DAC5687IPZP datasheet(20/79 Pages) TI

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Peak-to-Average Ratio − dB

G041

10−6

1 Carrier

2 Carriers

4 Carriers

10−4

10−2

100

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 FMIX

–

X2 QMC

–

X2 FMIX QMC

–

X2 CMIX

–

X2 FMIX CMIX

–

X2 QMC CMIX

–

ON(1)

X2 FMIX QMC CMIX

–

ON(1)

–

X4 FMIX(2)

–

X4 QMC(2)

–

X4 FMIX QMC

–

X4 CMIX

–

X4L

–

(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)

fDAC limited to maximum clock rate for the NCO and QMC (see Electrical Characteristics (AC

Specifications)).

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