Digital to analog converters usually come with one or two channels. Sadly, analog output needs tend to flock – in that case, Analog Device’s eight-converter AD534x family is an excellent contender.
As with most DACs, the functional block diagram provides a general overview of the internal structure and makes for a great starting point. In case of the AD534x family, the chart looks like figure 1.
Eight DACs lead to the presence of a large amount of glue logic
Fortunately, the internal structure is simple. The part is a parallel input DAC, which means that a total of eight, ten or twelve data lines are needed to provide the entire set of output information. Address lines allow the selection of individual output buffers, thereby permitting targeted changing of individual DAC outputs.
Analog Devices AD534x series differs from other converters due to the sophisticated control scheme. In addition to the normal write control and chip select pins, a dedicated pin named LDAC allows you to get data into DAC registers.
In addition to that, that CLR pin provides a simple way to clean a register, while the RD pin allows you get data back from the DAC. This feature might not sound very useful at first glance – when dealing with micro-controllers with limited memory, being able to off-load a few bytes may spare you from having to switch to a larger model.
The architecture of the part does not allow for high speeds. Analog Devices claims that a write to one channel can be handled in 20 nanoseconds – this is not particularly fast, which means that you shouldn’t use the part for your next arbitrary waveform generator.
On the other hand, excellent stability values of both 8-, 10- and 12bit parts predestine the family for applications where controlled voltages are required – think variable gain amplifiers, biased sources or various parameters controlling an attenuator.
For prototyping, the situation is a mixed bag. AD provides the part in TSSOP and LFCSP housings – the first challenges hand solderers with a pin spacing of less than 0.65 mm. For pricing, the table shows the current oemsecrets price.
Analog Devices deserves a special mention for the excellent data sheet. It contains valuable resources on both basics and application circuits – if you are not a seasoned pro in working ADCs, definitely take a look.