MCP33131 datasheet(41/54 Pages) MICROCHIP

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DS20006122A-page 41

MCP33131/MCP33121/MCP33111-XX

8.0

TERMINOLOGY

Analog Input Bandwidth (Full-Power

Bandwidth)

The analog input frequency at which the spectral power

of the fundamental frequency (as determined by FFT

analysis) is reduced by 3 dB.

Aperture Delay or Sampling Delay

This is the time delay between the rising edge of the

CNVST input and when the input signal is held for a

conversion.

Differential Nonlinearity

(DNL, No Missing Codes)

An ideal ADC exhibits code transitions that are exactly

1 LSB apart. DNL is the deviation from this ideal value.

No missing codes to 16-bit resolution indicates that all

65,536 codes (16,384 codes for 14-bit, 4096 codes for

12-bit) must be present over all the operating

conditions.

Integral Nonlinearity (INL)

INL is the maximum deviation of each individual code

from an ideal straight line drawn from negative full

scale through positive full scale.

Signal-to-Noise Ratio (SNR)

SNR is the ratio of the power of the fundamental (PS) to

the noise floor power (PN), below the Nyquist frequency

and excluding the power at DC and the first nine

harmonics.

EQUATION 8-1:

SNR is either given in units of dBc (dB to carrier), when

the absolute power of the fundamental is used as the

reference, or dBFS (dB to full-scale), when the power

of the fundamental is extrapolated to the converter

full-scale range.

Signal-to-Noise and Distortion (SINAD)

SINAD is the ratio of the power of the fundamental (PS)

to the power of all the other spectral components

including noise (PN) and distortion (PD) below the

Nyquist frequency, but excluding DC:

EQUATION 8-2:

SINAD is either given in units of dBc (dB to carrier),

when the absolute power of the fundamental is used as

the reference, or dBFS (dB to full-scale), when the

power of the fundamental is extrapolated to the

converter full-scale range.

Effective Number of Bits (ENOB)

The effective number of bits for a sine wave input at a

given input frequency can be calculated directly from its

measured SINAD using the following formula:

EQUATION 8-3:

Gain Error

Gain error is the deviation of the ADC’s actual input

full-scale range from its ideal value. The gain error is

given as a percentage of the ideal input full-scale

range. Gain error is usually expressed in LSB or as a

percentage of full-scale range (%FSR).

Offset Error

Offset error is the difference between the ideal voltage

(0V + 0.5 LSB) that produces the first code transition

(“000... 000” to “000... 001”) and the actual voltage pro-

ducing that code.

Temperature Drift

The temperature drift for offset error and gain error

specifies the maximum change from the initial (+25°C)

value to the value at across the TMIN to TMAX range.

The value is normalized by the reference voltage and

expressed in

V/oC or ppm/oC.

Maximum Conversion Rate

The maximum clock rate at which parametric testing is

performed.

Spurious-Free Dynamic Range (SFDR)

SFDR is the ratio of the power of the fundamental to the

highest other spectral component (either spur or

harmonic). SFDR is typically given in units of dBc (dB

to carrier) or dBFS.

SNR

-------







log

SINAD

PD PN

----------------------







log

–

=10

SNR

-----------

–

THD

------------

–

log

ENOB

SINAD 1.76

–

6.02

----------------------------------

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