CS4334 Datasheet, PDF (13/26 Pages) Cirrus Logic – 8-Pin, 24-Bit, 96 kHz Stereo D/A Converter

CS4334/5/6/7/8/9
Gain
dB
0dB
T1=50 µs
-10dB
T2 = 15 µs
F1
3.183 kHz
F2 Frequency
10.61 kHz
Figure 9. De-Emphasis Curve (Fs = 44.1kHz)
The interpolation filters and delta-sigma modula-
tors are reset, and the internal voltage reference,
one-bit digital-to-analog converters and switched-
capacitor low-pass filters are powered down. The
device will remain in the Power-Down mode until
MCLK and LRCK are present. Once MCLK and
LRCK are detected, MCLK occurrences are count-
ed over one LRCK period to determine the
MCLK/LRCK frequency ratio. Power is then ap-
plied to the internal voltage reference. Finally, pow-
er is applied to the D/A converters and switched-
capacitor filters, and the analog outputs will ramp to
the quiescent voltage, V_Q.
4.5 Output Transient Control
The CS4334 family uses Popgaurd^® technology to
minimize the effects of output transients during
power-up and power-down. This technique elimi-
nates the audio transients commonly produced by
single-ended single-supply converters when it is
implemented with external DC-blocking capacitors
connected in series with the audio outputs. To
make best use of this feature, it is necessary to un-
derstand its operation.
When the device is initially powered-up, the audio
outputs, AOUTL and AOUTR, are clamped to
AGND. After a short delay of approximately 1000
sample periods, each output begins to ramp to-
wards its quiescent voltage, V_Q. Approximately
10,000 sample cycles later, the outputs reach V_Q
and audio output begins. This gradual voltage
ramping allows time for the external DC-blocking
capacitor to charge to V_Q, effectively blocking the
quiescent DC voltage.
To prevent transients at power-down, the device
must first enter its power-down state. This is ac-
complished by removing MCLK or LRCK. When
this occurs, audio output ceases and the internal
output buffers are disconnected from AOUTL and
AOUTR. A soft-start current sink is substituted in
place of AOUTL and AOUTR which allows the
DC-blocking capacitors to slowly discharge. Once
this charge is dissipated, the power to the device
may be turned off, and the system is ready for the
next power-on.
To prevent an audio transient at the next power-on,
the DC-blocking capacitors must fully discharge
before turning off the power or exiting the power-
down state. If full discharge does not occur, a tran-
sient will occur when the audio outputs are initially
clamped to AGND. The time that the device must
remain in the power-down state is related to the
value of the DC-blocking capacitance. For exam-
ple, with a 3.3 µF capacitor, the time that the device
must remain in the power-down state will be ap-
proximately 0.4 seconds.
4.6 Grounding and Power Supply
Decoupling
As with any high resolution converter, the CS4334
family requires careful attention to power supply
and grounding arrangements to optimize perfor-
mance. Figure 7 shows the recommended power ar-
rangement with VA connected to a clean +5V
supply. For best performance, decoupling capaci-
tors should be located as close to the device pack-
age as possible with the smallest capacitor closest.
4.7 Analog Output and Filtering
The analog filter present in the CS4334 family is a
switched-capacitor filter followed by a continuous
time low pass filter. Its response, combined with
that of the digital interpolator, is given in Figures
17 - 24.
DS248PP3
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