ADC的各项参数定义：

Parameter Definitions
Integral Nonlinearity (INL)
Integral nonlinearity is the deviation of the values on an
actual transfer function from a straight line. For the
MAX1209, this straight line is between the end points of
the transfer function, once offset and gain errors have
been nullified. INL deviations are measured at every
step of the transfer function and the worst-case deviation
is reported in the Electrical Characteristics table.

Differential Nonlinearity (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. For
the MAX1209, DNL deviations are measured at every
step of the transfer function and the worst-case deviation
is reported in the Electrical Characteristics table.

Offset Error
Offset error is a figure of merit that indicates how well
the actual transfer function matches the ideal transfer
function at a single point. Ideally the midscale
MAX1209 transition occurs at 0.5 LSB above midscale.
The offset error is the amount of deviation between the
measured midscale transition point and the ideal midscale
transition point.

Gain Error
Gain error is a figure of merit that indicates how well the
slope of the actual transfer function matches the slope
of the ideal transfer function. The slope of the actual
transfer function is measured between two data points:
positive full scale and negative full scale. Ideally, the
positive full-scale MAX1209 transition occurs at 1.5
LSBs below positive full scale, and the negative fullscale
transition occurs at 0.5 LSB above negative full
scale. The gain error is the difference of the measured
transition points minus the difference of the ideal transition
points.

Small-Signal Noise Floor (SSNF)
Small-signal noise floor is the integrated noise and distortion
power in the Nyquist band for small-signal
inputs. The DC offset is excluded from this noise calculation.
For this converter, a small signal is defined as a
single tone with an amplitude less than -35dBFS. This
parameter captures the thermal and quantization noise
characteristics of the converter and can be used to
help calculate the overall noise figure of a receive
channel. Go to www.maxim-ic.com for application
notes on thermal + quantization noise floor.

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 quantization
error only and results directly from the ADC’s resolution
(N bits):
SNR[max] = 6.02 × N + 1.76
In reality, there are other noise sources besides quantization
noise: thermal noise, reference noise, clock jitter,etc.
SNR is computed by taking the ratio of the RMS
signal to the RMS noise. RMS noise includes all spectral
components to the Nyquist frequency excluding the
fundamental, the first six harmonics (HD2–HD7), and
the DC offset.

Signal-to-Noise Plus Distortion (SINAD)
SINAD is computed by taking the ratio of the RMS signal
to the RMS noise plus distortion. RMS noise plus distortion
includes all spectral components to the Nyquist frequency
excluding the fundamental and the DC offset.

Effective Number of Bits (ENOB)
ENOB specifies the dynamic performance of an ADC at
a specific input frequency and sampling rate. An ideal
ADC’s error consists of quantization noise only. ENOB for
a full-scale sinusoidal input waveform. is computed from:
（SINAD - 1.76）/ 6.02

Single-Tone Spurious-Free Dynamic Range
(SFDR)
SFDR is the ratio expressed in decibels of the RMS
amplitude of the fundamental (maximum signal component)
to the RMS amplitude of the next-largest spurious
component, excluding DC offset.

Total Harmonic Distortion (THD)
THD is the ratio of the RMS sum of the first six harmonics
of the input signal to the fundamental itself. This is
expressed as:
where V1 is the fundamental amplitude, and V2 through
V7 are the amplitudes of the 2nd- through 7th-order
harmonics (HD2-HD7).


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:
The fundamental input tone amplitudes (V1 and V2) are
at -7dBFS. Fourteen intermodulation products (VIM_)
are used in the MAX1209 IMD calculation. The intermodulation
products are the amplitudes of the output
spectrum at the following frequencies, where fIN1 and
fIN2 are the fundamental input tone 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


Third-Order Intermodulation (IM3)
IM3 is the total power of the third-order intermodulation
products to the Nyquist frequency relative to the total
input power of the two input tones fIN1 and fIN2. The
individual input tone levels are at -7dBFS. The thirdorder
intermodulation products are 2 x fIN1 - fIN2, 2 x
fIN2 - fIN1, 2 x fIN1 + fIN2, 2 x fIN2 + fIN1.

Two-Tone Spurious-Free Dynamic Range
(SFDRTT)
SFDRTT represents the ratio, expressed in decibels, of
the RMS amplitude of either input tone to the RMS
amplitude of the next-largest spurious component in
the spectrum, excluding DC offset. This spurious component
can occur anywhere in the spectrum up to
Nyquist and is usually an intermodulation product or a
harmonic.

Full-Power Bandwidth
A large -0.5dBFS 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. This point is defined as fullpower
input bandwidth frequency.
In practical laboratory measurements, full-power bandwidth
is limited by the analog input circuitry and not the
ADC itself. For the MAX1209, the full-power bandwidth is
tested using the MAX1211 evaluation kit input circuitry.

Aperture Delay
The MAX1209 samples data on the falling edge of its
sampling clock. In actuality, there is a small delay
between the falling edge of the sampling clock and the
actual sampling instant. Aperture delay (tAD) is the time
defined between the falling edge of the sampling clock
and the instant when an actual sample is taken (Figure 4).

Aperture Jitter
Figure 4 depicts the aperture jitter (tAJ), which is the
sample-to-sample variation in the aperture delay.

Output Noise (nOUT)
The output noise (nOUT) parameter is similar to the thermal
+ quantization noise parameter and is an indication
of the ADC’s overall noise performance.
No fundamental input tone is used to test for nOUT; INP,
INN, and COM are connected together and 1024k data
points collected. nOUT is computed by taking the RMS
value of the collected data points.

Overdrive Recovery Time
Overdrive recovery time is the time required for the
ADC to recover from an input transient that exceeds the
full-scale limits. The MAX1209 specifies overdrive
recovery time using an input transient that exceeds the
full-scale limits by ±10%.