 - fIN1

• Third-order intermodulation products: 2 x fIN1 - fIN2,

2 x fIN2 - fIN1, 2 x fIN1 + fIN2, 2 x fIN2 + fIN1

• Fourth-order intermodulation products: 3 x fIN1 - fIN2,

3 x fIN2 - fIN1, 3 x fIN1 + fIN2, 3 x fIN2 + fIN1

• Fifth-order intermodulation products: 3 x fIN1 - 2 x fIN2,

3 x fIN2-2 x fIN1, 3 x fIN1+2 x fIN2, 3 x fIN2 + 2 x fIN1

Full-Power Bandwidth

A large -1dBFS analog input signal is applied to an

ADC and the input frequency is swept up to the point

where the amplitude of the digitized conversion result

has decreased by 3dB. The -3dB point is defined as

the full-power input bandwidth frequency of the ADC.

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