UDA1338H 데이터 시트보기 (PDF) - Philips Electronics
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UDA1338H Datasheet PDF : 56 Pages
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Philips Semiconductors
Multichannel audio coder-decoder
Preliminary specification
UDA1338H
8.2 Audio analog-to-digital converter (audio ADC)
The audio analog-to-digital front-end of the UDA1338H
consists of 4-channel single-ended Adds with
programmable gain stage (from 0 to 24 dB with 3 dB
steps), controlled via the microcontroller interface. Using
the PGA feature, it is possible to accept an input signal of
900 mV (RMS) or 1.8 V (RMS) if an external resistor of
10 kΩ is used in series. The schematic of audio ADC
front-end is shown in Fig.3.
handbook, halfpage
input signal
2 V (RMS)
VINL,
10 kΩ VINR
10 kΩ (0 dB setting)
10 kΩ
ADC
Vref
VDDA = 3.3 V
MGU582
Fig.3 Schematic of audio ADC front-end.
8.5 Decimation filter of voice ADC
The voice ADC decimation filter is realized with the
combination of a Finite Impulse Response (FIR) filter and
Infinite Impulse Response (IIR) filter for shorter group
delay. The filter characteristics are shown in Table 5.
During the power-on sequence, the output of the ADC is
hard muted for a certain period. This hard-mute time can
be chosen between 1024 and 2048 samples.
Table 5 Decimation filter characteristics (voice ADC)
ITEM
Pass-band ripple
Pass-band droop
Stop band
Dynamic range
CONDITION
0 to 0.45fs
0.45fs
>0.55fs
0 to 0.45fs
VALUE (dB)
±0.05
−0.2
−65
>110
8.6 Interpolation filter of DAC
The digital interpolation filter interpolates from 1fs to 128fs
(or to 64fs in the 192 kHz sampling mode) by cascading
FIR filters, and has two sets of filter coefficients for sharp
and slow roll-off as given in Tables 6 and 7.
8.3 Voice analog-to-digital converter (voice ADC)
The voice analog-to-digital front-end of the UDA1338H
consists of a single-channel single-ended ADC with a fixed
gain (26 dB) Low Noise Amplifier (LNA). Together with the
digital variable gain amplification stage, the voice ADC
provides optimal processing and reproduction of the
microphone signal. The supported sampling frequency
range is from 7 to 50 kHz. Power-down of the LNA and the
ADC can be controlled separately.
8.4 Decimation filter of audio ADC
The decimation from 64fs is performed in two stages.
The first stage realizes
-s---i-xn----x--
4
characteristics with a
decimation factor of 8. The second stage consists of three
half-band filters, each decimating by a factor of 2. The filter
characteristics are shown in Table 4.
Table 4 Decimation filter characteristics (audio ADC)
ITEM
Pass-band ripple
Pass-band droop
Stop band
Dynamic range
CONDITION
0 to 0.45fs
0.45fs
>0.55fs
0 to 0.45fs
VALUE (dB)
±0.01
−0.2
−70
>135
Table 6 Interpolation filter characteristics (sharp roll-off)
ITEM
Pass-band ripple
Stop band
Dynamic range
CONDITION
0 to 0.45fs
>0.55fs
0 to 0.45fs
VALUE (dB)
±0.002
−75
>135
Table 7 Interpolation filter characteristics (slow roll-off)
ITEM
Pass-band ripple
Pass-band droop
Stop band
Dynamic range
CONDITION
0 to 0.22fs
0.45fs
>0.78fs
0 to 0.22fs
VALUE (dB)
±0.002
−3.1
−94
>135
8.7 Noise shaper of DAC
The 3rd-order noise shaper operates at either 128fs or 64fs
(in the 192 kHz sampling mode), and converts the 24-bit
input signal into a 5-bit signal stream. The noise shaper
shifts in-band quantization noise to frequencies well above
the audio band. This noise shaping technique enables
high signal-to-noise ratios to be achieved.
2002 Nov 21
9
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