Datasheet AD7621 (Analog Devices) - 10

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AD7621 Pin No. Mnemonic Type1 Description
32 CS DI Chip Select. When CS and RD are both low, the interface parallel or serial output bus is enabled. CS is also used to gate the external clock in slave serial mode. 33 RESET DI Reset Input. When high, reset the AD7621. Current conversion if any is aborted. Falling edge of RESET enables the calibration mode indicated by pulsing BUSY high. Refer to the Digital Interface section. If not used, this pin can be tied to DGND. 34 PD DI Power-Down Input. When high, power down the ADC. Power consumption is reduced and conversions are inhibited after the current one is completed. 35 CNVST DI Conversion Start. A falling edge on CNVST puts the internal sample-and-hold into the hold state and initiates a conversion. 36 AGND P Analog Power Ground Pin. 37 REF AI/O Reference Output/Input. When PDREF/PDBUF = low, the internal reference and buffer are enabled producing 2.048 V on this pin. When PDREF/PDBUF = high, the internal reference and buffer are disabled allowing an externally supplied voltage reference up to AVDD volts. Decoupling is required with or without the internal reference and buffer. Refer to the Voltage Reference Input section. 38 REFGND AI Reference Input Analog Ground. 39 IN− AI Differential Negative Analog Input. 43 IN+ AI Differential Positive Analog Input. 45 TEMP AO Temperature Sensor Analog Output. 46 REFBUFIN AI/O Internal Reference Output/Reference Buffer Input. When PDREF/PDBUF = low, the internal reference and buffer are enabled producing the 1.2 V (typical) bandgap output on this pin, which needs external decoupling. The internal fixed gain reference buffer uses this to produce 2.048V on the REF pin. When using an external reference with the internal reference buffer (PDBUF = low, PDREF = high), applying 1.2 V on this pin produces 2.048 V on the REF pin. Refer to the Voltage Reference Input section. 47 PDREF DI Internal Reference Power-Down Input. When low, the internal reference is enabled. When high, the internal reference is powered down and an external reference must been used. 48 PDBUF DI Internal Reference Buffer Power-Down Input. When low, the buffer is enabled (must be low when using internal reference). When high, the buffer is powered-down. 1 AI = analog input; AI/O = bidirectional analog; AO = analog output; DI = digital input; DI/O = bidirectional digital; DO = digital output; P = power. Rev. 0 | Page 10 of 32 Document Outline FEATURES APPLICATIONS GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAM PRODUCT HIGHLIGHTS SPECIFICATIONS TIMING SPECIFICATIONS SERIAL CLOCK TIMING SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TERMINOLOGY TYPICAL PERFORMANCE CHARACTERISTICS THEORY OF OPERATION CIRCUIT INFORMATION CONVERTER OPERATION MODES OF OPERATION TRANSFER FUNCTIONS TYPICAL CONNECTION DIAGRAM ANALOG INPUTS DRIVER AMPLIFIER CHOICE Single-to-Differential Driver VOLTAGE REFERENCE INPUT Internal Reference External 1.2 V Reference and Internal Buffer External Reference Reference Decoupling Temperature Sensor POWER SUPPLY Power Sequencing Power-Up POWER DISSIPATION VS. THROUGHPUT CONVERSION CONTROL INTERFACES DIGITAL INTERFACE RESET PARALLEL INTERFACE Master Parallel Interface Slave Parallel Interface 8-Bit Interface (Master or Slave) SERIAL INTERFACE MASTER SERIAL INTERFACE Internal Clock SLAVE SERIAL INTERFACE External Clock External Discontinuous Clock Data Read After Conversion External Clock Data Read During Previous Conversion MICROPROCESSOR INTERFACING SPI Interface (ADSP-219x) APPLICATION LAYOUT EVALUATING THE AD7621 PERFORMANCE OUTLINE DIMENSIONS ORDERING GUIDE