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AD7934-6

4-Channel, 625 kSPS, 12-Bit Parallel ADC with a Sequencer

Analog Devices 

TERMINOLOGY

Integral Nonlinearity (INL)

This is 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)

This is the difference between the measured and the ideal 1 LSB

change between any two adjacent codes in the ADC.

Offset Error

This is the deviation of the first code transition (00…000) to

(00…001) from the ideal (that is, AGND + 1 LSB).

Offset Error Match

This is the difference in offset error between any two channels.

Gain Error

This is the deviation of the last code transition (111…110) to

(111…111) from the ideal (that is, VREF – 1 LSB) after the offset

error has been adjusted out.

Gain Error Match

This is the difference in gain error between any two channels.

Zero-Code Error

This applies when using the twos complement output coding

option, in particular to the 2 × VREF input range, with −VREF to

+VREF biased about the VREF point. It is the deviation of the

midscale transition (all 0s to all 1s) from the ideal VIN voltage

(that is, VREF).

Zero-Code Error Match

This is the difference in zero-code error between any two

channels.

Positive Gain Error

This applies when using the twos complement output coding

option, in particular to the 2 × VREF input range, with −VREF to

+VREF biased about the VREF point. It is the deviation of the last

code transition (011…110) to (011…111) from the ideal (that is,

+VREF – 1 LSB) after the zero-code error has been adjusted out.

Positive Gain Error Match

This is the difference in positive gain error between any two

channels.

AD7934-6

Negative Gain Error

This applies when using the twos complement output coding

option, in particular to the 2 × VREF input range, with −VREF to

+VREF biased about the VREF point. It is the deviation of the first

code transition (100 … 000) to (100 … 001) from the ideal

(that is, −VREF + 1 LSB) after the zero-code error has been

adjusted out.

Negative Gain Error Match

This is the difference in negative gain error between any two

channels.

Channel-to-Channel Isolation

This is a measure of the level of crosstalk between channels.

It is measured by applying a full-scale sine wave signal to the

three, nonselected input channels and applying a 50 kHz signal

to the selected channel. The channel-to-channel isolation is

defined as the ratio of the power of the 50 kHz signal on the

selected channel to the power of the noise signal on the unse-

lected channels that appears in the fast Fourier transform (FFT)

of this channel. The noise frequency on the unselected channels

varies from 40 kHz to 740 kHz. The noise amplitude is at

2 × VREF, while the signal amplitude is at 1 × VREF. See Figure 4.

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

applied to the ADC VDD supply of frequency fS. The frequency

of the noise varies from 1 kHz to 1 MHz.

PSRR (dB) = 10 log(Pf/PfS)

where:

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

PfS is the power at frequency fS 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

applied to the common-mode voltage of VIN+ and VIN− of

frequency, fS.

CMRR (dB) = 10 log(Pf/PfS)

where:

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

PfS is the power at frequency fS in the ADC output.

Rev. B | Page 11 of 28

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