Datasheet AD7656A (Analog Devices) - 9

AD7656A Data Sheet Pin No. Mnemonic Description
10 DB7/HBEN/DCEN Data Bit 7/High Byte Enable/Daisy-Chain Enable. When operating in parallel word mode (SER/PAR/SEL = 0 and W/B = 0), Pin 10 takes on its Data Bit 7 function. When operating in parallel byte mode (SER/PAR/SEL = 0 and W/B = 1), Pin 10 takes on its HBEN function. When in this mode and the HBEN pin is logic high, the data is output MSB byte first on DB15 to DB8. When the HBEN pin is logic low, the data is output LSB byte first on DB15 to DB8. When operating in serial mode (SER/PAR/SEL = 1), Pin 10 takes on its DCEN function. When the DCEN pin is logic high, the AD7656A operates in daisy- chain mode with DB5 to DB3 taking on their DCIN A to DCIN C function. When operating in serial mode but not in daisy-chain mode, tie DCEN to DGND. 11 DB6/SCLK Data Bit 6/Serial Clock. When SER/PAR/SEL = 0, this pin acts as a three-state paral el digital output pin. When SER/PAR/SEL = 1, this pin takes on its SCLK input function; it is the read serial clock for the serial transfer. 12 DB5/DCIN A Data Bit 5/Daisy-Chain Input A. When SER/PAR/SEL is low, this pin acts as a three-state parallel digital output pin. When SER/PAR SEL = 1 and DCEN = 1, this pin acts as Daisy-Chain Input A. When operating in serial mode but not in daisy-chain mode, tie this pin to DGND. 13 DB4/DCIN B Data Bit 4/Daisy-Chain Input B. When SER/PAR/SEL = 0, this pin acts as a three-state parallel digital output pin. When SER/PAR/SEL = 1 and DCEN = 1, this pin acts as Daisy-Chain Input B. When operating in serial mode but not in daisy-chain mode, tie this pin to DGND. 14 DB3/DCIN C Data Bit 3/Daisy-Chain Input C. When SER/PAR/SEL = 0, this pin acts as a three-state parallel digital output pin. When SER/PAR/SEL = 1 and DCEN = 1, this pin acts as Daisy-Chain Input C. When operating in serial mode but not in daisy-chain mode, tie this pin to DGND. 15 DB2/SEL C Data Bit 2/Select DOUT C. When SER/PAR/SEL = 0, this pin acts as a three-state parallel digital output pin. When SER/PAR/SEL = 1, this pin takes on its SEL C function; it is used to configure the serial interface. If this pin is 1, the serial interface operates with three DOUT output pins and enables DOUT C as a serial output. If this pin is 0, the DOUT C is not enabled to operate as a serial data output pin. Leave unused serial DOUT pins unconnected. 16 DB1/SEL B Data Bit 1/Select DOUT B. When SER/PAR/SEL = 0, this pin acts as a three-state parallel digital output pin. When SER/PAR/SEL = 1, this pin takes on its SEL B function; it is used to configure the serial interface. If this pin is 1, the serial interface operates with two or three DOUT x output pins and enables DOUT B as a serial output. If this pin is 0, the DOUT B is not enabled to operate as a serial data output pin and only one DOUT output pin, DOUT A, is used. Leave unused serial DOUT pins unconnected. 17 DB0/SEL A Data Bit 0/Select DOUT A. When SER/PAR/SEL = 0, this pin acts as a three-state parallel digital output pin. When SER/PAR/SEL = 1, Pin 17 takes on its SEL A function; it is used to configure the serial interface. If this pin is 1, the serial interface operates with one, two, or three DOUT x output pins and enables DOUT A as a serial output. When operating in serial mode, this pin must always be 1. 18 BUSY Busy Output. This pin transitions high when a conversion is started and remains high until the conversion is complete and the conversion data is latched into the output data registers. Do not initiate a new conversion on the AD7656A when the BUSY signal is high. 19 CS Chip Select. This active low logic input frames the data transfer. When both CS and RD are logic low in parallel mode, the output bus is enabled and the conversion result is output on the parallel data bus lines. When both CS and WR are logic low in parallel mode, DB15 to DB8 are used to write data to the on-chip control register. In serial mode, the CS is used to frame the serial read transfer and clock out the MSB of the serial output data. 20 RD Read Data. When both CS and RD are logic low in parallel mode, the output bus is enabled. In serial mode, hold the RD line low. 21, 22, 23 CONVST C, Conversion Start Input C, Conversion Start Input B, and Conversion Start Input A. These logic inputs CONVST B, are used to initiate conversions on the ADC pairs. CONVST A is used to initiate simultaneous conversions CONVST A on V1 and V2, CONVST B is used to initiate simultaneous conversions on V3 and V4, and CONVST C is used to initiate simultaneous conversions on V5 and V6. When CONVST x switches from low to high, the track-and-hold switch on the selected ADC pair switches from track to hold, and the conversion is initiated. These inputs can also be used to place the ADC pairs into partial power-down mode. 24 STBY Standby Mode Input. This pin is used to put all six on-chip ADCs into standby mode. The STBY pin is high for normal operation and low for standby operation. 26 DVCC Digital Power, 4.75 V to 5.25 V. Ideally, the DVCC and AVCC voltages are at the same potential and must not be more than 0.3 V apart, even on a transient basis. Decouple this supply to DGND, and place 10 µF and 100 nF decoupling capacitors on the DVCC pin. Rev. 0 | Page 8 of 28 Document Outline FEATURES APPLICATIONS FUNCTIONAL BLOCK DIAGRAM GENERAL DESCRIPTION PRODUCT HIGHLIGHTS TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS TIMING SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS POWER SUPPLY SEQUENCING THERMAL RESISTANCE ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS TERMINOLOGY THEORY OF OPERATION CONVERTER DETAILS Track-and-Hold Amplifiers Analog Input ADC TRANSFER FUNCTION REFERENCE SECTION TYPICAL CONNECTION DIAGRAM DRIVING THE ANALOG INPUTS INTERFACE SECTION Parallel Interface (SER/PAR/SEL = 0) SOFTWARE SELECTION OF ADCS Changing the Analog Input Range (H/S SEL = 0) Changing the Analog Input Range (H/S SEL = 1) Serial Interface (SER/PAR/SEL = 1) SERIAL READ OPERATION DAISY-CHAIN MODE (DCEN = 1, SER//SEL = 1) Standby/Partial Power-Down Modes of Operation (SER/PAR/SEL = 0 or SER/PAR/SEL = 1) APPLICATION HINTS LAYOUT OUTLINE DIMENSIONS ORDERING GUIDE