How to read a DAC data sheet?

[waspinator]

I'm want to try to make a simple arbitrary waveform generator as a project to learn more about electronics.

I'm thinking of using a DAC controlled by a micro controller, but I'm not sure what to look for. For example when I look at the specs for a real AWG I always see the maximum frequency of a sin wave mentioned, but I'm not sure how I would translate that into a spec on a DAC datasheet.

What are the most important specs to look for in a DAC for a project like this?

Thanks

Example DAC datasheet:
datasheets.maximintegrated.com/en/ds/MAX541-MAX542.pdf

[suicidaleggroll]

Well the biggest one with that device is going to be the serial clock.  It runs at 10 MHz and requires 16 bits of data plus a CS cycle to latch it.  So you're looking at around 18 clock cycles minimum per value.  At 10 MHz, that means you can send the DAC one value every 1.8uS.  It would take two values to make a square wave, so your fastest square wave could be ~275 kHz, but it's not going to be very clean and you're not going to have good frequency control up there.  Realistically I'd say you'd be limited to ~25 kHz max, if you can handle only having ~10 discrete points per period in your wave (anything other than a square wave is going to be pretty ugly without some filtering).

16 bit doesn't buy you much for that application, it just takes too long to get the data into the DAC to be of much use for high frequencies.  You'd be much better off with a DAC that has less resolution and a faster clock (even half the resolution with the same clock would buy you double the frequency range since you'd be able to clock in your values twice as fast).

Think about it this way.  16 bit has 65536 possible values.  At 18 clock cycles per value and a 10 MHz clock, it would take you over 100ms just to sweep through the DAC's range once, in one direction.

Setting time matters as well, but for that device in that application, the limiting factor is going to be how quickly you can pump the data into the DAC over that serial line.

[dannyf]

What are the most important specs to look for in a DAC for a project like this?

At a high level, you are going to look for a few things:

1) parallel vs. serial: parallel interface is generally faster but takes lots of pins; serial interface as a result is more common;
2) interface protocol: parallel is simple; for serial dac, you need to know if it is i2c, spi, or other forms. spi or i2s is typically the fastest;
3) output type: current output (fastest) vs. voltage output;
4) differential output vs. singled ended;
5) resolution - in terms of bits;
6) supply voltage;
7) buffered output vs. non-buffered output;
output swing;
9) internal ref vs. external ref;
...