AD6652BC/PCB Analog Devices Inc, AD6652BC/PCB Datasheet - Page 36

• Manufacturer Part Number: AD6652BC/PCB
• Description: BOARD EVAL W/AD6652 & SOFTWARE
• Manufacturer: Analog Devices Inc

Specifications of AD6652BC/PCB

• Module/board Type: Evaluation Board
• For Use With/related Products: AD6652
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

AD6652
rCIC2 OUTPUT LEVEL
After the prop
level from the rCIC2 stage can be determined using the
following equation:
where:
input_level is normally full sca
rCIC2 stage.
OL
fraction of the input_level. OL
stage-level calculations.
rCIC2 REJECTION
Table 14
the data rate into the rC
scaled to any other a
table can be u
decimation between rCIC2, CIC5, and the RCF.
Example Calculations:
Goal: Implement a filter with an input sample rate of 10 MHz,
requiring 100 dB of alias rejection for a ±7 kHz pass band.
Solution: First determine the percentage of th
is rep
Then find the −100 dB column on the right of the table and
look down this column for a value greater than or equal to the
pass-band percentage of the clock rate. Then look across to the
extreme left column and find the corresponding rate change
factor (M
M
rejection is 0.071%, which is slightly greater than the 0.07%
calculated. Therefore, for this example, the maximum bound on
rCIC2 rate change is 4. A higher chosen M
alias rejection than the 100 dB required.
An M
rejection; however, power consumption can be minimized by
decimating as much as possible in this rCIC2 stage. Decimation
in rCIC2 lowers the data rate, and, therefore, reduces power
rCIC2
rCIC2
OL
BW
res
/L
rCIC2
is the output level from the rCIC2 stage expressed as a
rCIC2
rCIC
ented by the pass band, as follows:
illustrates the amount o
fraction
rCIC2
/L
2
of 4, the frequency having −100 dB of alias
rCIC2
/L
=
sed as a tool to dec
er scaling factor has been determined, the output
rCIC2
L
=
of less than 4 would still yield the required
rCIC
(
100
M
). Referring to the table, notice that for a
2
llowable sam
rCIC
×
×
2
IC2 stag
2
10
S
2
rCIC
7
)
kHz
MHz
2
rCIC2
le (or 1) from the ADC to the
×
e. T
f bandwid
ide how
input
ple
=
is used later in the CIC5
he data in this table can be
. 0
rate up to 65 MHz. The
07
_
level
to distribute the
rCIC2
th in percentage of
e sample rate that
/L
rCIC2
means less
Rev. 0 | Page 36 of 76
consumed in subsequent stages. It should also be noted that
there is more than one way to get the decimation by 4. A
decimation of 4
integer combination of L/M that yields 0.25 works (1/4, 2/8, o
4/16). However, for the best dynamic range, use the simplest
ratio. For example, 1/4 gives better performance than 4/16.
Table 14. SSB rCIC2 Alias Rejection Table (f
Bandwidth Shown in Percentage of f
M
L
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
DECIMATION AND INTERPOLATION REGISTERS
rCIC2 decimation values are stored in Register 0x90. This 1
register contains the decim
tion portion is stored in Register 0x91. This 9-bit value holds
the interpolation value minus one.
rCIC2 SCALE REGISTER
Register 0x92 contains the scaling information for the rCIC2.
The primary function is to store the scale value computed in the
previous sections.
Bits 4–0 of this register should be written with the same values
as those written to Bits 9–5 to accommodate a redundant
internal hardware feature.
Bits 9–5 (S
Bits 11–10 are reserved and must be written low.
In applications that do not require the features of the rCIC2,
bypass it by setting the L/M ratio to 1/1. This effectively
bypasses all circuitry of the rCIC2 except the scaling, which is
still effectual.
rCIC2
rCIC2
/
−50 dB
1.79
1.508
1.217
1.006
0.853
0.739
0.651
0.581
0.525
0.478
0.439
0.406
0.378
0.353
0.331
rCIC2
) contain the 5-bit scaling factor for rCIC2.
is the same as an L/M ratio of 0.25. Thus, any
−60 dB
1.007
0.858
0.696
0.577
0.49
0.425
0.374
0.334
0.302
0.275
0.253
0.234
0.217
0.203
0.19
ation value minus 1. The interpola-
−70 dB
0.566
0.486
0.395
0.328
0.279
0.242
0.213
0.19
0.172
0.157
0.144
0.133
0.124
0.116
0.109
−80 dB
0.318
0.274
0.223
0.186
0.158
0.137
0.121
0.108
0.097
0.089
0.082
0.075
0.07
0.066
0.061
SAMP
−90 dB
0.179
0.155
0.126
0.105
0.089
0.077
0.068
0.061
0.055
0.05
0.046
0.043
0.04
0.037
0.035
SAMP
= 1)
−100 d
0.101
0.087
0.071
0.059
0.05
0.044
0.038
0.034
0.031
0.028
0.026
0.024
0.022
0.021
0.02
2-bit
r
B