Datasheet AD7712 (Analog Devices) - 7

AD7712 TIMING CHARACTERISTICS (continued) Limit at TMIN, TMAX Parameter (A, S Versions) Unit Conditions/Comments
External Clocking Mode fSCLK fCLK IN/5 MHz max Serial Clock Input Frequency t20 0 ns min DRDY to RFS Setup Time t21 0 ns min DRDY to RFS Hold Time t22 2 ⫻ tCLK IN ns min A0 to RFS Setup Time t23 0 ns min A0 to RFS Hold Time t 7 24 4 ⫻ tCLK IN ns max Data Access Time (RFS Low to Data Valid) t 7 25 10 ns min SCLK Falling Edge to Data Valid Delay 2 ⫻ tCLK IN + 20 ns max t26 2 ⫻ tCLK IN ns min SCLK High Pulse Width t27 2 ⫻ tCLK IN ns min SCLK Low Pulse Width t28 tCLK IN + 10 ns max SCLK Falling Edge to DRDY High t 8 29 10 ns min SCLK to Data Valid Hold Time tCLK IN + 10 ns max t30 10 ns min RFS/TFS to SCLK Falling Edge Hold Time t 8 31 5 ⫻ tCLK IN/2 + 50 ns max RFS to Data Valid Hold Time t32 0 ns min A0 to TFS Setup Time t33 0 ns min A0 to TFS Hold Time t34 4 ⫻ tCLK IN ns min SCLK Falling Edge to TFS Hold Time t35 2 ⫻ tCLK IN – SCLK High ns min Data Valid to SCLK Setup Time t36 30 ns min Data Valid to SCLK Hold Time NOTES 8These numbers are derived from the measured time taken by the data output to change 0.5 V when loaded with the circuit of Figure 1. The measured number is then extrapolated back to remove effects of charging or discharging the 100 pF capacitor. This means that the times quoted in the timing characteristics are the true bus relinquish times of the part and, as such, are independent of external bus loading capacitances. Specifications subject to change without notice.
PIN CONFIGURATION DIP and SOIC SCLK 1 24 DGND 1.6mA MCLK IN 2 23 DVDD MCLK OUT 3 22 SDATA A0 4 21 DRDY TO OUTPUT 2.1V 5 20 SYNC RFS PIN AD7712 100pF MODE 6 TOP VIEW 19 TFS (Not to Scale) AIN1(+) 7 18 AGND AIN1(–) 8 17 AIN2 200
␮
A STANDBY 9 16 REF OUT TP 10 15 REF IN(+)
Figure 1. Load Circuit for Access Time and
V 11 14 SS REF IN(–)
Bus Relinquish Time
AV 12 13 DD VBIAS
–6– REV. F Document Outline ANALOG INPUT FUNCTIONS FEATURES APPLICATIONS GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAM PRODUCT HIGHLIGHTS SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ORDERING GUIDE TIMING CHARACTERISTICS PIN CONFIGURATION PIN FUNCTION DESCRIPTION TERMINOLOGY Integral Nonlinearity Positive Full-Scale Error Bipolar Zero Error Bipolar Negative Full-Scale Error Positive Full-Scale Overrange Negative Full-Scale Overrange Offset Calibration Range Full-Scale Calibration Range Input Span Control Register (24 Bits) Filter Selection (FS11–FS0) CIRCUIT DESCRIPTION THEORY OF OPERATION Input Sample Rate DIGITAL FILTERING Filter Characteristics Post Filtering Antialias Considerations ANALOG INPUT FUNCTIONS Analog Input Ranges Burnout Current Bipolar/Unipolar Inputs REFERENCE INPUT/OUTPUT VBIAS Input USING THE AD7712 SYSTEM DESIGN CONSIDERATIONS Clocking System Synchronization Accuracy Autocalibration Self-Calibration System Calibration System Offset Calibration Background Calibration Span and Offset Limits POWER-UP AND CALIBRATION Drift Considerations POWER SUPPLIES AND GROUNDING DIGITAL INTERFACE Self-Clocking Mode Read Operation Write Operation External Clocking Mode Read Operation Write Operation SIMPLIFYING THE EXTERNAL CLOCKING MODE INTERFACE MICROCOMPUTER/MICROPROCESSOR INTERFACING AD7712 to 8051 Interface AD7712 to 68HC11 Interface APPLICATIONS 4–20 mA LOOP OUTLINE DIMENSIONS Revision History