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Introduced nearly a decade ago, Analog Devices Inc.'s high-speed TxDAC family has added fourth-generation members with improved performance and pin compatibility with previous generations. Implemented in 0.18 µm CMOS, AD9707/6/5/4 are 14-bit, 12-bit, 10-bit and 8-bit resolution, 175 Msps, low-power fourth-generation members of TxDAC series. The dimensions of performance optimized in this family are power consumption and ease of use. While prior best in class spurious-free dynamic range (SFDR) and intermodulation distortion (IMD) performance of third-generation AD974x were retained, the new-generation DACs minimize power consumption and maximize analog functionality. In fact, it lowers power consumption by half that of competing parts at equivalent operating conditions. Likewise, by comparison to older parts in the family, the power consumption of new members is one-quarter at 3.3 V and one-tenth at 1.8 V.

Hence, typical power consumption at maximum sample rate for the 14-bit part AD9707 is 55 mW at 3.3 V and 2 mA full-scale output current. With a slight degradation in performance, its power dissipation can be further reduced to 15 mW by lowering the full-scale current output. Also, a power-down mode reduces the standby power dissipation to approximately 5 mW. The AD9707's flexible power supply operating range of 1.7 V to 3.6 V and low power dissipation makes it well suited for portable and low-power applications.

Plus, the new transmit signal path DACs offer feature-rich analog output, which includes common mode shift capability to ease interfacing with other components that require common modes greater than 0 V. Adjustable output common mode is from 0 V to 1.2 V.

Furthermore, the fourth-generation DACs include on-chip set and load resistors to minimize bill of material cost. These resistors are adjustable. For instance, the set resistor is adjustable from 8 k to 32 kΩ with 6-bit resolution, while load resistor can be varied from 250 Ω to 2 kΩ.

Edge-triggered input latches and 1.0 V temperature-compensated band gap reference have been integrated to provide a complete monolithic solution (see the figure). The units come in 28-lead TSSOP and 32-lead LFCSP packages. Because all of the devices share the same interface, small outline package, and pin-out, they provide an upward or downward component selection path based on performance, resolution and cost. The AD9707-LFCSP has an optional serial peripheral interface (SPI), which provides a higher level of programmability.

A DAC evaluation board comes with pattern generator that provides high-speed digital data to ADI's DACs. It supports CMOS and LVDS data formats, and offers 512 Mbytes of RAM for complex waveform generation.

Pricing for the family ranges from $2.75 to $5.75 in 1000-unit quantities, depending on resolution.

Analog Devices Inc.
Wilmington, MA
(800) 262-5643
www.analog.com

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