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DDS Wish List - Waveform Generator types - Not RF

Question asked by SouthPacific on Dec 16, 2010
Latest reply on Apr 19, 2011 by Alpha

This is a wish list for the Analog Devices lower frequency "Waveform Generator" type DDS - not the RF Type.


Reader comments from this list and all over the WEB lead me to wonder why Analog Devices isn't moving to more feature packed DDS chips - using the basic core?


My comments only relate to the DDS Function Generator type chips - which superseded the earlier generation Intersil ICL8038 type parts.


1) Add Sawtooth capability to the output – the current parts already have Sinewave (very useful) and Triangle (far less useful). Sawtooth waveforms are extremely difficult to create using the existing signals from these DDS parts.


2) Add Square capability to the output - as well. While the Sync Out is considered "Square", it still requires a lot of circuitry to get the Sync output to match the DDS's DAC's amplitude. Why can’t it come out of the output too?


3) Add the capability of Starting (or more specifically Setting) the output to a predefined 10-bit DC level (not DC Offset). To not only have Sine/Square/Triangle/Sawtooth waveforms would be good - but to also be able to set a DC output (using the Sawtooth map from 1) opens possibilities as well - even if it is only 10-bits of precision. These DDS parts already have a 10-bit DAC in the signal path - so it is just a matter of being able to write an address to the ROM - without the DDS actually cycling.


3) Ability to Sync multiple DDS together to get a phase shift between outputs. While not infinitely variable (more digital in nature), this becomes useful for 3-phase (120 degrees) and Quadrature (90 degrees) applications. Its appears to be available in a selection of RF parts.


6) Ability to set a Duty Cycle on the Square Wave - that I desire to come from the output.




I've often felt that an "analogue output" companion chip for the DDS could be useful. We are all purchasing the parts to create the "analogue output" section" from multiple vendors - so could AD consider producing a part like I describe below - which we can purchase from you?


1) SPI Controlled with an SPI Data Out that can cascade the serial data to the DDS IC.


2) An Attenuator like TI's PGA2311.


3) A +/- DC offset capability.


4) A command bit to set the output on or off.


5) One or two extra GPIO bits that can be used for a relay