CDB5343 Cirrus Logic Inc, CDB5343 Datasheet - Page 16

• Manufacturer Part Number: CDB5343
• Description: EvalBd 98dB 24-bit 96kHz Stereo ADC
• Manufacturer: Cirrus Logic Inc

Specifications of CDB5343

• Number Of Adc's: 1
• Number Of Bits: 24
• Sampling Rate (per Second): 108k
• Data Interface: Serial
• Inputs Per Adc: 2 Single
• Power (typ) @ Conditions: 60mW @ 5 V
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 85°C
• Utilized Ic / Part: CS5343, CS5344
• Description/function: Audio A/D
• Operating Supply Voltage: 5 V
• Product: Audio Modules
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• For Use With/related Products: CS5343
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant, Contains lead / RoHS non-compliant
• Other names: 598-1156

16
4.4.1
4.5
Grounding and Power Supply Decoupling
As with any high-resolution converter, designing with the CS5343/4 requires careful attention to power sup-
ply and grounding arrangements if its potential performance is to be realized.
mended power arrangements, with VA connected to a clean supply. 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 mod-
ulators. The FILT+ and VQ decoupling capacitors, particularly the 0.1 µF, must be positioned to minimize
the electrical path from FILT+ to GND. The CDB5343 evaluation board demonstrates the optimum layout
and power supply arrangements. To minimize digital noise, connect the ADC digital outputs only to CMOS
inputs.
Component Values
Three parameters determine the values of resistors R1 and R2 as shown in
attenuation, and input impedance.
Figure 7
the discussion above, this circuit provides an optimal interface for both the ADC and the signal source.
First, consumer equipment frequently requires an input impedance of 10 kΩ, which the 4.99 kΩ resistors
provide. Second, this circuit will attenuate a typical line level voltage, 2 Vrms, to the full-scale input of the
ADC, 1 Vrms when VA = 5 V. Finally, at 2.5 kΩ, the source impedance optimizes analog performance of
the ADC.
•
•
•
Source Impedance: Source impedance is defined as the impedance as seen from the ADC looking
back into the signal network. The ADC achieves optimal THD+N performance with a source imped-
ance less than or equal to 2.5 kΩ.
Attenuation: The required attenuation factor depends on the magnitude of the input signal. The full-
scale input voltage is specified under
The user should select values for R1 and R2 such that the magnitude of the incoming signal multiplied
by the attenuation factor is less than or equal to the full-scale input voltage of the device.
Input Impedance: Input impedance is the impedance from the signal source to the ADC analog input
pins, including the ADC. Because the ADC’s input impedance (see the
mercial Grade
typically used for the input attenuator, its contribution can be neglected when calculating the input im-
pedance.
tenuator.
illustrates an example configuration using two 4.99 kΩ resistors in place of R1 and R2. Based on
Table 6
(-CZZ)” table on
Input
Figure 7. CS5343/4 Example Analog Input Network
shows the input parameters and the associated design equations for the input at-
Source Impedance
Attenuation Factor
Table 6. Analog Input Design Parameters
4.99 kΩ
4.99 kΩ
Input Impedance
Table 6
page
“Analog Characteristics - Commercial Grade (-CZZ)” on page
6) is several orders of magnitude larger than the resistor values
1 µF
180pF
C0G
shows the design equation used to determine these values.
4/2/08
Draft
(
------------------------ -
------------------------ -
(
(
R1 R2
R1
R1
R1
(
R2
×
+
+
+
CS5343/4
AIN
R2
R2
R2
)
)
)
)
“Analog Characteristics - Com-
Figure
Figure 3
6: source impedance,
shows the recom-
CS5343/4
DS687F3
6.