AD9708:  8-Bit, 100 MSPS+ TxDAC® D/A Converter

The AD9708 is the 8-bit resolution member of the TxDAC™ series of high performance, low power CMOS digital-to-analog converters (DACs). The TxDAC™ family, which consists of pin compatible 8-, 10-, 12-, and 14-bit DACs, was specifically optimized for the transmit signal path of communication systems. All of the devices share the same interface options, small outline package and pinout, thus providing an upward or downward component selection path based on performance, resolution and cost. The AD9708 offers exceptional ac and dc performance while supporting update rates up to 125 MSPS.

The AD9708's flexible single-supply operating range of 2.7 V to 5.5 V and low power dissipation are well suited for portable and low power applications. Its power dissipation can be further reduced to 45 mW, without a significant degradation in performance, by lowering the full-scale current output. In addition, a power-down mode reduces the standby power dissipation to approximately 20 mW.

The AD9708 is manufactured on an advanced CMOS process. A segmented current source architecture is combined with a proprietary switching technique to reduce spurious components and enhance dynamic performance. Edge-triggered input latches and a temperature compensated bandgap reference have been integrated to provide a complete monolithic DAC solution. Flexible supply options support +3 V and +5 V CMOS logic families.

The AD9708 is a current-output DAC with a nominal full-scale output current of 20 mA and > 100 k Ohms output impedance.

Differential current outputs are provided to support single-ended or differential applications. The current outputs may be directly tied to an output resistor to provide two complementary, single-ended voltage outputs. The output voltage compliance range is 1.25 V.

The AD9708 contains a 1.2 V on-chip reference and reference control amplifier, which allows the full-scale output current to be simply set by a single resistor. The AD9708 can be driven by a variety of external reference voltages. The AD9708's full-scale current can be adjusted over a 2 mA to 20 mA range without any degradation in dynamic performance. Thus, the AD9708 may operate at reduced power levels or be adjusted over a 20 dB range to provide additional gain ranging capabilities.

The AD9708 is available in a 28-pin SOIC package. It is specified for operation over the industrial temperature range.