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Philips Semiconductors
10.3 Audio DAC characteristics
Table 24:
Dynamic characteristics: Audio DAC
Tamb = 0 °C to +70 °C for commercial unless otherwise specified.
Symbol
Parameter
Audio DAC Outputs: ADAC1-12
f
audio sample frequency
s
S/N
Signal to Noise Ratio, CCIR-2 k
weighted
(THD+N)/S Total Harmonic Distortion + Noise to
Signal ratio
f
frequency response
res
α
crosstalk between adjacent DACs
ct
[1]
Allowed audio sample frequencies are 32 kHz, 44.1 kHz and 48 kHz. Default f
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
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 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.
10.4 Timing
10.4.1 Clock
Crystal specification
The crystal oscillator can be used with an external crystal, or in bypass mode with external
clock signal, see
9397 750 13928
Product data
Conditions
-
outputs muted; reference f = 2 kHz,
0 dBFS
f =1 kHz; 0 dBFS; 22 kHz
measurement bandwidth
+/-1 dB
f = 1 kHz; 0 dBFS
Figure
4.
Rev. 03 – 23 August 2004
Audio video input processor
Min
Typ
32
48
-
94
−77
-
<10
-
−90
-
2
in I
S-bus master mode is 48 kHz.
S
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
PNX2000
Max
Unit
[1]
48
kHz
-
dB
-
dB
22.5
kHz
-
dB
,
S
22 of 31
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