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MULTIPLEXER AND PGA

R

IN(kW, typical) +

286

1

) 10(PGA Gain 20)

(1)

LIN+

S0125-01

VINL

L-ch

−1

PGA (−4 dB to 20 dB)

R

R

LIN−

2-ch MUX

RIN+

VINR

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.

VINL and VINR input resistance is maintained above 22 kΩ 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, VOUTL and VOUTR. 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

OUTL and

VOUTR are biased to the dc common-mode (or bipolar zero) voltage, equal to 0.5 VCC2

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, VCOM (pin 26), is brought out for decoupling purposes. This

pin is nominally biased to a dc voltage level equal to 0.5 VCC2. 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 (I2S 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 I2S format data must be set to LOW.

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