Analog Devices AD911 Series User Manual page 11

Evaluation Board User Guide
Troubleshooting
This section lists items to check and practices to use when
debugging any unexpected performance of a board. It also
provides information on how to check for proper operation
when using the modulator in the signal chain.
If unexpected results occur
•
Reset the part (SW1) and rerun the SPI software.
•
Sync/reset the clock (SW2) when using the clock chip.
•
Check the voltage at TP30 (COREVDD), which should be
1.75 V.
•
Check the voltage at TP3 (VREF), which should be 1.0 V.
•
Probe S11 (DATACLK) to be sure that the DAC is properly
receiving data and that a clock signal is present. This signal
can also be probed at R64 near the part on-board (should
be unsoldered from initial setup instructions).
•
When using the modulator, check to make sure the common-
mode voltage is 0.5 V at the input of the modulator by probing
at R24 or R61 for the I or Q channels, respectively.
If the common-mode voltage is not as expected, unplug the
board and check the resistances at R13, R14, R52, and R53 for
the correct values of the particular board. If a proper reading is
not present, unsolder J13, J14, J19, and J23, which removes the
resistors from the parallel connection with 1 kΩ/100 Ω at the
input of the modulator to measure the individual resistances of
those components. Check if the resistance values are still
incorrect and if so, change out for the appropriate values listed
above. If not, try resoldering the jumpers and test again to make
sure there was not a problem with the previous connection.
Single Tone Test
In this example, a clock signal is sent to the board through the
clock distribution chip while data is input from the DPG2 and
observed at the DAC output. A 20 MHz single tone is created
and loaded through the DPGDownloader program and sent to
the board.
To create a single tone signal in the program
1. Select Add Generated Waveform and choose Single Tone
from the drop-down menu. An item then appears in the
downloader window.
2. Input the f
Desired Frequency. The DAC Resolution value is 14 bits,
Amplitude of 0dB and Record Length is 16384, as shown
in Figure 8.
3. Check the boxes next to Unsigned Data and Generate
Complex Data (I&Q).
4. In the I Data Vector and Q Data Vector drop-down
menus, choose the corresponding vectors from the list.
5. Press the download button (
the run button (
Figure 8. DPGDownloader
Rev. 0 | Page 11 of 12
as the Sample Rate and enter 20 MHz for
DAC
) and once completed, press
) to complete the load.
UG-073