AnsweredAssumed Answered

How to power up an AD9854PCBZ evaluation board

Question asked by pacojavisanz on Nov 15, 2010
Latest reply on Jun 9, 2013 by Skfir

I've been working with some AD9854PCBz evaluation boards on the laboratory for a while, but now I am integrating these boards on a specific design, an I have facing some problems in powering the unit.

Until now, I used an external power supply unit to feed the evaluation board, connecting the three voltage inputs of the board (Vdd, Avdd and Dvdd) to 3.3V and grounding the board. With this set up depending on the multiplier set on the DDS the input frequency of the reference and the gain and output frequencies programmed, the consumption read at the power supply can vary from 0.2 to 1.3A.

Then I used a linear regulator LT1086CT up to 1.5A to feed the evaluation board, and I observed a strange behaviour of the evaluation board. The programmed frequency varies a lot, sometimes I saw jumps in the output frequency as well as several spurious signals running around the main carrier output.

After some time I started the board and switched it off, I realized that the board stopped working. The application software provided by Analog detects the connection with the board through the parallel port, but the board does not provide any output. If I connected this board to the initial external power supply, then the board seems to be shortcircuited, and everytime the board is powered up, the power supply unit cut the current to the limited set value (i.e 1.5A or 2).

This has happened with two different boards, and I don't want to continue testing, without knowing where the problem is. Is there any peak currents when connecting the AD9854 evaluation board? Is there any Application note where I can find recommendations for powering these boards? Is there any recommended specific power supply for these boards?

I have checked the output of the voltage regulator (3.3V), I have checked the jumpers configuration according to the datasheet as well, and I am thinking on installing a fuse to protect the board in case of a peak at the start up.

Any ideas?

Thanks for your support.