SBOA585 March   2024 ADS127L11 , ADS127L11 , ADS127L21 , ADS127L21 , PGA849 , PGA849 , PGA855 , PGA855

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1PGA855 and ADS127L21, 24-Bit, Delta-Sigma ADC Driver Circuit
  5. 2PGA855 Analog Front-End Filters
  6. 3ADS127Lx1 Delta-Sigma ADC and Digital Filter
  7. 4Approximate PGA855 Intrinsic Noise Analysis
    1. 4.1 Simplified Noise Model for the PGA855
    2. 4.2 PGA855 Spectral Noise Density vs Frequency
    3. 4.3 PGA855 Effective Noise Bandwidth
    4. 4.4 PGA855 Low Frequency (1/f) Noise Calculation
    5. 4.5 PGA855 Voltage Broadband Noise
    6. 4.6 PGA855 Current Noise and Source Resistance
    7. 4.7 PGA855 Total Noise
  8. 5PGA855 and ADS127Lx1 System Noise
  9. 6PGA855 and ADS127Lx1 SNR and Noise Calculator
  10. 7PGA855 and ADS127Lx1 FFT Measured Performance
  11. 8Summary
  12. 9References

Abstract

The PGA855 is a precision, wide-bandwidth programmable gain instrumentation amplifier with fully differential outputs optimized to drive high-performance analog-to-digital converters (ADCs) with fully differential inputs. The PGA855 is equipped with eight binary gain settings, from an attenuating gain of 0.125V/V to a maximum of 16V/V, using three digital gain-selection pins. The low-noise current-feedback front-end architecture offers excellent gain flatness, even at high frequencies, making the PGA855 an excellent high-impedance sensor readout device. Integrated protection circuitry on the input pins handles overvoltages up to ±40V beyond the power supply voltages. The PGA855 offers an excellent combination of AC performance and DC accuracy, making the PGA855 a versatile choice for a variety of sensors.

This application note shows the AC performance of the PGA855 driving the ADS127L11 and ADS127L21 delta-sigma ADCs. The focus of this document is on intrinsic noise, signal-to-noise ratio (SNR) and effective resolution performance. In particular, this application note provides guidelines of the analog filter selection and provides the performance of the PGA855 and ADS127Lx1 with different data rates and digital filter settings.

The document illustrates a step-by-step intrinsic noise analysis of the acquisition system, provides a calculator tool to estimate the system performance with different ADC digital filter and data rate settings, and shows the bench measurements of the PGA855 driving the ADS127Lx1.