Analog Devices, Inc. introduced the 8-bit AD7304 and AD7305, a new generation of quad voltage-output DACs designed for general-purpose dc and ac gain, with offset adjustment in new system designs where cost, low power consumption, and a small footprint are the design criteria. These new DACs bring performance, price and size advantages to systems ranging from medical diagnostic, portable and automatic test equipment, to automatic factory test system calibration and to telecommunications systems.

The AD7304 and AD7305 operate from a single +3 to +5-V supply or ý5-V supplies, guaranteed over the supply voltage range of +2.7, or +5.5 to ý5 V. These DACs feature a true rail-to-rail V_REF-input to voltage-output swing, with a reference input range that includes both supply rails, allowing for positive or negative full-scale output voltages with a reference multiplying-bandwidth of 2.6 MHz.

An internal power ON reset places both parts in the zero-scale state at turn ON. A unique 40 ýA power shutdown (SHDN) feature is activated on both parts by three-stating the SDI/SHDN pin on the AD7304, and three-stating the A0/SHDN address pin on the AD7305. The AD7304/AD7305 are specified over the extended industrial (-40 to +85ýC), and the automotive (-40 to +125ýC) temperature ranges.

The AD7304's double-buffered serial-data interface offers high-speed, three-wire, SPI and microcontroller compatible inputs using data in (SDI), clock (CLK) and chip select (CS) pins. The parallel input AD7305 uses a standard address decode along with the WR control line to load data into the input registers. The double-buffered architecture allows all four input registers to be preloaded with new values followed by a LDAC control strobe that copies all the new data into the DAC registers, thereby updating the analog output values simultaneously. The AD7305 is pin-compatible with the popular industry-standard AD7226 when operating from less than +5.5 V.

Commodity parts are us. These two products meet a large spectrum of users' needs for 8-bit parts and, additionally, add four channel capability all at a commodity price. It is a major sign of the times as we roll into the next generation of data-acquisition parts; when you add into the equation the small footprints available and the low power consumption you will probably have to reconsider some previous design decisions you made using non-CMOS products, and even earlier CMOS-processed parts. Any further down this path, in fact, is going to endanger at least the profit margins of some of the analog vendors who have strayed, or deliberately stayed behind in their process technologies. There will always continue to be markets for specialized niche (and expensive, therefore profitable) parts from these vendors, but more and more you are going to hear the retort from them, "We have no commodity parts" -- well, maybe not from the marketing departments.

I love the wide choice of supply rails, the rail-to-rail performance and the power shutdown feature -- essential for design of parts into portable products. The availability of the higher automotive temperature range will additionally widen the markets that these parts can address, which is already very wide anyway. The ability to update all the analog outputs simultaneously will also simplify a number of ATE and telecommunication systems designs.

The 16-pin AD7304 and 20-pin AD7305 are available in PDIP, SOL and TSSOP, and are priced at $3.25 and $3.75, respectively, in 1000-piece lots. Both are in production.