Choosing DAC for Digital Inkjet Printer

Siva,

Our Precision DAC Products are usually intended for DC applications and as such the datasheet specifications are really targeted to provide useful information for these applications. Unfortunately there isn't so much information about AC applications using Precision DACs, partly because it's not our primary application space and partly because there are so many variables to consider that it would be very difficult to describe in the datasheet while still being flexible enough for customers to tailor to their own application needs.

With that said, one of the first-order items to consider is settling time. Settling time for DACs is usually provided for a nearly full-scale step size with the outputs settled within a 1 LSB error-band. Generally speaking the fastest Precision DAC products unbuffered voltage-output R-2R DACs or unbuffered current-output MDACs and the fastest speeds you can realize (based on the full-scale 1-LSB settling time specification) is 0.5us to 1us or 1-2MHz update rate. This will dictate the number of updates per sinusoid period and influence the THD or SNR of the sinusoid.

Since you will be using smaller step-sizes than a full-scale step for most of, if not all of, the points that make up the sinusoid you may find that the settling time figure is not actually the bottle-neck, but is instead the through-put of the digital interface. In such a case it may be beneficial to look at DACs that feature parallel interfaces since these will allow you to latch data into the DAC data register faster and eliminate the digital through-put as an obstacle.

Other factors to consider would be the amplitude of the sinusoid and exactly how "precise" you need the outputs to be. Predominantly a device with lower gain error and INL error will help maintain better AC performance. You may also consider some level of filtering or attenuation on the digital edges (if possible based on digital through-put requirements) as they relate to digital feedthrough, as this will also decay AC performance.