Datasheet AD7981 (Analog Devices) - 7

Data Sheet AD7981 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS REF 1 10 VIO REF 1 10 VIO VDD 2 9 SDI VDD 2 9 SDI AD7981 AD7981 IN+ 3 8 SCK TOP VIEW IN+ 3 TOP VIEW 8 SCK IN– (Not to Scale) 4 7 SDO (Not to Scale) IN– 4 7 SDO
004
GND 5 6 CNV
005
GND 5 6 CNV
12479- 12479- Figure 4. 10-Lead MSOP Pin Configuration Figure 5. 10-Lead FLATPACK Pin Configuration
Table 5. Pin Function Descriptions Pin No. Mnemonic Type1 Description
1 REF AI Reference Input Voltage. The REF range, VREF, is from 2.4 V to 5.1 V. VREF is referred to the GND pin. Decouple REF with a 10 μF capacitor as close as possible to the pin. 2 VDD P Power Supply. 3 IN+ AI Analog Input. This pin is referred to IN−. The voltage range, for example, the difference between IN+ and IN−, is 0 V to VREF. 4 IN− AI Analog Input Ground Sense. Connect this pin to the analog ground plane or to a remote sense ground. 5 GND P Power Supply Ground. 6 CNV DI Conversion Input. This input has multiple functions. On its leading edge, it initiates the conversions and selects the interface mode of the device: chain or CS mode. In CS mode, it enables the SDO pin when low. In chain mode, read the data when CNV is high. 7 SDO DO Serial Data Output. The conversion result is output on this pin. It is synchronized to SCK. 8 SCK DI Serial Data Clock Input. When the device is selected, the conversion result is shifted out by this clock. 9 SDI DI Serial Data Input. This input provides multiple features. It selects the interface mode of the ADC as follows: Chain mode is selected if SDI is low during the CNV rising edge. In this mode, SDI is used as a data input to daisy-chain the conversion results of two or more ADCs onto a single SDO line. The digital data level on SDI is output on SDO with a delay of 16 SCK cycles. CS mode is selected if SDI is high during the CNV rising edge. In this mode, either SDI or CNV can enable the serial output signals when low. If SDI or CNV is low when the conversion is complete, the busy indicator feature is enabled. 10 VIO P Input/Output Interface Digital Power. VIO is nominally at the same supply as the host interface (1.8 V, 2.5 V, 3 V, or 5 V). 1AI is the analog input, P is the power, DI is the digital input, and DO is the digital output. Rev. B | Page 7 of 26 Document Outline FEATURES APPLICATIONS TYPICAL APPLICATION CIRCUIT GENERAL DESCRIPTION REVISION HISTORY SPECIFICATIONS TIMING SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS TERMINOLOGY THEORY OF OPERATION CIRCUIT INFORMATION CONVERTER OPERATION Transfer Functions TYPICAL CONNECTION DIAGRAM ANALOG INPUT DRIVER AMPLIFIER CHOICE VOLTAGE REFERENCE INPUT POWER SUPPLY DIGITAL INTERFACE \CS MODE, 3-WIRE WITHOUT A BUSY INDICATOR \CS MODE, 3-WIRE WITH A BUSY INDICATOR \CS MODE, 4-WIRE WITHOUT A BUSY INDICATOR \CS MODE, 4-WIRE WITH A BUSY INDICATOR CHAIN MODE WITHOUT A BUSY INDICATOR CHAIN MODE WITH A BUSY INDICATOR APPLICATIONS INFORMATION PRINTED CIRCUIT BOARD (PCB) LAYOUT OUTLINE DIMENSIONS ORDERING GUIDE