Preliminary Technical Data

AD7357

Rev. PrD | Page 9 of 17

TERMINOLOGY

Integral Nonlinearity (INL)

The maximum deviation from a straight line passing through

the endpoints of the ADC transfer function. The endpoints of

the transfer function are zero scale, 1 LSB below the first code

transition, and full scale, 1 LSB above the last code transition.

Differential Nonlinearity (DNL)

The difference between the measured and the ideal 1 LSB

change between any two adjacent codes in the ADC.

Offset Error

The deviation of the first code transition (00 . . .000) to (00 . . .

Offset Error Match

This is the difference in offset error between the two ADCs.

Gain Error

The deviation of the last code transition (111 . . .110) to (111 . . .

has been adjusted out.

Gain Error Match

The difference in gain error between the two ADCs.

Channel-to-Channel Isolation

Channel-to-channel isolation is a measure of the level of

crosstalk between channels. It is measured by applying a full-

scale sine wave signal to one of the two channels and applying a

50 kHz signal to the other channel. The channel-to-channel

isolation is defined as the ratio of the power of the 50 kHz

signal on the converted channel to the power of the noise signal

on the other channel that appears in the FFT of this channel.

The noise frequency on the unselected channel varies from

Power Supply Rejection Ratio (PSRR)

PSRR is defined as the ratio of the power in the ADC output at

full-scale frequency, f, to the power of a 100 mV p-p sine wave

of the input varies from 1 kHz to 1 MHz.

where:

Pf is the power at frequency f in the ADC output.

Common-Mode Rejection Ratio (CMRR)

CMRR is defined as the ratio of the power in the ADC output at

full-scale frequency, f, to the power of a 100 mV p-p sine wave

where:

Pf is the power at frequency f in the ADC output.

Track-and-Hold Acquisition Time

The track-and-hold amplifier returns to track mode at the end

of conversion. The track-and-hold acquisition time is the time

required for the output of the track-and-hold amplifier to reach

its final value, within ±1/2 LSB, after the end of conversion.

Signal-to-(Noise + Distortion) Ratio (SINAD)

This is the measured ratio of signal-to-noise and distortion at

the output of the ADC. The signal is the rms amplitude of the

fundamental. Noise is the sum of all nonfundamental signals up

dependent on the number of quantization levels in the

digitization process; the more levels, the smaller the

quantization noise.

The theoretical signal-to-noise and distortion ratio for an ideal

N-bit converter with a sine wave input is given by

SINAD = (6.02 N + 1.76) dB

Thus, for a 12-bit converter, this is 74 dB and for a 14 bit

converter, this is 86dB.

Total Harmonic Distortion (THD)

THD is the ratio of the rms sum of harmonics to the

fundamental. For the AD7356, it is defined as

()

1

6

5

4

3

2

V

V

V

V

V

V

THD

2

2

2

2

2

20log

dB

+

+

+

+

−

=

where:

through the sixth harmonics.