Datasheet

DAC5682Z
www.ti.com SLLS853E –AUGUST 2007–REVISED AUGUST 2012
Table 5. FIR0 and FIR1 Digital Filter Taps
TAP# COEFF TAP# COEFF
1, 47 –5 2, 46 0
3, 45 18 4, 44 0
5, 43 –42 6, 42 0
7, 41 85 8, 40 0
9, 39 –158 10, 38 0
11, 37 272 12, 36 0
13, 35 –444 14, 34 0
15, 33 704 16, 32 0
17, 31 –1106 18, 30 0
19, 29 1795 20, 28 0
21, 27 –3295 22, 26 0
23, 25 10368 — —
24 16384 — —
DUAL-CHANNEL REAL UPCONVERSION
The DAC5682Z can be used in a dual channel mode with real upconversion by mixing with a 1, –1, … sequence
in the signal chain to invert the spectrum. This mixing mode maintains isolation of the A and B channels. The two
points of mixing, CMIX0 and CMIX1, follow each FIR filter. The mixing modes for each CMIX block are controlled
by CMIX0_mode(1:0) and CMIX1(1:0) in register CONFIG2. The wide bandwidths of both FIR0 and FIR1 (40%
passband) provide options for setting the frequency ranges listed in Table 6. With the High Pass (2x2 HP mode),
High Pass/Low Pass (2X4 HP/LP mode) and Low Pass/High Pass (2X4 LP/HP mode) settings, the upconverted
signal is spectrally inverted.
Table 6. Dual-Channel Real Upconversion Options
FIR0, FIR1,
INTERP. INPUT OUTPUT SIGNAL SPECTRUM
MODE NAME CMIX0 CMIX1
FACTOR FREQUENCY
(1)
FREQUENCY
(1)
BANDWIDTH
(1)
INVERTED?
MODE MODE
2X2 X2 -- LP 0.0 to 0.4 × f
DATA
0.0 to 0.4 × f
DATA
0.4 × f
DATA
No
2X2 HP X2 -- HP 0.0 to 0.4 × f
DATA
0.6 to 1.0 × f
DATA
0.4 × f
DATA
Yes
1X4 X4 LP LP 0.0 to 0.4 × f
DATA
0.0 to 0.4 × f
DATA
0.4 × f
DATA
No
2X4 X4 LP LP 0.0 to 0.4 × f
DATA
0.0 to 0.4 × f
DATA
0.4 × f
DATA
No
2X4 HP/LP X4 HP LP 0.2 to 0.4 × f
DATA
0.6 to 0.8 × f
DATA
0.2 × f
DATA
Yes
2X4 HP/HP X4 HP HP 0.2 to 0.4 × f
DATA
1.2 to 1.4 × f
DATA
0.2 × f
DATA
No
2X4 LP/HP X4 LP HP 0.0 to 0.4 × f
DATA
1.6 to 2.0 × f
DATA
0.4 × f
DATA
Yes
(1) f
DATA
is the input data rate of each channel after de-interleaving.
COARSE MIXERS: CMIX0 AND CMIX1
The DAC5682Z has two coarse mixer (CMIX) blocks: CMIX0 follows FIR0 and CMIX1 follows FIR1. (See
Figure 32) Each CMIX block provides mixing capability of fixed frequencies Fs/2 (real) or ±Fs/4 (complex) with
respect to the output frequency of the preceding FIR block. Since FIR0 and CMIX0 are only used in x4
interpolation modes, the output is half-rate relative to the DAC output frequency. Therefore, an ±Fs/4 mixing
sequence results in ±F
DAC
/8 frequency shift at the DAC output.
Copyright © 2007–2012, Texas Instruments Incorporated Submit Documentation Feedback 33
Product Folder Links: DAC5682Z