Philips PNX2000 10.3 Audio DAC characteristics, 10.4 Timing

Product data Rev. 03 – 23 August 2004 22 of 31

Philips Semiconductors PNX2000

Audio video input processor

10.3 Audio DAC characteristics

[1] Allowed audio sample frequencies are 32 kHz, 44.1 kHz and 48 kHz. Default fS in I2S-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

AD A Cn. Co nsequently it is important to provide adeq uate filtering of the r ef ere nce v oltag e

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 diffe rence will degrade

distortion performan ce.

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

using a noise shaper circuit to shift the quantization noise to out-of-band frequencies. To

pre vent HF overloading of the circuit that is driven by the D AC outputs , a 3.3 nF capacito r

should be used to filter off the HF signal content. Together with the DAC’s nominal output

impedance of 1 kΩ, 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.

Crystal specification

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

clock signal, see Figure 4.

Table 24: Dynamic characteristics: Audio DAC

Tamb = 0 °C to +70 °C for commercial unless otherwise specified.

Symbol Parameter Conditions Min Typ Max Unit

Audio DAC Outputs: ADAC1-12

fsaudio sample frequency - 32 48[1] 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

fres frequency response +/-1 dB <10 - 22.5 kHz

αct crosstalk between adjacent DACs f = 1 kHz; 0 dBFS - −90 - dB