Справочник Пользователя для Philips PNX2000

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© Koninklijke Philips Electronics N.V. 2004. All rights reserved.

[1]

Allowed audio sample frequencies are 32 kHz, 44.1 kHz and 48 kHz. Default f

S

 in I

2

S-bus master mode is 48 kHz.

The audio DACs are based on a switched-resistor architecture which acts as a controlled 
voltage divider between the positive and negative references ADACn_P and ADACn_N. 
Therefore all noise on the reference pins will spread directly to the associated output pin 
ADACn. Consequently it is important to provide adequate filtering of the reference voltage 
to allow optimum signal-to-noise performance. Also, the voltage difference between 
ADACn_P and SDAC_3V3 should be kept to a minimum as any difference will degrade 
distortion performance.

The DACs have an internal resolution of 4 bits, running at a clock frequency of 128 f

S

, 

using a noise shaper circuit to shift the quantization noise to out-of-band frequencies. To 
prevent HF overloading of the circuit that is driven by the DAC outputs, a 3.3 nF capacitor 
should be used to filter off the HF signal content. Together with the DAC’s nominal output 
impedance of 1 k

Ω

, a first order roll-off at approximately 50 kHz will result. One capacitor 

is required for each DAC output, connected between ADACn and the corresponding 
ADACn_N.

The crystal oscillator can be used with an external crystal, or in bypass mode with external 
clock signal, see 

°

°

f

s

audio sample frequency

-

32

48

48

kHz

S/N

Signal to Noise Ratio, CCIR-2 k 
weighted

outputs muted; reference f = 2 kHz, 
0 dBFS

-

94

-

dB

(THD+N)/S

Total Harmonic Distortion + Noise to 
Signal ratio

f =1 kHz; 0 dBFS; 22 kHz 
measurement bandwidth

-

−

77

-

dB

f

res

frequency response

+/-1 dB

<10

-

22.5

kHz

α

ct

crosstalk between adjacent DACs

f = 1 kHz; 0 dBFS

-

−

90

-

dB