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Notas de Diseño

• Descargar
  DC Accurate Driver for the LTC2377-20 Achieves 2ppm Linearity &mdash DN1032
  PDF, 189 Kb, Archivo publicado: enero 6, 2014
  Extracto del documento

  DC Accurate Driver for the LTC2377-20 Achieves
  2ppm Linearity – Design Note 1032
  Guy Hoover
  Introduction
  As resolution and sample rates continue to rise for
  analog-to-digital converters (ADCs), the driver circuitry
  for the ADC analog input, not the ADC itself, has increasingly become the limiting factor in determining
  overall circuit accuracy. First, the driver circuitry must
  buffer the input signal and provide gain. In addition,
  it must level shift or convert a single-ended signal to
  a fully differential signal to satisfy the input voltage
  range and common mode requirements of the ADC.
  All must be done without adding distortion to the
  original signal. by the LTC2377-20 (U1). The LTC2377-20 is a 20-bit,
  500ksps, low power SAR ADC with a typical integral
  nonlinearity (INL) of В±0.5ppm. The voltage at AIN is
  buffered by U4, which in turn drives the U5 resistor
  string, acting as a precision divider. U3 operates in
  a gain of minus one-half and drives the center of the
  U5 resistor string to maintain the ADC common mode
  voltage at VREF/2.
  U3 and U4 are LTВ®1468A low offset highly linear
  op amps. U5 is a LT5400A quad matched resistor …

• Descargar
  Low Noise, Precision Op Amp Drives High Resolution SAR ADCs &mdash DN1039
  PDF, 263 Kb, Archivo publicado: agosto 23, 2016
  Extracto del documento

  Low Noise, Precision Op Amp Drives High Resolution
  SARВ ADCs
  Design Note 1039
  Erjon Qirko and Kris Lokere
  Introduction
  The LT6018 is an ultralow noise (1.2nV/в€љHz at 1kHz)
  operational amplifier with ultralow distortion (–115dB
  at 1kHz). It has a gain bandwidth product of 15MHz,
  maximum offset voltage of 50ВµV and a maximum
  offset voltage drift of 0.5ВµV/В°C. This combination
  of features makes it suitable for driving a variety of
  high resolution analog-to-digital converters (ADCs).
  This Design Note presents circuits and optimization
  strategies to achieve the best signal-to-noise ratio
  (SNR) and total harmonic distortion (THD) when
  using the LT6018 to drive high speed 18-bit and 20bit successive approximation register (SAR) ADCs. LTC2378-20 stands out for its unrivaledВ 2ppm linearity
  performance. The best way to create a differential
  signal while maintaining linearity is by using the
  precision matched resistors in the LT5400 used on
  this demo board. A detailed theory of operation for
  the circuit shown in Figure 1 appears in Design Note
  1032 (where the LT1468 drives the LTC2377-20).
  To measure the circuit’s linearity, an ultrapure sine …

Artículos

• Descargar
  DC Accurate Driver for 20-Bit SAR ADC Achieves 2ppm Linearity &mdash LT Journal
  PDF, 170 Kb, Archivo publicado: jul 1, 2014
  Extracto del documento

  DC Accurate Driver for 20-Bit SAR ADC Achieves 2ppm
  Linearity
  Guy Hoover As resolution and sample rates continue to rise for analogto-digital converters (ADCs), the driver circuitry for the ADC
  analog input, not the ADC itself, has increasingly become the
  limiting factor in determining overall circuit accuracy. First,
  the driver circuitry must buffer the input signal and provide
  gain. In addition, it must level shift or convert a single-ended
  signal to a fully differential signal to satisfy the input voltage
  range and common mode requirements of the ADC. All must
  be done without adding distortion to the original signal. turn drives the U5 resistor string, acting as
  a precision divider. U3 operates in a gain
  of minus one-half and drives the center
  of the U5 resistor string to maintain the
  ADC common mode voltage at VREF/2.
  U3 and U4 are LT1468A low offset highly
  linear op amps. U5 is a LT5400A quad
  matched resistor network with a guaranteed maximum mismatch of 0.01%.
  Matched resistor values in U5 are important because any mismatch contributes
  to both offset and full-scale error in
  this circuit. For this reason and because
  of their extremely low voltage coefficient, do not use discrete resistors
  instead of the LT5400A. R4 provides a
  quarter-scale shift to the output of U3. …

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Clasificación del fabricante

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