Datasheet

www.ti.com
Peak-to-Average Ratio − dB
3 5 7 9 11 13 15
Cummulative Complementary Distribution Function
G041
10
−6
1 Carrier
2 Carriers
4 Carriers
10
−4
10
−2
10
0
DETAILED DESCRIPTION
Modes of Operation
DAC5687
SLWS164E – FEBRUARY 2005 – REVISED SEPTEMBER 2006
Figure 28. WCDMA TM1 Cumulative Complementary Distribution Function for 1, 2, and 4 Carriers
The DAC5687 has six digital signal processing blocks: FIR1 and FIR2 (interpolate-by-two digital filters), FMIX
(fine frequency mixer), QMC (quadrature modulation phase correction), FIR3 (interpolate-by-two digital filter) and
CMIX (coarse frequency mixer). The modes of operation, listed in Table 1 , enable or bypass the blocks to
produce different results. The modes are selected by registers CONFIG1, CONFIG2, and CONFIG3 (0x02, 0x03,
and 0x04). Block diagrams for each mode (X2, X4, X4L, and X8) are shown in Figure 29 through Figure 32 .
Table 1. DAC5687 Modes of Operation
MODE FIR1 FIR2 FMIX QMC FIR3 CMIX
FULL BYPASS – – – – – –
X2 – – – – ON –
X2 FMIX – – ON – ON –
X2 QMC – – – ON ON –
X2 FMIX QMC – – ON ON ON –
X2 CMIX – – – – ON ON
X2 FMIX CMIX – – ON – ON ON
X2 QMC CMIX – – – ON
(1)
ON ON
X2 FMIX QMC CMIX – – ON ON
(1)
ON ON
X4 ON ON – – – –
X4 FMIX
(2)
ON ON ON – – –
X4 QMC
(2)
ON ON – ON – –
X4 FMIX QMC ON ON ON ON – –
X4 CMIX ON ON – – – ON
X4L ON – – – ON –
(1) The QMC phase correction is eliminated by the CMIX, so the QMC phase should be set to zero. The
QMC gain settings can still be used to adjust the signal path gain as needed.
(2) f
DAC
limited to maximum clock rate for the NCO and QMC (see Electrical Characteristics (AC
Specifications) ).
20 Submit Documentation Feedback Copyright © 2005 – 2006, Texas Instruments Incorporated
Product Folder Link(s): DAC5687