Datasheet AD7484 (Analog Devices)

3 MSPS, 14-Bit SAR ADC AD7484 FEATURES FUNCTIONAL BLOCK DIAGRAM Fast throughput rate: 3 MSPS AVDD AGND CBIAS DVDD VDRIVE DGND Wide input bandwidth: 40 MHz No pipeline delays with SAR ADC 2.5V Excellent dc accuracy performance REFOUT REFERENCE BUF 2 parallel interface modes REFSEL REFIN Low power: 90 mW (full power) and 2.5 mW (nap mode) Standby mode: 2 μA maximum 14-BIT ALGORITHMIC Single 5 V supply operation VIN T/H SAR Internal 2.5 V reference Full-scale overrange mode (using 15th bit) AD7484 System offset removal via user access offset register D14 MODE1 Nominal 0 V to 2.5 V input with shifted range capability D13 MODE2 D12 Pin compatible upgrade of 12-bit AD7482 CLIP CONTROL D11 NAP LOGIC AND I/O REGISTERS D10 STBY D9 RESET D8 CONVST D7 E Y
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CS RD S D0 D1 D2 D3 D4 D5 D6 IT
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02 Figure 1.
GENERAL DESCRIPTION
The AD7484 is a 14-bit, high speed, low power, successive alive for a quick power-up while consuming 2.5 mW, and a approximation ADC. The part features a parallel interface with standby mode that reduces power consumption to a mere 10 μW. throughput rates up to 3 MSPS. The part contains a low noise, The AD7484 features an on-board 2.5 V reference but can also wide bandwidth track-and-hold that can handle input frequencies accommodate an externally provided 2.5 V reference source. in excess of 40 MHz. The nominal analog input range is 0 V to 2.5 V, but an offset The conversion process is a proprietary algorithmic successive shift capability allows this nominal range to be offset by ±200 mV. approximation technique that results in no pipeline delays. The This allows the user considerable flexibility in setting the bottom input signal is sampled, and a conversion is initiated on the falling end reference point of the signal range, a useful feature when edge of the CONVST signal. The conversion process is controlled using single-supply op amps. by an internally trimmed oscillator. Interfacing is via standard The AD7484 also provides an 8% overrange capability via a parallel signal lines, making the part directly compatible with 15th bit. Therefore, if the analog input range strays outside the microcontrollers and DSPs. nominal range by up to 8%, the user can still accurately resolve The AD7484 provides excellent ac and dc performance specifica- the signal by using the 15th bit. tions. Factory trimming ensures high dc accuracy, resulting in The AD7484 is powered by a 4.75 V to 5.25 V supply. The part very low INL, offset, and gain errors. also provides a VDRIVE pin that allows the user to set the voltage The part uses advanced design techniques to achieve very low levels for the digital interface lines. The range for this VDRIVE pin power dissipation at high throughput rates. Power consumption is 2.7 V to 5.25 V. The part is housed in a 48-lead LQFP package in the normal mode of operation is 90 mW. There are two power and is specified over a −40°C to +85°C temperature range. saving modes: a nap mode, which keeps the reference circuitry
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Document Outline Features Functional Block Diagram General Description Revision History Specifications Timing Characteristics Absolute Maximum Ratings ESD Caution Pin Configuration and Function Descriptions Typical Performance Characteristics Terminology Circuit Description Converter Operation Analog Input ADC Transfer Function Power Saving Offset/Overrange Parallel Interface Reading Data from the AD7484 Writing to the AD7484 Driving the CONVST Pin Typical Connection Board Layout and Grounding Outline Dimensions Ordering Guide