Datasheet AD7891 (Analog Devices)

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LC2MOS 8-Channel, 12-Bit High Speed Data Acquisition System AD7891 FEATURES FUNCTIONAL BLOCK DIAGRAM Fast 12-Bit ADC with 1.6
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s Conversion Time REF OUT/ V 8 Single-Ended Analog Input Channels DD VDD REF IN REF GND Overvoltage Protection on Each Channel VIN1A Selection of Input Ranges: 2.5V VIN1B REFERENCE
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5 V,
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10 V for AD7891-1 V STANDBY IN2A V 0 to +2.5 V, 0 to +5 V, AD7891
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2.5 V for AD7891-2 IN2B VIN3A Parallel and Serial Interface VIN3B On-Chip Track/Hold Amplifier VIN4A 12-BIT M On-Chip Reference V ADC IN4B U VIN5A X Single-Supply, Low Power Operation (100 mW Max) VIN5B Power-Down Mode (75
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W Typ) TRACK/HOLD VIN6A VIN6B APPLICATIONS DATA/ VIN7A ADDRESS CONTROL Data Acquisition Systems V DECODE IN7B LINES VIN8A Motor Control VIN8B Mobile Communication Base Stations CLOCK CONTROL LOGIC Instrumentation WR CS RD EOC CONVST MODE AGND AGND DGND GENERAL DESCRIPTION PRODUCT HIGHLIGHTS
The AD7891 is an 8-channel, 12-bit data acquisition system 1. The AD7891 is a complete monolithic 12-bit data acquisition with a choice of either parallel or serial interface structure. The system that combines an 8-channel multiplexer, 12-bit ADC, part contains an input multiplexer, an on-chip track/hold ampli- 2.5 V reference, and track/hold amplifier on a single chip. fier, a high speed 12-bit ADC, a 2.5 V reference, and a high 2. The AD7891-2 features a conversion time of 1.6 ms and an speed interface. The part operates from a single 5 V supply and acquisition time of 0.4 ms. This allows a sample rate of accepts a variety of analog input ranges across two models, the 500 kSPS when sampling one channel and 62.5 kSPS when AD7891-1 (±5 V and ±10 V) and the AD7891-2 (0 V to +2.5 V, channel hopping. These sample rates can be achieved using 0 V to +5 V, and ± 2.5 V). either a software or hardware convert start. The AD7891-1 The AD7891 provides the option of either a parallel or serial has an acquisition time of 0.6 ms when using a hardware interface structure determined by the MODE pin. The part convert start and an acquisition time of 0.7 ms when using a has standard control inputs and fast data access times for both software convert start. These acquisition times allow sample the serial and parallel interfaces, ensuring easy interfacing to rates of 454.5 kSPS and 435 kSPS, respectively, for hardware modern microprocessors, microcontrollers, and digital signal and software convert start. processors. 3. Each channel on the AD7891 has overvoltage protection. This In addition to the traditional dc accuracy specifications, such as means an overvoltage on an unselected channel does not affect linearity, full-scale and offset errors, the part is also specified for the conversion on a selected channel. The AD7891-1 can dynamic performance parameters, including harmonic distortion withstand overvoltages of ±17 V. and signal-to-noise ratio. Power dissipation in normal mode is 82 mW typical; in the standby mode, this is reduced to 75 mW typ. The part is available in a 44-terminal MQFP and a 44-lead PLCC. REV. D 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 rights of third parties that may result from its use. No license is granted by implication or otherwise
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Document Outline FEATURES APPLICATIONS GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAM PRODUCT HIGHLIGHTS SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS TIMING CHARACTERISTICS ORDERING GUIDE PIN CONFIGURATIONS PIN FUNCTION DESCRIPTIONS PARALLEL INTERFACE MODE FUNCTIONS Data I/O Lines Parallel Read Operation SERIAL INTERFACE MODE FUNCTIONS CONTROL REGISTER TERMINOLOGY Signal-to-(Noise + Distortion) Ratio Total Harmonic Distortion (THD) Peak Harmonic or Spurious Noise Intermodulation Distortion Channel-to-Channel Isolation Relative Accuracy Differential Nonlinearity Positive Full-Scale Error (AD7891-1, ±10 V and ±5 V; AD7891-2, ±2.5 V) Positive Full-Scale Error (AD7891-2, 0 V to 5 V and 0 V to 2.5 V) Bipolar Zero Error (AD7891-1, ±10 V and ±5 V; AD7891-2, ±2.5 V) Unipolar Offset Error (AD7891-2, 0 V to 5 V and 0 V to 2.5 V) Negative Full-Scale Error (AD7891-1, ±10 V and ±5V; AD7891-2, ±2.5 V) Track/Hold Acquisition Time CONVERTER DETAILS INTERFACE INFORMATION Parallel Interface Mode Serial Interface Mode Simplifying the Serial Interface CIRCUIT DESCRIPTION Reference Analog Input Section Track/Hold Amplifier STANDBY Operation MICROPROCESSOR INTERFACING AD7891 to 8X51 Serial Interface AD7891 to 68HC11 Serial Interface AD7891 to ADSP-21xx Serial Interface AD7891 to DSP5600x Serial Interface AD7891 to TMS320xxx Serial Interface PARALLEL INTERFACING AD7891 to ADSP-21xx AD7891 to TMS32020, TMS320C25, and TMS320C5x AD7891 to TMS320C3x AD7891 to DSP5600x Power Supply Bypassing and Grounding AD7891 PERFORMANCE Linearity Noise Dynamic Performance Effective Number of Bits OUTLINE DIMENSIONS Revision History