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ANALOG OUTPUTS

0.1

1

10

100

1K

10K

0

−10

−20

−30

−40

−50

−60

Frequency (kHz)

PCM1742

SBAS176A – DECEMBER 2000 – REVISED APRIL 2005

The PCM1742 includes two independent output channels: VOUTL and VOUTR. These are unbalanced outputs,

each capable of driving 3.1 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 VCC/2.

The output amplifiers include an RC continuous-time filter that helps to reduce the out-of-band noise energy

present at the DAC outputs, due to the noise shaping characteristics of the PCM1742 delta-sigma DACs. The

frequency response of this filter is shown in Figure 26. By itself, this filter is not enough to attenuate the

out-of-band noise to an acceptable level for many applications; therefore, 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

Applications Information section of this data sheet.

Figure 26. Output Filter Frequency Response

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