HSP50214B
0
2-1
2-2
2-3
2-4
2-5
2-6
2-7
2-8
2-9
2-10
2-11
2-12
2-13
2-14
0
2-1
2-2
2-3
2-4
2-5
2-6
2-7
2-8
2-9
2-10
2-11
2-12
2-13
2-14
0
2-1
2-2
2-3
2-4
2-5
2-6
2-7
2-8
2-9
2-10
2-11
2-12
2-13
2-14
2-15
2-16
2-17
2-18
2-19
2-20
2-21
2-22
2-23
2-24
2-25
2-26
2-27
2-28
2-29
2-30
2-31
2-32
2-33
2-34
2-35
2-36
2-37
2-38
2-39
0
2-1
2-2
2-3
2-4
2-5
2-6
2-7
2-8
2-9
2-10
2-11
2-12
2-13
2-14
2-15
2-16
2-17
2-18
2-19
2-20
2-21
2-22
2-23
2-24
2-25
2-26
2-27
2-28
2-29
2-30
2-31
2-32
2-33
2-34
2-35
0
2-1
2-2
2-3
2-4
2-5
2-6
2-7
2-8
2-9
2-10
2-11
2-12
2-13
2-14
2-15
2-16
2-17
2-18
2-19
2-20
2-21
2-22
2-23
2-24
2-25
2-26
2-27
2-28
2-29
2-30
2-31
0
2-1
2-2
2-3
2-4
2-5
2-6
2-7
2-8
2-9
2-10
2-11
2-12
2-13
2-14
2-15
2-16
2-17
2-18
2-19
2-20
2-21
2-22
2-23
2-24
2-25
2-26
2-27
2-28
2-29
2-30
2-31
0
2-1
2-2
2-3
2-4
2-5
2-6
2-7
2-8
2-9
2-10
2-11
2-12
2-13
2-14
2-15
2-16
2-17
2-18
2-19
2-20
2-21
2-22
2-23
2-24
2-25
2-26
2-27
2-28
2-29
2-30
2-31
0
2-1
2-2
2-3
2-4
2-5
2-6
2-7
2-8
2-9
2-10
2-11
2-12
2-13
2-14
2-15
2-16
2-17
2-18
2-19
2-20
2-21
2-22
2-23
NOTE: If 14 input bits are not needed, the gain adjust can be in-
creased by one for each bit that the input is shifted down
at the input. For example, if only 12-bits are needed, an
offset range of 24dB is possible for a decimation of 24.
FIGURE 16. CIC FILTER BIT WEIGHTING
Since each halfband filter section decimates by 2, the total
decimation through the halfband filter is given by:
DECHB= 2N
(EQ. 9)
where N = Number of Halfband Filters Selected (1 - 5).
HALFBAND
FILTER INPUT
FN = fS
fIN = fS
†
HALFBAND FILTER 1
CONTROL WORD 7, BIT 15
FN = FHB1
01
FHB1 = fS OR fS/2
†
HALFBAND FILTER 2
CONTROL WORD 7, BIT 16
FN = FHB2
01
FHB2 = FHB1 OR FHB1/2
†
HALFBAND FILTER 3
CONTROL WORD 7, BIT 17
FN = FHB3
01
FHB3 = FHB2 OR FHB2/2
†
HALFBAND FILTER 4
CONTROL WORD 7, BIT 18
FN = FHB4
01
FHB4 = FHB3 OR FHB3/2
†
HALFBAND FILTER 5
CONTROL WORD 7, BIT 19
01
F5 = FHB4 OR FHB4/2
HALFBAND
FILTER OUTPUT
† Each halfband section decimates by 2.
FIGURE 17. BLOCK DIAGRAM OF HALFBAND FILTER
SECTION
17
FN4450.4
May 1, 2007