CS4215 datasheet(29/52 Pages) CIRRUS

29 / 52 page

placed closest to the codec. Vias are placed near

the AGND and DGND pins, under the IC, and

should be attached to the solid analog ground

plane on another layer. The negative side of the

decoupling capacitors should also attach to the

same solid ground plane. Traces bringing the

power to the codec should be wide thereby keep-

ing the impedance low.

Although not shown in the figures, the trace lay-

ers (top layer in the figures) should have ground

plane fill in-between the traces to minimize cou-

pling into the analog section. See the CDB4215

evaluation board data sheet for an example lay-

out.

If using all surface-mount components, the de-

coupling capacitors should still be placed on the

layer with the codec and in the positions shown

in Figure 20. The vias shown are assumed to at-

tach to the appropriate power and analog ground

layers. Traces bringing power to the codec

should be as wide as possible to keep the imped-

ance low. For the same reason, vias should be

large for power and ground runs.

If using through-hole sockets, effort should be

made to find a socket with the minimum height

which will minimize the socket impedance.

When using a through-hole socket, the vias un-

der the codec in Figure 19 are not needed since

the pins serve the same function.

ADC and DAC Filter Response Plots

Figures 21 through 27 show the overall fre-

quency response, passband ripple and transition

band for the CS4215 ADCs and DACs. Fig-

ure 27 shows the DACs’ deviation from linear

phase. Fs is the selected sample frequency. Since

the sample frequency is programmable, the fil-

ters will adjust to the selected sample frequency.

Fs is also the FSYNC frequency.

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Input Frequency (Fs)

Figure 21. ADC Frequency Response

0.0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50

Input Frequency (Fs)

-0.8

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

-0.0

0.1

0.2

Figure 22. ADC Passband Ripple

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0.40 0.42 0.44 0.46 0.48 0.50 0.52 0.54 0.56 0.58 0.60

Input Frequency (Fs)

Figure 23. ADC Transition Band

CS4215

DS76F2

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