Datasheet
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MULTIPLEXER AND PGA
R
IN
(k, typical)
286
1 10
(PGA Gain20)
(1)
LIN+
S0125-01
V
IN
L
L-ch
−1
PGA (−4 dB to 20 dB)
R
R
LIN−
2-ch MUX
RIN+
V
IN
R
R-ch
−1
PGA (−4 dB to 20 dB)
R
R
RIN−
Mic Amp
ANALOG OUTPUTS FROM DAC
VCOM OUTPUT FOR DAC
DIGITAL AUDIO INTERFACE TRANSMITTER (DIT)
PCM3052A
SLES160 – NOVEMBER 2005
The PCM3052A has built-in analog front-end circuit which is shown in Figure 50 . Multiplexer input and PGA gain
are selected by mode control via the serial port, as shown in the Serial Control Port for Mode Control section.
The full-scale input voltage range is 0.1 Vrms to 1.5 Vrms, and it can be adjusted to an adequate level for
following the ADC sections.
V
IN
L and V
IN
R input resistance is maintained above 22 k Ω for all PGA gains. The input resistance value for each
gain can be calculated by Equation 1 .
Figure 50. Multiplexer and PGA
The PCM3052A has two independent output channels, V
OUT
L and V
OUT
R. These are unbalanced outputs, each
capable of driving 4 Vp-p (typical) into a 5-k Ω ac-coupled load. The internal output amplifiers for V
OUT
L and
V
OUT
R are biased to the dc common-mode (or bipolar zero) voltage, equal to 0.5 V
CC
2
The output amplifiers include an RC continuous-time filter, which helps to reduce the out-of-band noise energy
present at the DAC outputs due to the noise-shaping characteristics of the PCM3052A delta-sigma modulators.
The frequency response of this filter is shown in the typical performance curves. By itself, this filter is not
adequate to attenuate the out-of-band noise to an acceptable level for many applications. An external low-pass
filter is required to provide sufficient out-of-band noise rejection. Further discussion of DAC post-filter circuits is
provided in the PCM1742 data sheet (SBAS176 ).
One unbuffered common-mode voltage output pin, V
COM
(pin 26), is brought out for decoupling purposes. This
pin is nominally biased to a dc voltage level equal to 0.5 V
CC
2. This pin can be used to bias external circuits.
Output resistance of this pin is 21 k Ω (typical).
The PCM3052A employs S/PDIF output from DOUTS (pin 14). The data (I
2
S format only) from DAC digital data
input (DIN, pin 12) is encoded to S/PDIF format with preambles according to IEC958. S/PDIF output is controlled
through the serial control port. The output data type (linear PCM or AC-3) can be also selected through the serial
control port. For the output data type of AC-3, the word length is limited to 16 bits in the PCM3052A. Therefore,
bits 17 to 24 in the I
2
S format data must be set to LOW.
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