AD7666ACP データシートの表示（PDF） - Analog Devices

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AD7666ACP

16-Bit 500 kSPS PulSAR® Unipolar ADC with Reference

Analog Devices 

DEFINITIONS OF SPECIFICATIONS

Integral Nonlinearity Error (INL)

Linearity error refers to the deviation of each individual code

from a line drawn from negative full scale through positive full

scale. The point used as negative full scale occurs ½ LSB before

the first code transition. Positive full scale is defined as a level

1½ LSB beyond the last code transition. The deviation is

measured from the middle of each code to the true straight line.

Differential Nonlinearity Error (DNL)

In an ideal ADC, code transitions are 1 LSB apart. Differential

nonlinearity is the maximum deviation from this ideal value. It

is often specified in terms of resolution for which no missing

codes are guaranteed.

Full-Scale Error

The last transition (from 011…10 to 011…11 in twos

complement coding) should occur for an analog voltage 1½ LSB

below the nominal full scale (2.49994278 V for the 0 V to 2.5 V

range). The full-scale error is the deviation of the actual level of

the last transition from the ideal level.

Unipolar Zero Error

The first transition should occur at a level ½ LSB above analog

ground (19.073 µV for the 0 V to 2.5 V range). Unipolar zero

error is the deviation of the actual transition from that point.

Spurious-Free Dynamic Range (SFDR)

SFDR is the difference, in decibels (dB), between the rms

amplitude of the input signal and the peak spurious signal.

Effective Number Of Bits (ENOB)

ENOB is a measurement of the resolution with a sine wave

input. It is related to S/(N+D) and is expressed in bits by the

following formula:

ENOB = (S/[N+D]dB – 1.76)/6.02

Total Harmonic Distortion (THD)

THD is the ratio of the rms sum of the first five harmonic

components to the rms value of a full-scale input signal, and is

expressed in decibels.

Signal-to-Noise Ratio (SNR)

SNR is the ratio of the rms value of the actual input signal to the

rms sum of all other spectral components below the Nyquist

frequency, excluding harmonics and dc. The value for SNR is

expressed in decibels.

Signal-to-(Noise + Distortion) Ratio (S/[N+D])

S/(N+D) is the ratio of the rms value of the actual input signal

to the rms sum of all other spectral components below the

Nyquist frequency, including harmonics but excluding dc. The

value for S/(N+D) is expressed in decibels.

AD7666

Aperture Delay

Aperture delay is a measure of the acquisition performance and

is measured from the falling edge of the CNVST input to when

the input signal is held for a conversion.

Transient Response

Transient response is the time required for the AD7666 to

achieve its rated accuracy after a full-scale step function is

applied to its input.

Reference Voltage Temperature Coefficient

Reference voltage temperature coefficient is derived from the

maximum and minimum reference output voltage (VREF)

measured at TMIN, T(25°C), and TMAX. It is expressed in ppm/°C

using the following equation:

TCVREF

(

ppm

/

°C)

=

VREF ( Max)

VREF (25°C) ×

– VREF

(TMAX

( Min)

– TMIN

)

× 10 6

where:

VREF(Max) = Maximum VREF at TMIN, T(25°C), or TMAX

VREF(Min) = Minimum VREF at TMIN, T(25°C), or TMAX

VREF(25°C) = VREF at +25°C

TMAX = +85°C

TMIN = –40°C

Thermal Hysteresis

Thermal hysteresis is defined as the absolute maximum change

of reference output voltage after the device is cycled through

temperature from either

T_HYS+ = +25°C to TMAX to +25°C

T_HYS– = +25°C to TMIN to +25°C

It is expressed in ppm using the following equation:

VHYS ( ppm) =

VREF (25°C) − VREF (T _ HYS)

VREF (25°C)

× 106

where:

VREF(25°C) = VREF at 25°C

VREF(T_HYS) = Maximum change of VREF at T_HYS+ or

T_HYS–.

Rev. 0 | Page 11 of 28

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