AD6620S/PCB Analog Devices Inc, AD6620S/PCB Datasheet - Page 23

• Manufacturer Part Number: AD6620S/PCB
• Description: BOARD EVAL DUAL RCVR W/AD6620AS
• Manufacturer: Analog Devices Inc

Specifications of AD6620S/PCB

• Rohs Status: RoHS non-compliant
• Module/board Type: Evaluation Board
• For Use With/related Products: AD6620

5TH ORDER CASCADED INTEGRATOR COMB FILTER
The third signal processing stage, CIC5, implements a sharper
fixed-coefficient, decimating filter than CIC2. The input rate to
this filter is f
equation below. N
input mode; otherwise N
equation, M
can be increased (reference fractional rate input timing described
in the Input Timing section).
The decimation ratio, M
(all integer values). When M
the CIC5 scale factor is ignored.
–100
–120
–100
–120
–20
–40
–60
–80
–20
–40
–60
–80
–0.5
–0.5
0
0
CIC2
SAMP2
–0.4 –0.3 –0.2
–0.4 –0.3 –0.2
can be increased, N
. The maximum input rate is given by the
CH
equals two for Diversity Channel Real
f
SAMP
CIC5
CH
–0.1
–0.1
equals one. In order to satisfy this
, may be programmed from 1 to 32
CIC5
2
f/f
≤
f/f
SAMP
SAMP2
2
= 1, this stage is bypassed and
0
0
×
f
CLK
N
CH
0.1
0.1
CH
can be reduced, or f
0.2
0.2
0.3
0.3
0.4
0.4
0.5
0.5
CLK
The frequency response of the filter is given by the following
equations. The gain and pass band droop of CIC5 should be
calculated by these equations. Both parameters may be compen-
sated for in the RCF stage.
The scale factor, S
between 0 and 20. It serves to control the attenuation of the
data into the CIC5 stage in 6 dB increments. For the best dynamic
range, S
attenuation) without creating an overflow condition. This can
be safely accomplished using the equation below, where OL
is the largest fraction of full scale possible at the input to this
filter stage. This value is output from the CIC2 stage then pipe-
lined into the CIC5. S
by setting M
when CIC5 is bypassed;
The output rate of this stage is given by the equation below.
CIC5
S
H f
CIC5
should be set to the smallest value possible (lowest
CIC
( )
5
= 1.
OL
=
H z
=
CIC5
ceil
( )
2
CIC
S
CIC5
CIC
1
OL
=
is a programmable unsigned integer
(
5
f
5
log (
SAMP
+
2
=
5
is ignored when this filter is bypassed
S
CIC
CIC
(
×
2
1
M
2
5
5






M
5
+
S
5
CIC
CIC
sin
≤
=
×
CIC
sin
5
f
M
+
OL



5
SAMP
5
1
5



5
)
π
CIC
–
5
1



CIC
×
π
z
–
×
M
5
2
–
OL
z
OL
2
f
f
M
CIC
SAMP
SAMP
–
1
CIC
f
CIC
CIC
5
5



×
5
2
2
2
2



f
) –
AD6620
)









5
5
CIC2