PCM1608YSLASH2K datasheet(28/29 Pages) TI

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PCM1608

SBAS164A

KEY PERFORMANCE PARAMETERS

AND MEASUREMENT

This section provides information on how to measure key

dynamic performance parameters for the PCM1608. In all

cases, an Audio Precision System Two Cascade or equiva-

lent audio measurement system is utilized to perform the

testing.

TOTAL HARMONIC DISTORTION + NOISE

Total Harmonic Distortion + Noise (THD+N) is a significant

figure of merit for audio DACs, since it takes into account

both harmonic distortion and all noise sources within a

specified measurement bandwidth. The true rms value of the

distortion and noise is referred to as THD+N. The test setup

for THD+N testing is shown in Figure 21.

For the PCM1608 DACs, THD+N is measured with a full-

scale, 1kHz digital sine wave as the test stimulus at the input

of the DAC. The digital generator is set to a 24-bit audio

word length and a sampling frequency of 44.1kHz, or 96kHz.

The digital generator output is taken from the unbalanced

S/PDIF connector of the measurement system. The

S/PDIF data is transmitted via coaxial cable to the digital

audio receiver on the DEM-DAI1602 demo board. The

receiver is then configured to output 24-bit data in either I2S

or left-justified data format. The DAC audio interface format

is programmed to match the receiver output format. The

analog output is then taken from the DAC post filter and

connected to the analog analyzer input of the measurement

system. The analog input is band-limited, using filters resi-

dent in the analyzer. The resulting THD+N is measured by

the analyzer and displayed by the measurement system.

FIGURE 21. Test Setup for THD+N Measurements.

S/PDIF

Receiver

Evaluation Board

–3dB = 54kHz

PCM1608

DEM-DAI1608

2nd-Order

Low-Pass

Filter

Notch Filter

Band Limit

HPF = 22Hz(1)

LPF = 30kHz(1)

C = 1kHz

rms Mode

100% Full-Scale

24-Bit, 1kHz

Sine Wave

S/PDIF

Output

Option = 20kHz Apogee Filter(2)

Analyzer

and

Display

Digital

Generator

NOTES: (1) There is little difference in measured THD+N when using the

various settings for these filters. (2) Required for THD+N test.

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