Datasheet

PCM1753
PCM1754
PCM1755
SLES092C – OCTOBER 2003 – REVISED FEBRUARY 2009
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23
ZREV: Zero Flag Polarity Select
Default value: 01h
ZREV = 0
High on zero flag pins indicates a zero detect (default)
ZREV = 1 Low on zero flag pins indicates a zero detect
The ZREV bit allows the user to select the polarity of zero flag pins.
AZRO: Zero Flag Function Select
Default value: 0
AZRO = 0
L-/R-channel independent zero flags (default)
AZRO = 1 L-/R-channel common zero flag
The AZRO bit allows the user to select the function of zero flag pins.
AZRO = 0:
Pin 11: ZEROR, zero flag output for R-channel
Pin 12: ZEROL, zero flag output for L-channel
AZRO = 1: Pin 11: ZEROA, zero flag output for L-/R-channels
Pin 12: NA, not assigned
ANALOG OUTPUTS
The PCM1753/54/55 includes two independent output channels, V
OUT
L and V
OUT
R. These are unbalanced
outputs, each capable of driving 4 V
PP
typical into a 5-kΩ 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
.
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 PCM1753/54/55 delta-sigma D/A
converters. 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. 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.
−60
−50
−40
−30
−20
−10
0
10
f – Frequency – kHz
Level – dB
LEVEL
vs
FREQUENCY
0.1 100 1k 10k1 10
Figure 26. Output Filter Frequency Response