AD9144BCPZ datasheet(80/125 Pages) AD

80 / 125 page

AD9144

Data Sheet

Rev. B | Page 80 of 125

Powering Down Unused DACs

Power down any unused DAC outputs to avoid burning excess

power. The DAC power downs are located in Register 0x011.

DAC1, Bit 4 corresponds to DAC2, and Bit 3 corresponds to DAC3.

Write a 1 to each bit to power down the appropriate DACs.

gap and DAC master bias, respectively.

For more information on which DACs to power down, see the

DAC Power-Down Setup section.

Self Calibration

The AD9144 has a self calibration feature that improves the

DAC dc and ac linearity in zero or low IF applications. The

performance improvement includes the INL/DNL, second and

fourth harmonic distortions (HD2 and HD4), and second-order

intermodulation distortion (IMD2) of the device. Figure 82 and

Figure 83 show the typical DAC INL and DNL before and after

the calibration. Figure 84 and Figure 85 show the calibration effect

on the HD2, HD4, and IMD2 performance. The improvement

from calibration decreases with the DAC output frequency. For

improvement in HD2 and HD4, it is recommended to run the

calibration routine when the desired output frequency is below

100 MHz. For improvement in IMD2, it is recommended to run

the routine when the desired output frequency is below 200 MHz.

A single run of the routine is sufficient to obtain the desired

performance for both ac and dc performance.

–4

–3

–2

–1

70k

60k

50k

40k

30k

20k

10k

DAC GAIN CODE

CALIBRATION OFF

CALIBRATION ON

Figure 82. Pre-Calibration and Post-Calibration, INL

–2

–1

70k

60k

50k

40k

30k

20k

10k

DAC GAIN CODE

CALIBRATION OFF

CALIBRATION ON

Figure 83. Pre-Calibration and Post-Calibration, DNL

–40

–100

–90

–80

–70

–60

–50

300

250

200

150

100

fOUT (MHz)

CALIBRATION OFF

CALIBRATION ON

SECOND HARMONIC

FOURTH HARMONIC

Figure 84. Pre-Calibration and Post-Calibration, HD2 and HD4

–60

–65

–70

–75

–80

–85

–90

–95

–100

300

250

200

150

100

fOUT (MHz)

CALIBRATION OFF

CALIBRATION ON

Figure 85. Pre-Calibration and Post-Calibration, IMD2

AD9144BCPZ Datasheet(PDF) 80 Page - Analog Devices

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