Fundamentals of sampled data systems



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Fundamentals of sampled data systems

  • Fundamentals of sampled data systems

  • A/D Converters Architectures

    • SAR
    • Sigma-Delta
    • Flash
    • Pipelined
  • D/A Converters Architectures

    • 1 Bit DAC
    • The Kelvin Divider or String DAC
    • Thermometer DAC
    • Binary-Weighted DAC
    • R-2R Ladder DAC
    • Segmented DAC
    • Oversampling Interpolating DAC
    • Multiplying DAC
  • A/D and D/A Converters State of the Art



Sound

  • Sound

  • Light intensity

  • Temperature

  • Force

  • pH...

  • in other words...

  • ...the Real World









































































































Today’s solution

  • Today’s solution





Successive Approximation Converter

  • Successive Approximation Converter

    • Why not? It is the most common and easy to use type of converter, with practically all combinations of speed, resolution, channel count, input interface, output interface, size and cost.
      • AD7626 is the fastest 16 bit SAR at 10MSPS
      • AD7690 is the highest SNR 101.5dB
      • AD7468 is the lowest power (570uW at 200kSPS, lower if run slower)
      • AD7276 is a good all-rounder, 12 bits, 3MSPS, TSOT-6, 3.6mW
    • Unbeatable for high resolution measurements with low-delay
    • Unbeatable for multiplexed applications
    • Can be optimised for low-power (sleep mode between conversions)
    • Can be optimised for low noise (averaging or filtering the output)


Precision Sigma Delta converter

  • Precision Sigma Delta converter

    • Low noise and accuracy for DC measurements
      • Best is AD7190, AD7191, AD7195
    • Integrated Sensor conditioning and System-on-chip
      • AD779x family have buffers, muxes, current sources, reference inputs to suit various temperature, pressure and other sensors.
    • Low power at low data rates
      • AD7171 needs only 330uW for full operation (but SAR can be even lower power if put to sleep between conversions at very low sample rates)
    • Robustness
      • AD7190 has 50/60Hz rejection of 120dB


Fast Sigma Delta converter

  • Fast Sigma Delta converter

    • Accurate DC and AC measurements, stable over temperature
      • e.g. AD7764 has offset & gain drift <1ppm/°C
    • Flat frequency response over the pass band
      • AD7764 filter has 0.1dB ripple
    • Wide Dynamic range over a wide bandwidth
      • AD7764 has 115dB Dynamic range
    • Robustness
      • AD7764 has excellent anti-aliasing performance


Pipelined Converter

  • Pipelined Converter

    • When you need to retain good AC performance over wide bandwidths or at high signal freqencies
      • AD9434 is a 12 bit 500 MSPS converter. ENOB = 10.4 at 450MHZ
      • AD9467 is a 16 bit 250 MSPS converter. SFDR = 100dB at 170MHz allowing very small signals to be detected in the presence of very large ones
    • When you need to measure a signal with very high sample rate
      • AD9286 toggles 2 ADCs to achieve 500MSPS. It is targeted at Oscilloscope applications and other time-domain measurements




  • Input is purely passive

    • 1kohm differential input resistor for 85dB SNR (10MHz BW, 2Vpp)
    • Driver amplifier may be removed
    • Input impedance is real vs. complex
  • Low NF allows reduced gain before ADC => more linear front-end

    • Typical Pipeline ADC: NF=22
      • -78dBFS at 125MHz, +4dBm fullscale, 0.4W/ADC = -152dBm/Hz
    • AD9262: NF=15
      • -86dBFS over 10MHz, -3dBm fullscale, 0.35W/ADC = -158dBm/Hz






























Technology Leadership:

  • Technology Leadership:

  • Meeting customer need for faster sampling rate

  • No compromise on performance, keeping power to a minimum



Features

  • Features

  • Fast Throughput, High Performance

    • 10 MSPS (AD7626)
    • 6 MSPS (AD7625)
  • SAR architecture

  • 16-bit resolution with no missing codes

  • SNR: 92 dB Typ, 90dB Min @ 1MHz

  • INL: ±1 LSB Typ, ±2 LSB Max

  • DNL: ±0.3 LSB Typ, ±1 LSB Max

  • Differential input range: ± 4.096V

  • No latency/no pipeline delay

  • Serial LVDS interface

  • On-Board 4.096V Reference

  • Power dissipation 130 mW @ 10 MSPS, 100 mW @ 6 MSPS



The World Lowest Power 16-Bit ADC

  • The World Lowest Power 16-Bit ADC

    • Lowest Power: 7mW @ 1MSPS
    • Power scales linearly with sampling rate like 70W @ 10kSPS
  • The World Smallest Package in > 0.2MSPS 16-Bit ADC

    • LFSCP/QFN (SOT23 size) or MSOP
    • Pin-Pin compatible with AD768x
  • The World fastest MSOP/QFN 16-Bit ADC

  • Outstanding DC and AC Performance

    • 16-Bit No Missing Code
    • +/-1.5LSB INL Max
    • 20bit effective resolution @ 10kSPS
  • Ease of use

    • 2.5V main supply
    • 0 to REF input (up to 5V) - lower cost opamp -
    • 5V/3.3V/2.5V serial SPI
    • Multiple ADC Daisy Chain, Busy Indicator




High Performance

  • High Performance

    • Maintains leadership position: Smallest, Fastest, Lowest Power
  • Features

    • Lowest power:
      • 15mW@ 2MSPS w/o reference
      • 26mW@ 2MSPS w/reference
    • Throughput:
      • 2MSPS Turbo= HIGH
      • 1.5MSPS Turbo= LOW
    • 1.8V/2.5V/2.7V serial SPI
    • SNR 97dB w/external VREF
    • Pin for pin with AD7985 (16b), AD7944 (14b)








Low Power – 400 μA typical

  • Low Power – 400 μA typical

  • Low Noise – 40 nV rms

  • Programmable Integrated Features for Temperature Sensing

      • (RTDs, Thermocouples, Thermistors)
    • Instrumentation Amplifier (binary gains 1 to 128)
    • Excitation Current Sources (10 / 210 / 1000 µA)
    • Voltage Reference, Clock
    • Input Buffer, Temp Sensor
  • Superior offset & gain drift specs

    • Offset = 10 nV/°C; Gain = 1 ppm/°C
  • Simultaneous 50 & 60 Hz Rejection

  • 4 Hz to 470 Hz Output Data Rate

  • Supply: 2.7 V to 5.25 V

  • Temp: -40°C to +105°C

    • +125°C option for AD7794


KEY APPLICATION BENEFITS

  • KEY APPLICATION BENEFITS

  • 3-wire RTD

      • 2 matched excitation currents
      • 40 nV RMS @ Gain = 64
      • Ratiometric Configuration
      • 50 & 60 Hz Rejection (-70 dB)


KEY APPLICATION BENEFITS

  • KEY APPLICATION BENEFITS

  • Thermocouple

    • Internal Reference
    • 40 nV RMS @ Gain = 64, 4 Hz Update Rate
    • Differential Analog Input
    • On-chip VBIAS Centers the Sensor Range
    • 50 & 60 Hz Rejection


KEY APPLICATION BENEFITS

  • KEY APPLICATION BENEFITS

  • Flow Sensor

      • Several channels required
      • 40 nV RMS Noise (In-Amp Gain = 64)
      • REFIN up to AVDD
      • Ratiometric Configuration
      • 50 & 60 Hz Rejection (-70 dB)


KEY APPLICATION BENEFITS

  • KEY APPLICATION BENEFITS

    • 27 nV noise (In-Amp Gain = 128, 4 Hz Update Rate)
    • REFIN up to AVDD
    • Ratiometric Configuration
    • Medium/High Range Weigh Scales (1 count in 112, 000 (±10 mV Input Range))
    • 50 & 60Hz Rejection (-70 dB)




Scientific, Test & Commercial Instruments

  • Scientific, Test & Commercial Instruments

    • Weigh Scales (Retail, Laboratory, Industrial Hopper & Conveyer Scales)
    • Chromatography for Chemical Analysis
    • Data Acquisition / Analyzers
    • Dataloggers
  • Industrial Automation

    • PLC/DCS Analog Input Module Front-Ends
    • Temperature Controllers
    • Pressure Measurement
  • Medical Instrumentation

    • Patient Monitoring
      • Blood Pressure Measurement, Temperature Measurement, Blood Analysis




KEY BENEFITS

  • KEY BENEFITS

  • High SNR allows accurate digitization

      • 112dB at 78kHz, 100dB at 2.5 MHz
      • Reduced anti aliasing filtering (Sigma/Delta)
  • Flexibility

      • Filter Programmability allows application customization
  • Comprehensive Solution

      • On Chip Buffer/Amplifiers simplify design - no need for user to select expensive external components






KEY SPECIFICATIONS

  • KEY SPECIFICATIONS

  • A/C Performance at 500Msps

    • SNR = 65.2 dBFS @ Ain up to 250 MHz
    • ENOB of 10.5 @ fIN up to 250 MHz
    • SFDR = 75 dBc @ fIN up to 250 MHz
  • LVDS SDR at 500 MSPS (ANSI-644 levels)

  • 1.2 GHz full power analog bandwidth

  • On-chip reference, no external decoupling required

    • Programmable via SPI
  • Integrated input buffer and S/H

  • Programmable input voltage range:

    • 1.18 V to 1.6 V, 1.5 V nominal
  • Low power dissipation

    • 660 mW @ 500 MSP—LVDS SDR mode
  • Single 1.8 V supply operation

  • SPI Port for configuration and control

    • Selectable output data format (offset binary, twos complement, Gray code)
    • Power down
    • Output Test patterns
    • Output timing adjustments


KEY SPECIFICATIONS

  • KEY SPECIFICATIONS

  • A/C Performance at 500Msps

    • SNR = 47 dBFS @ Ain up to 250 MHz
    • ENOB of 7.5 @ fIN up to 250 MHz
    • SFDR = 83 dBc @ fIN up to 250 MHz
  • LVDS SDR at 500 MSPS (ANSI-644 levels)

  • 1.2 GHz full power analog bandwidth

  • On-chip reference, no external decoupling required

    • Programmable via SPI
  • Integrated input buffer and S/H

  • Programmable input voltage range:

    • 1.18 V to 1.6 V, 1.5 V nominal
  • Low power dissipation

    • 670 mW @ 500 MSP—LVDS SDR mode
  • Single 1.8 V supply operation

  • SPI Port for configuration and control

    • Selectable output data format (offset binary, twos complement, Gray code)
    • Power down
    • Output Test patterns
    • Output timing adjustments








1ppm Linearity

  • 1ppm Linearity

    • 20bit Resolution
    • 1ppm DNL & INL
  • <1ppm Noise

    • 0.025ppm Low freq Noise
    • 9nV√Hz Wide Band Noise
  • 1µs Settling Time

    • ¼ to ¾ scale settling
  • <1ppm Drift

    • Offset Drift 0.05ppm/°C
  • Low Glitch

    • 0.4nV·s (5v); 1nV·s (10v)
  • Output Spans +5V to ±10V

  • ± 7.5 V to ±15 V Power Supply





MRI DAC Requirements:

  • MRI DAC Requirements:

  • High Resolution/Accuracy

    • 18-20 bits minimum for ≥3.0Tesla Systems
  • Low Noise

    • Lessens unwanted image artifacts thereby reducing the need for multiple MRI scans
  • Low Drift

    • Eliminates system calibrations
  • Fast Settling Time

    • Reduces scan time


Single Channel Configuration for Isolated PLC Systems

  • Single Channel Configuration for Isolated PLC Systems

    • 16-Bit Resolution
  • IOUT

    • 4mA-20mA, 0mA-20mA or 0mA-24mA
    • ±0.01% FSR TUE
    • 4ppm/oC Output Drift
  • VOUT

    • 0-5V, 0-10V, ±5V, ±10V
    • 10% over-range
    • 0.01% FSR TUE
    • 3ppm/oC Output Drift
    • Force & Sense capability
  • Functionality

    • Internal 5V 10ppm/oC Reference
    • Diagnostics/Fault detection
    • Output Loop compliant AVDD-2.5V




16-Bit Quad Industrial V/I Output DAC with Thermal Control

  • 16-Bit Quad Industrial V/I Output DAC with Thermal Control

  • IOUT Range:

    • 4-20mA, 0-20mA or 0-24mA
    • 0.06% TUE Accuracy
    • 5ppm/oC Output Drift
  • VOUT Range:

    • 0-5V, 0-10V, ±5V, ±10V
    • 20% Over-range.
    • 0.04% TUE
    • Vsense + & Vsens -
  • Functionality

    • Flexible Digital Interface
    • On-chip Diagnostics
    • Integrated per channel DC-DC for Dynamic Power Control
    • Internal 5ppm/oC Reference
    • Housed in 64 – LFCSP (9 x 9mm)


Smart and High- Efficiency Dynamic Power Control (DPC)

  • Smart and High- Efficiency Dynamic Power Control (DPC)



KEY BENEFITS

  • KEY BENEFITS

  • Small: 32 lead TQFP

  • Full 16 Bit Accuracy

    • 1 LSB DNL
    • 1 LSB INL(C-Grade)
    • 2/4 LSB INL (B/A-Grade)
  • Ease of Application

    • On chip reference buffers
    • Bipolar output generated from single 5V Ref
  • Output control during power on/off

    • Output clamped to 0V during power on/off




















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