Datasheet AD7934-6 (Analog Devices) - 9

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AD7934-6 Pin No. Mnemonic Description
22 CS Chip Select. Active low logic input used in conjunction with RD and WR to read conversion data or write data to the control register. 23 AGND Analog Ground. This is the ground reference point for all analog circuitry on the AD7934-6. All analog input signals and any external reference signal should be referred to this AGND voltage. The AGND and DGND voltages should ideally be at the same potential and must not be more than 0.3 V apart, even on a transient basis. 24 VREFIN/VREFOUT Reference Input/Output. This pin is connected to the internal reference, and is the reference source for the ADC. The nominal internal reference voltage is 2.5 V, and it appears at this pin. It is recommended that this pin be decoupled to AGND with a 470 nF capacitor. This pin can be overdriven by an external reference. The input voltage range for the external reference is 0.1 V to VDD; however, care must be taken to ensure that the analog input range does not exceed VDD + 0.3 V. See the Reference section. 25 to 28 VIN0 to VIN3 Analog Input 0 to Analog Input 3. Four analog input channels that are multiplexed into the on-chip track-and- hold. The analog inputs can be programmed to be four single-ended inputs, two fully differential pairs, or two pseudo differential pairs by setting the MODE bits in the control register appropriately (see Table 9). The analog input channel to be converted can be selected either by writing to the address bits (ADD1 and ADD0) in the control register prior to the conversion, or by using the on-chip sequencer. The input range for all input channels can be either 0 V to VREF, or 0 V to 2 × VREF, and the coding can be binary or twos complement, depending on the states of the RANGE and CODING bits in the control register. Any unused input channels should be connected to AGND to avoid noise pickup. Rev. B | Page 8 of 28 Document Outline FEATURES FUNCTIONAL BLOCK DIAGRAM GENERAL DESCRIPTION PRODUCT HIGHLIGHTS REVISION HISTORY SPECIFICATIONS TIMING SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS TERMINOLOGY CONTROL REGISTER SEQUENCER OPERATION Writing to the Control Register to Program the Sequencer CIRCUIT INFORMATION CONVERTER OPERATION ADC TRANSFER FUNCTION TYPICAL CONNECTION DIAGRAM ANALOG INPUT STRUCTURE ANALOG INPUT CONFIGURATIONS Single-Ended Mode Differential Mode Driving Differential Inputs Using an Op Amp Pair Pseudo Differential Mode ANALOG INPUT SELECTION Traditional Multichannel Operation (SEQ0 = SEQ1 = 0) Using the Sequencer: Consecutive Sequence (SEQ0 = SEQ1 = 1) REFERENCE Digital Inputs VDRIVE Input PARALLEL INTERFACE Reading Data from the AD7934-6 Writing Data to the AD7934-6 POWER MODES OF OPERATION Normal Mode (PM1 = PM0 = 0) Autoshutdown Mode (PM1 = 0; PM0 = 1) Autostandby Mode (PM1 = 1; PM0 = 0) Full Shutdown Mode (PM1 = 1; PM0 = 1) POWER vs. THROUGHPUT RATE MICROPROCESSOR INTERFACING AD7934-6 to ADSP-21xx Interface AD7934-6 to ADSP-21065L Interface AD7934-6 to TMS32020, TMS320C25, and TMS320C5x Interface AD7934-6 to 80C186 Interface APPLICATION HINTS GROUNDING AND LAYOUT EVALUATING THE AD7934-6 PERFORMANCE OUTLINE DIMENSIONS ORDERING GUIDE