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KEY PERFORMANCE PARAMETERS AND MEASUREMENT

TOTAL HARMONIC DISTORTION + NOISE

S/PDIF

Receiver

Evaluation Board

DEM-DAI1609A

PCM1609A

2nd-Order

Low-Pass

Filter

Notch Filter

Band Limit

Analyzer

and

Display

Digital

Generator

S/PDIF

Output

100% Full-Scale

24-Bit, 1-kHz

Sine Wave

rms Mode

HPF = 22 Hz(1)

LPF = 30 kHz(1)

Option = 20-kHz Apogee Filter(2)

fC = 1 kHz

f–3 dB = 54 kHz

B0062-03

DYNAMIC RANGE

PCM1609A

SLES145A – AUGUST 2005 – REVISED AUGUST 2006

This section provides information on how to measure key dynamic performance parameters for the PCM1609A.

In all cases, a System Two Cascade audio measurement system by Audio Precision or equivalent is used to

perform the testing.

Total harmonic distortion + noise (THD+N) is a significant figure of merit for audio DACs, because 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 measurements is shown in

Figure 39.

(1)

There is little difference in measured THD+N when using the various settings for these filters.

(2)

Required for THD+N test

Figure 39. Test Setup for THD+N Measurements

For the PCM1609A DACs, THD+N is measured with a full-scale, 1-kHz 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 44.1

kHz or 96 kHz. 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

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

analyzer and displayed by the measurement system.

Dynamic range is specified as A-weighted THD+N measured with a –60-dBFS, 1-kHz digital sine wave stimulus

at the input of the DAC. This measurement is designed to give a good indication of how the DAC performs,

given a low-level input signal.

The measurement setup for the dynamic range measurement is shown in Figure 40, and is similar to the THD+N

test setup discussed previously. The differences include the band-limit filter selection, the additional A-weighting

filter, and the –60-dBFS input level.

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