AD9768

a FEATURES 5 ns Settling Time 100 MSPS Update Rate 20 mA Output Current ECL-Compatible 40 MHz Multiplying Mode APPLICATIONS Raster Scan & Vector Graphic Displays High Speed Waveform Generation Digital VCOs Ultrafast Digital Attenuators GENERAL DESCRIPTION Ultrahigh Speed IC D/A Converter AD9768 FUNCTIONAL BLOCK DIAGRAM The Analog Devices AD9768SD D/A converter is a monolithic current-output converter which can accept 8 bits of ECL-level digital input voltages and convert them into analog signals at update rates as high as 100 MSPS. In addition to its use as a standard D/A converter, it can also be utilized as a two-quadrant multiplying D/A at multiplying bandwidths as high as 40 MHz. An inherently low glitch design is used, and the complementary current outputs are suitable for driving transmission lines directly. Nominal full-scale output is 20 mA, which corresponds to a 1 volt drop across a 50 Ω load, or ± 1 volt across 100 Ω returned to +1 volt. The actual output current is determined by the on-chip reference voltage (VREF Ϸ –1.26 V) and an external current setting resistor, RSET. Full-scale output current IOUT with digital “1” at all inputs is calculated with the equation: The reference voltage source is a modified bandgap type and is nominally –1.26 volts. This reference supply requires no external regulation. To reduce the possibility of noise generation and/or instability, Pin 15 (REFERENCE OUT) can be decoupled using a high-quality ceramic chip capacitor. Stabiliza...