CS5361
4.3 Power-up Sequence
Reliable power-up can be accomplished by keeping the device in reset until the power supplies, clocks and config-
uration 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.
The internal reference voltage must be stable for the device to produce valid data. Therefore, there is a delay be-
tween the release of reset and the generation of valid output, due to the finite output impedance of FILT+ and the
presence of the external capacitance.
4.4 Analog Connections
The analog modulator samples the input at 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 (n × 6.144 MHz) the digital passband frequency,
where n=0,1,2,...Refer to Figure 24 which shows the suggested filter that will attenuate any noise energy at
6.144 MHz, in addition to providing the optimum source impedance for the modulators. The use of capacitors which
have a large voltage coefficient (such as general purpose ceramics) must be avoided since these can degrade signal
linearity.
634 Ω
470 pF
COG
-
91 Ω
10 uF
ADC AIN+
AIN+
+
Ω
100k
10 k Ω
10 k Ω
COG
2700 pF
VQ
10 uF
+
-
AIN-
91 Ω
ADC AIN-
Ω
100k
470 pF
COG
634 Ω
Figure 24. CS5361 Recommended Analog Input Buffer
18
DS467F2
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