AD7722 the analog and digital systems. Fast switching signals like clocks should be shielded with their associated ground to avoid radiating 14 AVDD1100nF noise to other sections of the board, and clock signals should 10 AGND1 never be routed near the analog inputs. 5V Avoid running digital lines under the device as these will couple 20 AVDD noise onto the die. The analog ground plane should be allowed 100nF10F100nF19 AGND to run under the AD7722 to shield it from noise coupling. The AV power supply lines to the AD7722 should use as large a trace as 23DD100nF possible (preferably a plane) to provide a low impedance path 25 AGND and reduce the effects of glitches on the power supply line. Avoid crossover of digital and analog signals. Traces on opposite 1039 DV sides of the board should run at right angles to each other. This DD1nF100nF10F100nF will reduce the effects of feedthrough through the board. 5DGND28 DGND Figure 29. Power Supply Decoupling –22– REV. B Document Outline FEATURES FUNCTIONAL BLOCK DIAGRAM GENERAL DESCRIPTION SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ORDERING GUIDE TIMING SPECIFICATIONS PIN FUNCTION DESCRIPTIONS PIN CONFIGURATION PARALLEL MODE PIN FUNCTION DESCRIPTIONS SERIAL MODE PIN FUNCTION DESCRIPTIONS TERMINOLOGY Signal-to-Noise Plus Distortion Ratio (S/(N+D)) Total Harmonic Distortion (THD) Spurious-Free Dynamic Range (SFDR) Intermodulation Distortion Pass-Band Ripple Pass-Band Frequency Cutoff Frequency Stop-Band Frequency Stop-Band Attenuation Integral Nonlinearity Differential Nonlinearity Common-Mode Rejection Ratio Unipolar Offset Error Bipolar Offset Error Gain Error Typical Performance Characteristics CIRCUIT DESCRIPTION APPLYING THE AD7722 Analog Input Range Differential Inputs Applying the Reference Input Circuits Clock Generation Varying the Master Clock SYSTEM SYNCHRONIZATION AND CONTROL SYNC Input DVAL Reset Input Power-On Reset Offset and Gain Calibration DATA INTERFACING Parallel Interface SERIAL INTERFACE 2-Channel Multiplexed Operation Serial Interfacing to DSPs OUTLINE DIMENSIONS Revision History