Datasheet Linear Technology LTC2485

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Design Notes

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  “Easy Drive” Delta-Sigma Analog-to-Digital Converters Cancel Input Current Errors &mdash DN368
  PDF, 75 Kb, File published: Jun 2, 2005
  Extract from the document

  “Easy Drive” Delta-Sigma Analog-to-Digital Converters
  Cancel Input Current Errors – Design Note 368
  Mike Mayes
  Introduction
  It is now possible to place large RC networks directly in front of high resolution ∆Σ analog-to-digital
  converters without degrading their DC accuracy
  (see Figure 1). The LTC В®248x family of converters
  solves this problem with Easy Driveв„ў technology,
  a fully passive sampling network that automatically
  cancels the differential input current. Easy Drive
  technology does not use on-chip buffers, which
  compromise performance (see What is Wrong with
  On-Chip Buffers?), but instead uses a new architecture
  that maintains 0.002% full-scale error with input RC
  networks up to 100kО© and 10ОјF. This new technology
  offers many advantages over previous generation ∆Σ
  ADCs: Rail-to-rail common mode input range Direct digitization of high impedance sensors Elimination of sampling spikes seen at the ADC input
  pins Simple external lowpass filtering Noise/power reduction Cancellation of external RC settling errors Easy interface to external amplifiers Removal of transmission line effects for remote
  sensors
  RSOURCE
  SENSOR IDIFF = 0
  RSOURCE VIN+
  CEXT Easy Drive …

• Download
  Easy Drive ADCs Simplify Measurement of High Impedance Sensors &mdash DN379
  PDF, 146 Kb, File published: Oct 26, 2005
  Extract from the document

  advertisement Easy Driveв„ў ADCs Simplify Measurement of
  High Impedance Sensors – Design Note 379
  Mark Thoren
  Delta-sigma ADCs, with their high accuracy and high noise
  immunity, are ideal for directly measuring many types
  of sensors. Nevertheless, input sampling currents can
  overwhelm high source impedances or low-bandwidth,
  micropower signal conditioning circuits. The LTCВ®2484
  family of delta sigma converters solves this problem by
  balancing the input currents, thus simplifying or eliminating the need for signal conditioning circuits.
  A common application for a delta-sigma ADC is thermistor
  measurement. Figure 1 shows the LTC2484 connections
  for direct measurement of thermistors up to 100kО©. Data
  I/O is through a standard SPI interface and the sampling
  current in each input is approximately:
  вЋ› VREF вЋћ
  вЋњвЋќ
  ⎟ – VCM
  V + + VIN–
  2 вЋ 
  , where VCM = IN
  1.5MΩ
  2 …

Articles

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  Easy Drive Delta-Sigma ADCs Deliver Powerful Features and Reduce Design Effort &mdash LT Journal
  PDF, 346 Kb, File published: Jan 28, 2008
  Extract from the document

  LINEAR TECHNOLOGY MArch 2007 IN THIS ISSUE…
  Cover Article
  Easy Drive Delta-Sigma ADCs Deliver
  Powerful Features and Reduce Design
  Effort.1
  Mark Thoren Linear Technology in the News….2
  Design Features
  Current Mode Flyback DC/DC Controller
  Provides Tremendous Design Flexibility
  .8
  Arthur Kelley Isolated Forward Controllers Offer
  Buck Simplicity and Performance.10
  Charles Hawkes and Arthur Kelley Rugged 3.3V RS485/RS422
  Transceivers with Integrated
  Switchable Termination.14
  Steven Tanghe and Ray Schuler Tiny High Efficiency 2A Buck Regulator
  Directly Accepts Automotive, Industrial
  and Other Wide Ranging Inputs.18
  Kevin Huang 36V Dual 1.4A Monolithic
  Step-Down Converter has Start-Up
  Tracking and Sequencing.21 VOLUME XVII NUMBER 1 Easy Drive Delta-Sigma
  ADCs Deliver Powerful
  Features and Reduce …

• Download
  Connect High Impedance Sensors Directly to an Easy Drive Delta Sigma ADC &mdash LT Journal
  PDF, 123 Kb, File published: Sep 1, 2005
  Extract from the document

  DESIGN IDEAS Connect High Impedance Sensors
  Directly to an Easy Drive
  Delta Sigma ADC
  by Mark Thoren
  Delta Sigma ADCs are accurate and
  have high noise immunity, making
  them ideal for directly measuring many
  types of sensors. Nevertheless, input
  sampling currents can overwhelm
  high source impedances or low-bandwidth, micropower signal conditioning
  circuits. The LTC2480 family of Delta
  Sigma converters solves this problem
  by balancing the input currents, thus
  simplifying or eliminating the need for
  signal conditioning circuits.
  A common application for a delta
  sigma ADC is thermistor measurement. Figure 1 shows the LTC2480
  connections for direct measurement of
  thermistors up to 100kО©. Data I/O is
  through a standard SPI interface, and
  the sampling current in each input is
  approximately 5V
  C8 …

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Manufacturer's Classification

• Data Conversion > Analog-to-Digital Converters (ADC) > Precision ADCs (Fs < 10Msps) > Single Channel ADCs