18 DS564F2
CS5341
Confidential Draft
3/11/08
4.4 Power-Up Sequence
Reliable power-up can be accomplished by keeping the device in reset until the power supplies, clocks and
configuration pins are stable. It is also recommended that reset be enabled if the analog or digital supplies
drop below the minimum specified operating voltages to prevent power-glitch-related issues.
4.5 Analog Connections
The analog modulator samples the input at half of the MCLK frequency, or nominally 6.144 MHz. The digital
filter will reject signals within the stopband of the filter. However, there is no rejection for input signals which
are multiples of the input sampling frequency (n
× 6.144 MHz), where n=0,1,2,... Refer to Figure 21, which
shows the suggested filter that will attenuate any noise energy at 6.144 MHz in addition to providing the op-
timum source impedance for the modulators. The use of capacitors that have a large voltage coefficient
(such as general-purpose ceramics) must be avoided since these can degrade signal linearity.
4.6 Grounding and Power Supply Decoupling
As with any high resolution converter, achieving optimal performance from the CS5341 requires careful at-
tention to power supply and grounding arrangements. Figure 17 shows the recommended power arrange-
ments, with VA and VL connected to clean supplies. VD, which powers the digital filter, may be run from the
system logic supply or may be powered from the analog supply via a resistor. In this case, no additional
devices should be powered from VD. Decoupling capacitors should be as near to the ADC as possible, with
the low-value ceramic capacitor being the nearest. All signals, especially clocks, should be kept away from
the FILT+ and VQ pins in order to avoid unwanted coupling into the modulators. The FILT+ and VQ decou-
pling capacitors, particularly the 0.01 µF, must be positioned to minimize the electrical path from FILT+ and
REF_GND. Furthermore, all ground pins on CS5341 should be referenced to the same ground reference.
The CDB5341 evaluation board demonstrates the optimum layout and power supply arrangements. To min-
imize digital noise, connect the ADC digital outputs only to CMOS inputs.
4.7 Synchronization of Multiple Devices
In systems where multiple ADCs are required, the user can achieve simultaneous sampling if the MCLK and
LRCK signals are the same for all of the CS5341’s in the system. If only one master clock source is needed,
one solution is to place one CS5341 in Master Mode, and slave all of the other CS5341’s to the one master.
If multiple master clock sources are needed, a possible solution would be to supply all clocks from the same
external source and time the CS5341 reset with the inactive (falling) edge of MCLK. This will ensure that all
converters begin sampling on the same clock edge.
VA
4.7 µF
470 pF
C0G
2700 pF
CS5341 AINx
AINx
100 kΩ
100 kΩ
634 Ω
91 Ω
Figure 21. CS5341 Recommended Analog Input Buffer
