CS4344/5/6/8
DS613PP2 15
4.4 Initialization and Power-Down
The Initialization and Power-Down sequence flow chart is shown in Figure 12. The CS4344 family enters
the Power-Down State upon initial power-up. The interpolation filters and delta-sigma modulators are re-
set, and the internal voltage reference, multi-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 counted over one LRCK period
to determine the MCLK/LRCK frequency ratio. Power is then applied to the internal voltage reference. Fi-
nally, power is applied to the D/A converters and switched-capacitor filters, and the analog outputs will ramp
to the quiescent voltage, VQ.
4.5 Output Transient Control
The CS4344 family uses Popguard
™
technology to minimize the effects of output transients during power-
up and power-down. This technique eliminates 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 understand its operation.
4.5.1 Power-up
When the device is initially powered-up, the audio outputs, AOUTL and AOUTR, are clamped to VQ
which is initially low. After MCLK is applied the outputs begin to ramp with VQ towards the nominal
quiescent voltage. This ramp takes approximately 250 ms with a 3.3 µF cap connected to VQ (420 ms
with a 10 µF connected to VQ) to complete. The gradual voltage ramping allows time for the external
DC-blocking capacitors to charge to VQ, effectively blocking the quiescent DC voltage. Once valid
LRCK and SDIN are supplied (and SCLK if used) approximately 2000 sample periods later audio out-
put begins.
4.5.2 Power-down
To prevent audio transients at power-down the DC-blocking capacitors must fully discharge before
turning off the power. In order to do this MCLK should be stopped for a period of about 250 ms for a
3.3 µF cap connected to VQ (420 ms for a 10 µF cap connected to VQ) before removing power. Dur-
ing this time voltage on VQ and the audio outputs discharge gradually to GND. If power is removed
before this time period has passed a transient will occur when the VA supply drops below that of VQ.
There is no minimum time for a power cycle, power may be re-applied at any time.
Gain
dB
-10dB
0dB
Frequency
T2 = 15 µs
T1=50 µs
F1 F2
3.183 kHz 10.61 kHz
Figure 11. De-Emphasis Curve (Fs = 44.1kHz)
