ADSP-BF504 datasheet(60/80 Pages) AD

60 / 80 page

Rev. PrC

Page 60 of 80

January 2010

ADSP-BF504/F,ADSP-BF506F

Preliminary Technical Data

ADC — TERMINOLOGY

Differential Nonlinearity (DNL)

Differential nonlinearity is the difference between the mea-

sured and the ideal 1 LSB change between any two adjacent

codes in the ADC.

Integral Nonlinearity (INL)

Integral nonlinearity is the maximum deviation from a

straight line passing through the endpoints of the ADC trans-

fer function. The endpoints of the transfer function are zero

scale with a single (1) LSB point below the first code transi-

tion, and full scale with a 1 LSB point above the last code

transition.

Offset Error

Offset error applies to straight binary output coding. It is the

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

(00 . . . 001) from the ideal (AGND + 1 LSB).

Offset Error Match

Offset error match is the difference in offset error across all 12

channels.

Gain Error

Gain error applies to straight binary output coding. It is the

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

(111 . . . 111) from the ideal (VREF 1 LSB) after the offset error

is adjusted out. Gain error does not include reference error.

Gain Error Match

Gain error match is the difference in gain error across all 12

channels.

Positive Gain Error

This applies when using twos complement output coding

with, for example, the 2 × VREF input range as –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 (+VREF

1 LSB) after the zero code error is adjusted out.

Positive Gain Error Match

This is the difference in positive gain error across all 12

channels.

Zero Code Error

Zero code error applies when using twos complement output

coding with, for example, the 2 × VREF input range as –VREF to

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

mid-scale transition (all 0s to all 1s) from the ideal VIN voltage

(VREF).

Zero Code Error Match

Zero code error match refers to the difference in zero code

error across all 12 channels.

Negative Gain Error

This applies when using twos complement output coding

option, in particular the 2 × VREF input range as –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 is adjusted

out.

Negative Gain Error Match

This is the difference in negative gain error across all 12

channels.

Track-and-Hold Acquisition Time

The track-and-hold amplifier returns to track mode after the

end of conversion. 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 ratio is the measured ratio of signal-to-(noise + distor-

tion) at the output of the ADC. The signal is the rms

amplitude of the fundamental. Noise is the sum of all non-

fundamental signals up to half the sampling frequency (fS/2),

excluding dc. The ratio is dependent on the number of quan-

tization levels in the digitalization process; the more levels,

the smaller the quantization noise. The theoretical signal-to-

(noise + distortion) ratio for an ideal N-bit converter with a

sine wave input is given by

Signal-to-(Noise + Distortion) = (6.02N + 1.76) dB

Therefore, for a 12-bit converter, theoretical SINAD is 74 dB.

Total Harmonic Distortion (THD)

Total harmonic distortion is the ratio of the rms sum of har-

monics to the fundamental. For the ADC, it is defined as

where:

V1 is the rms amplitude of the fundamental.

V2, V3, V4, V5, and V6 are the rms amplitudes of the second

through the sixth harmonics.

Effective Number of Bits (ENOB)

This is a figure of merit which characterizes the dynamic per-

formance of the ADC at a specified input frequency and

sampling rate. ENOB is expressed in bits. For a full scale sinu-

soidal input, ENOB is defined as:

ENOB = (SINAD – 1.76)/6.02.

Peak Harmonic or Spurious Noise (SFDR)

Peak harmonic, or spurious noise, is defined as the ratio of

the rms value of the next largest component in the ADC out-

put spectrum (up to fS/2, excluding dc) to the rms value of the

fundamental. Normally, the value of this specification is

determined by the largest harmonic in the spectrum, but for

ADCs where the harmonics are buried in the noise floor, it is

a noise peak.

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 (2 × VREF when VDD = 5 V, VREF when VDD = 3 V),

10 kHz sine wave signal to all un-selected input channels and

log

)

(

THD

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