2 LC MOS 8-Channel, 12-Bit Serial Data Acquisition System AD7890 FEATURES FUNCTIONAL BLOCK DIAGRAM V Fast 12-bit ADC with 5.9 s conversion time MUX SHA REF OUT/ DD OUT IN REF IN Eight single-ended analog input channels Selection of input ranges: SIGNAL V IN1 2k 1 2.5V SCALING REFERENCE 10 V for AD7890-10 V SIGNAL IN2 1 0 V to 4.096 V for AD7890-4 SCALING 0 V to 2.5 V for AD7890-2 V SIGNAL IN3 1 SCALING C EXT Allows separate access to multiplexer and ADC V SIGNAL IN4 1 SCALING On-chip track/hold amplifier MUX V SIGNAL On-chip reference IN5 1 SCALING CONVST High-speed, flexible, serial interface V SIGNAL IN6 12-BIT 1 SCALING Single supply, low-power operation (50 mW maximum) ADC V SIGNAL IN7 Power-down mode (75 W typ) 1 SCALING TRACK/HOLD V SIGNAL IN8 GENERAL DESCRIPTION 1 SCALING OUTPUT/CONTROL REGISTER AD7890 The AD7890 is an 8-channel 12-bit data acquisition system. The CLOCK part contains an input multiplexer, an on-chip track/hold amplifier, a high speed 12-bit ADC, a 2.5 V reference, and a AGND AGND DGND CLK SCLK TFS RFS DATA DATA SMODE IN OUT IN high speed, serial interface. The part operates from a single 5 V 1 NO SCALING ON AD7890-2 supply and accepts an analog input range of 10 V (AD7890-10), Figure 1. 0 V to 4.096 V (AD7890-4), and 0 V to 2.5 V (AD7890-2). Power dissipation in normal mode is low at 30 mW typical and the The multiplexer on the part is independently accessible. This part can be placed in a standby (power-down) mode if it is not allows the user to insert an antialiasing filter or signal required to perform conversions. The AD7890 is fabricated in conditioning, if required, between the multiplexer and the 2 Analog Devices, Inc.s Linear Compatible CMOS (LC MOS) ADC. This means that one antialiasing filter can be used for all process, a mixed technology process that combines precision eight channels. Connection of an external capacitor allows the bipolar circuits with low power CMOS logic. The part is available user to adjust the time given to the multiplexer settling to in a 24-lead, 0.3 wide, plastic or ceramic dual-in-line package or in include any external delays in the filter or signal conditioning a 24-lead small outline package (SOIC W). circuitry. PRODUCT HIGHLIGHTS Output data from the AD7890 is provided via a high speed bidirectional serial interface port. The part contains an on-chip 1. Complete 12-Bit Data Acquisition System-on-a-Chip. control register, allowing control of channel selection, The AD7890 is a complete monolithic ADC combining an conversion start, and power-down via the serial port. Versatile, 8-channel multiplexer, 12-bit ADC, 2.5 V reference, and a high speed logic ensures easy interfacing to serial ports on track/hold amplifier on a single chip. microcontrollers and digital signal processors. 2. Separate Access to Multiplexer and ADC. The AD7890 provides access to the output of the In addition to the traditional dc accuracy specifications such as multiplexer allowing one antialiasing filter for 8 channels linearity, full-scale, and offset errors, the AD7890 is also a considerable savings over the 8 antialiasing filters required if specified for dynamic performance parameters including the multiplexer is internally connected to the ADC. harmonic distortion and signal-to-noise ratio. 3. High Speed Serial Interface. The part provides a high speed serial interface for easy connection to serial ports of microcontrollers and DSP processors. Rev. C Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. 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Trademarks and registered trademarks are the property of their respective owners. 01357-001AD7890 TABLE OF CONTENTS Features .............................................................................................. 1 Serial Interface ................................................................................ 17 General Description ......................................................................... 1 Self-Clocking Mode ................................................................... 17 Functional Block Diagram .............................................................. 1 External Clocking Mode ........................................................... 18 Product Highlights ........................................................................... 1 Simplifying the Interface ........................................................... 19 Revision History ............................................................................... 2 Microprocessor/Microcontroller Interface ................................. 20 Specifications..................................................................................... 3 AD7890 to 8051 Interface ......................................................... 20 Timing Specifications .................................................................. 5 AD7890 to 68HC11 Interface ................................................... 20 Absolute Maximum Ratings............................................................ 6 AD7890 to ADSP-2101 Interface ............................................. 21 ESD Caution.................................................................................. 6 AD7890 to DSP56000 Interface ............................................... 21 Pin Configuration and Function Descriptions............................. 7 AD7890 to TMS320C25/30 Interface...................................... 21 Terminology ...................................................................................... 9 Antialiasing Filter....................................................................... 22 Control Register.............................................................................. 10 Performance .................................................................................... 23 Theory of Operation ...................................................................... 11 Linearity....................................................................................... 23 Converter Details........................................................................ 11 Noise ............................................................................................ 23 Circuit Description..................................................................... 11 Dynamic Performance............................................................... 24 Track/Hold Amplifier ................................................................ 12 Effective Number of Bits ........................................................... 24 Reference ..................................................................................... 13 Outline Dimensions....................................................................... 25 Timing and Control ................................................................... 13 Ordering Guide .......................................................................... 27 CEXT Functioning......................................................................... 16 REVISION HISTORY 9/06Rev. B to Rev. C Updated Format..................................................................Universal Changes to Table 1............................................................................ 3 Updated Outline Dimensions ....................................................... 25 Changes to Ordering Guide .......................................................... 27 2/01Rev. A to Rev. B Rev. C Page 2 of 28