GC4016 Datasheet, PDF (65/83 Pages) Texas Instruments – MULTI-STANDARD QUAD DDC CHIP

GC4016 MULTI-STANDARD QUAD DDC CHIP
DATA SHEET REV 1.0
7.7 EXAMPLE RESAMPLER CONFIGURATIONS
This Section describes some commonly used resampler configurations and the filter coefficient sets used for them.
7.7.1 Bypass Mode
The resampler is bypassed by using a configuration which has h₀ set to 1024, all other taps set to zero, NMULT set to 7,
NO_SYM_RES set to 1, FINAL_SHIFT set to 5, and RATIO set to 2²⁶ (0x04000000). Note that the NDELAY term in the
RES_GAIN equation does not apply in this case and should be set to unity in the gain equation. The resampler control register
setting for this mode are shown in Table 27.
Table 27: Resampler Bypass Mode
Address
Page 32
Pages 33-63
Page 64
Page 65
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
00 04 00
00
23 46 00 35 E4 70 00 00 unused
00 00 00 04 00 00 00 04 00 00 00 04 00 00 00 04
7.7.2 Resampling Modes
Several resampler configurations are summarized in Table 28. These configurations use the default values for the resampler
controls except for NMULT in address 17, which must be set to the value in Table 28. The defaults (hex) are 23, NM, 00, 34, E4,
00, 00 and 00, respectfully for addresses 16 through 23 of page 64. NM is NMULT-1.
Table 28: Resampler Modes
Configuration
Name
NMULT
%BW
PB
Ripple
(dB)
Image
Rejection
(dB)
RES_SUM
Application
Configurations with NDELAY = 64,
These offer the best resampling phase jitter performance (-48dB inband noise), but the % input bandwidth must be 60% or less
res_6x64_60
6
60
0.18
52
134786
Use if NMULT must be 6
res_7x64_60
7
0.16
55
138292
Use if NMULT must be less than 8
res_8x64_60
8
60
0.03
62
134782
SUGGESTED DEFAULT-
Best 60% bandwidth mode, Adequate for most applications
res_8x64_80
80
0.7
43
139894
An 80% mode with NMULT=8
Configurations with NDELAY = 32,
These offer higher % bandwidth, but fewer resampling delays (-42dB inband jitter noise)
res_9x32_60
9
60
0.01
63
64700
Best 60% mode for interpolating by integer amounts
res_12x32_80
12
80
0.11
48
65610
Alternate if NMULT must be less than 15
res_15x32_80
15
0.05
58
66482
Best 80% mode, Very good for interpolating by integer amounts
Configurations with NDELAY = 16,
These are restricted to single or dual channel modes, very good for interpolating by integer amounts.
res_19x16_80
19
80
0.02
65
32988
Good filter, but only for single or dual channel modes
The %BW column reflects the percentage passband of the signal relative to the sample rate going into the resampler. The
resampler’s response is flat over this bandwidth to within the passband ripple indicated above. The image rejection is the amount
that the resampling images are rejected relative to the signal.
The filter taps for these configurations can be requested by e-mail from [e-mail], or downloaded from
the web at www.graychip.com. The filter taps are available in two file formats. The first, <filter_name>.taps, is an ascii listing of
the taps. The second, <filter_name>.cmd, is a command file which could be used to write the filter taps into a GC4016 chip. The
commands are formatted as “write <address> <data_byte>”, where <address> and <data_byte> are unsigned hex integers.
© GRAYCHIP,INC.
- 60 -
August 27, 2001
This document contains information which may be changed at any time without notice