AD6652BC/PCB Analog Devices Inc, AD6652BC/PCB Datasheet - Page 35

• 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

SECOND-ORDER rCIC FILTE
The rCIC2 filter is a second-order resampling cascaded
integrator comb filter. The resampler is implemented using a
unique technique, which does not require the use of a high-
speed clock, thus simplifying the design and saving power. The
resampler allows for noninteger relationships between the D
CLK and the output data rate. This allows easier implemen
tion of systems that are either multimode or require a master
clock that is not a multiple of the data rate to be used.
Interpolation up to 512 and decimation up to 4096 is al
the rCIC2. The resampling factor for the rCIC2 (L) is a 9-bit
integer. When combined with the decimation factor M, a 12-bit
number, the total rate-change can be any fraction in the form of
The only co
equal to one. This implies that the rC
more.
Resampling is implemented by apparently increasing the input
sample rate by the factor L, using zero stuffing for the new data
samples. Following the resampler is
integrator comb filter. Filter chara
by the fractional rate-change (L/M
The filter can process signals at the full rate of the input po
(65 MHz). The output rate of this stage is given by the followin
equation:
where:
L
L
M
The stage can be bypassed
frequency response of the
equations:
rCIC2
rCIC2
rCIC2
, the interpolation rate, can be from 1 to 512.
R
R
H
and M
f
, the decimation, can be between 1 and 4096.
SAMP
rCIC
rCIC
(
z
)
2
2
=
=
≤
nstraint is that the ratio L/M must be less
2
rCIC2
2
1
=
M
L
S
rCIC
L
are unsigned integers.
rCIC
2
M
1
×
L
2
rCIC
rCIC
f
SAMP
2
2
rCIC2 filter is given by the following
by setting the decimation to 1/1. The
×
⎛
⎜
⎜
⎜
⎜
⎜
⎝
1
−
cteristics are determined only
1
).
z
−
a second-order cascaded
M
IC2 decimates by 1 or
L
z
rCIC
rCIC
−
1
2
2
R
⎞
⎟
⎟
⎟
⎟
⎟
⎠
2
than or
lowed in
ta-
rt
DC
Rev. 0 | Page 35 of 76
g
Use these equations along with the following filter transfer
equations to calculate the gain and pass-band droop of the
rCIC2. Excessive pass-band droop can be compensated for in
the RCF stage by peaking the pass-band by the inverse of the
roll-off.
rCIC2 SCALE FACTOR
The scale factor, S
between 0 and 31, which serves as an attenuator that can reduce
the gain of the rCIC2 in 6 dB increments. For the best dynami
range, set S
overflow condition. This can be safely accomplished using the
following equation, where input_level is the largest fraction of
full scale possible at the input to the AD6652 (normally 1). The
S
bypassed.
The S
decimation rates must be adjusted to validate this equation. The
ceil function denotes the next whole integer, and the floor
function denotes the current whole integer. For example, the
ceil(4.2) is 5 while the floor(4.2) is 4. When S
determined for all channels, i
[9:5] of each channel
als
ha
The gain and p
lated by the previous equations, as well as the rCIC2 filter
transfer equations. Excessive pass-band droop can be compen-
sated for in the RCF stage by peaking the pass-band by the
inverse of the roll-off.
rCIC2
rdware feature.
o be programmed a
H
S
scale factor is always used whether or not the rCIC2 is
rCIC2
rCIC
(
f
2
)
value must be less than 32 or the interpolation and
rCIC2
=
=
2
ceil
S
ass-band d
to the least attenuation without creating an
rCIC
⎡
⎢
⎢
⎢
⎢
⎢
⎢
⎣
rCIC2
log
2
1
×
, is a programmable unsigned 5-bit
addr
2
L
t 0x92[4:0] t
⎛
⎜
⎜
⎜
⎜
⎜
⎜
⎝
rCIC
⎛
⎜
⎜
⎝
M
2
roop
ess register. The sam
rCIC
×
2
M
t must be programmed at 0x92
×
2
rCIC
of the rCIC2 shoul
+
⎛
⎜
⎜
⎜
⎜
⎜
⎜
⎝
sin
floor
2
o accommo
−
⎛
⎜
⎜
⎝
L
π
sin
⎛
⎜
⎜
⎝
rCIC
L
M
L
rCIC
⎛
⎜
⎜
⎝
2
M
rCIC
π
rCIC
×
rCIC2
rCIC
f
2
floor
2
date
SAMP
e va
2
×
f
⎞
⎟
⎟
⎠
has been
2
d be calcu-
×
f
lue sho
×
a redundan
SAMP
⎛
⎜
⎜
⎝
⎞
⎟
⎟
⎠
AD6652
M
L
f
rCIC
rCIC
⎞
⎟
⎟
⎠
uld
2
⎞
⎟
⎟
⎟
⎟
⎟
⎟
⎠
2
2
+1
c
t
⎞
⎟
⎟
⎠
⎞
⎟
⎟
⎠
⎞
⎟
⎟
⎟
⎟
⎟
⎟
⎠
⎤
⎥
⎥
⎥
⎥
⎥
⎥
⎦