SBASB74 October   2024 ADS127L21B

PRODUCTION DATA  

  1.   1
  2. Features
  3. Applications
  4. Description
  5. Pin Configuration and Functions
  6. Specifications
    1. 5.1  Absolute Maximum Ratings
    2. 5.2  ESD Ratings
    3. 5.3  Recommended Operating Conditions
    4. 5.4  Thermal Information
    5. 5.5  Electrical Characteristics
    6. 5.6  Timing Requirements (1.65V ≤ IOVDD ≤ 2V)
    7. 5.7  Switching Characteristics (1.65V ≤ IOVDD ≤ 2V)
    8. 5.8  Timing Requirements (2V < IOVDD ≤ 5.5V)
    9. 5.9  Switching Characteristics (2V < IOVDD ≤ 5.5V)
    10. 5.10 Timing Diagrams
    11. 5.11 Typical Characteristics
  7. Parameter Measurement Information
    1. 6.1  Offset Error Measurement
    2. 6.2  Offset Drift Measurement
    3. 6.3  Gain Error Measurement
    4. 6.4  Gain Drift Measurement
    5. 6.5  NMRR Measurement
    6. 6.6  CMRR Measurement
    7. 6.7  PSRR Measurement
    8. 6.8  SNR Measurement
    9. 6.9  INL Error Measurement
    10. 6.10 THD Measurement
    11. 6.11 IMD Measurement
    12. 6.12 SFDR Measurement
    13. 6.13 Noise Performance
  8. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Analog Input (AINP, AINN)
        1. 7.3.1.1 Input Range
      2. 7.3.2 Reference Voltage (REFP, REFN)
        1. 7.3.2.1 Reference Voltage Range
      3. 7.3.3 Clock Operation
        1. 7.3.3.1 Internal Oscillator
        2. 7.3.3.2 External Clock
      4. 7.3.4 Modulator
      5. 7.3.5 Digital Filter
        1. 7.3.5.1 Wideband Filter
          1. 7.3.5.1.1 Wideband Filter Options
          2. 7.3.5.1.2 Sinc5 Filter Stage
          3. 7.3.5.1.3 FIR1 Filter Stage
          4. 7.3.5.1.4 FIR2 Filter Stage
          5. 7.3.5.1.5 FIR3 Filter Stage
          6. 7.3.5.1.6 FIR3 Default Coefficients
          7. 7.3.5.1.7 IIR Filter Stage
            1. 7.3.5.1.7.1 IIR Filter Stability
        2. 7.3.5.2 Low-Latency Filter (Sinc)
          1. 7.3.5.2.1 Sinc3 and Sinc4 Filters
          2. 7.3.5.2.2 Sinc3 + Sinc1 and Sinc4 + Sinc1 Cascade Filter
      6. 7.3.6 Power Supplies
        1. 7.3.6.1 AVDD1 and AVSS
        2. 7.3.6.2 AVDD2
        3. 7.3.6.3 IOVDD
        4. 7.3.6.4 Power-On Reset (POR)
        5. 7.3.6.5 CAPA and CAPD
      7. 7.3.7 VCM Output Voltage
    4. 7.4 Device Functional Modes
      1. 7.4.1 Speed Modes
      2. 7.4.2 Idle Mode
      3. 7.4.3 Standby Mode
      4. 7.4.4 Power-Down Mode
      5. 7.4.5 Reset
        1. 7.4.5.1 RESET Pin
        2. 7.4.5.2 Reset by SPI Register Write
        3. 7.4.5.3 Reset by SPI Input Pattern
      6. 7.4.6 Synchronization
        1. 7.4.6.1 Synchronized Control Mode
        2. 7.4.6.2 Start/Stop Control Mode
        3. 7.4.6.3 One-Shot Control Mode
      7. 7.4.7 Conversion-Start Delay Time
      8. 7.4.8 Calibration
        1. 7.4.8.1 OFFSET2, OFFSET1, OFFSET0 Calibration Registers (Addresses 0Ch, 0Dh, 0Eh)
        2. 7.4.8.2 GAIN2, GAIN1, GAIN0 Calibration Registers (Addresses 0Fh, 10h, 11h)
        3. 7.4.8.3 Calibration Procedure
    5. 7.5 Programming
      1. 7.5.1 Serial Interface (SPI)
        1. 7.5.1.1  Chip Select (CS)
        2. 7.5.1.2  Serial Clock (SCLK)
        3. 7.5.1.3  Serial Data Input (SDI)
        4. 7.5.1.4  Serial Data Output/Data Ready (SDO/DRDY)
        5. 7.5.1.5  SPI Frame
        6. 7.5.1.6  Full-Duplex Operation
        7. 7.5.1.7  Device Commands
          1. 7.5.1.7.1 No-Operation
          2. 7.5.1.7.2 Read Register Command
          3. 7.5.1.7.3 Write Register Command
        8. 7.5.1.8  Read Conversion Data
          1. 7.5.1.8.1 Conversion Data
          2. 7.5.1.8.2 Data Ready
            1. 7.5.1.8.2.1 DRDY
            2. 7.5.1.8.2.2 SDO/DRDY
            3. 7.5.1.8.2.3 DRDY Bit
            4. 7.5.1.8.2.4 Clock Counting
          3. 7.5.1.8.3 STATUS Byte
        9. 7.5.1.9  Daisy-Chain Operation
        10. 7.5.1.10 3-Wire SPI Mode
          1. 7.5.1.10.1 3-Wire SPI Mode Frame Reset
        11. 7.5.1.11 SPI CRC
      2. 7.5.2 Register Memory CRC
        1. 7.5.2.1 Main Program Memory CRC
        2. 7.5.2.2 FIR Filter Coefficient CRC
        3. 7.5.2.3 IIR Filter Coefficient CRC
  9. Register Map
  10. Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 SPI Operation
      2. 9.1.2 Input Driver
      3. 9.1.3 Antialias Filter
      4. 9.1.4 Reference Voltage
      5. 9.1.5 Simultaneous-Sampling Systems
    2. 9.2 Typical Applications
      1. 9.2.1 A-Weighting Filter Design
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
        3. 9.2.1.3 Application Curve
      2. 9.2.2 PGA855 Programmable Gain Amplifier
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
        3. 9.2.2.3 Application Curves
      3. 9.2.3 THS4551 Antialias Filter Design
        1. 9.2.3.1 Design Requirements
        2. 9.2.3.2 Detailed Design Procedure
        3. 9.2.3.3 Application Curves
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Example
  11. 10Device and Documentation Support
    1. 10.1 Documentation Support
      1. 10.1.1 Related Documentation
    2. 10.2 Receiving Notification of Documentation Updates
    3. 10.3 Support Resources
    4. 10.4 Trademarks
    5. 10.5 Electrostatic Discharge Caution
    6. 10.6 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

Noise Performance

The ADC provides four operational speed modes that provide trade-offs between ADC resolution, power consumption, and signal bandwidth. The modes are max speed, high speed, mid speed, and low speed, with decreasing orders of device power consumption. The wideband filter offers data rates up to 512kSPS (max-speed mode), 400kSPS (high-speed mode), 200kSPS (mid-speed mode), and 50kSPS (low-speed mode). Data are also accessible from the partial filters of the intermediate FIR1 or FIR2 stages for reduced filter time latency.

The low-latency sinc4 filter offers data rates up to 1.365MSPS (max-speed mode), 1.066MSPS (high-speed mode), 533kSPS (mid-speed mode), and 133kSPS (low-speed mode).

The programmable oversampling ratio (OSR) determines the output data rate and signal bandwidth, therefore affecting total noise performance. Increasing the OSR lowers the signal bandwidth and total noise by averaging more samples from the modulator to yield one conversion result.

Table 7-12 through Table 6-5 summarize the noise performance of the filters. Noise performance is specified for the 1x input range and a 4.096V reference voltage. In comparison, decreasing the reference voltage to 2.5V decreases dynamic range by 4dB (typical). 2.5V reference voltage and 2x input range operation decreases dynamic range by 3dB (typical) compared to a 4.096V reference voltage and 1x input range operation.

Noise data are the result of the standard deviation (rms) of the conversion data with inputs shorted and biased to the mid-supply voltage. Noise data are representative of typical performance at TA = 25°C. A minimum of 1,000 or 10 seconds of consecutive conversions (whichever occurs first) are used to measure RMS noise (en). Because of the statistical nature of noise, repeated noise measurements potentially yield higher or lower noise results.

Equation 13 converts RMS noise to dynamic range. Equation 25 converts RMS noise to effective resolution.

Equation 13. Dynamic Range (dB) = 20 · log10[FSR / (2 · √2 · en)]
Equation 14. Effective Resolution (bits) = log2(FSR / en)

where:

  • FSR = 2 · VREF (1x input range)
  • FSR = 4 · VREF (2x input range)
  • en = Noise voltage (RMS)

When evaluating ADC noise performance, consider the effect of the external buffer and amplifier noise to the total noise performance. The noise performance of the ADC is evaluated in isolation of the amplifiers by selecting the input short test connection of the input multiplexer.

Table 6-1 Wideband Filter Noise Performance (VREF = 4.096V, 1x Input Range)
MODEfCLK
(MHz)
OSRDATA RATE
(kSPS)
NOISE
(en, µVRMS)
DYNAMIC RANGE
(dB)
EFFECTIVE RESOLUTION
(Bits)
Max speed32.7683251211.1108.319.5
High speed25.640010.9108.519.5
Mid speed12.820010.6108.719.6
Low speed3.25010.4108.919.6
Max speed32.768642567.64111.620.0
High speed25.62007.50111.720.1
Mid speed12.81007.30112.020.1
Low speed3.2257.14112.220.1
Max speed32.7681281285.34114.720.5
High speed25.61005.25114.820.6
Mid speed12.8505.07115.120.6
Low speed3.212.54.97115.320.7
Max speed32.768256643.79117.721.0
High speed25.6503.72117.821.1
Mid speed12.8253.58118.221.1
Low speed3.26.253.53118.321.1
Max speed32.768512322.71120.621.5
High speed25.6252.67120.721.5
Mid speed12.812.52.54121.221.6
Low speed3.23.1252.47121.421.7
Max speed32.7681024161.88123.822.1
High speed25.612.51.87123.822.1
Mid speed12.86.251.82124.022.1
Low speed3.21.56251.76124.322.2
Max speed32.768204881.34126.722.5
High speed25.66.251.32126.822.5
Mid speed12.83.1251.29127.022.6
Low speed3.20.781251.25127.322.6
Max speed32.768409640.96129.623.0
High speed25.63.1250.95129.723.0
Mid speed12.81.56250.93129.923.1
Low speed3.20.3906250.89130.323.1
Table 6-2 Sinc3 and Sinc4 Filter Noise Performance (VREF = 4.096V, 1x Input Range)
MODEfCLK
(MHz)
OSRDATA RATE
(kSPS)
NOISE
(en, µVRMS)(1)
DYNAMIC RANGE
(dB)
EFFECTIVE RESOLUTION (Bits)
SINC3SINC4SINC3SINC4SINC3SINC4
Max speed32.768121365.323966.881.792.715.116.9
High speed25.61066.623566.681.892.815.116.9
Mid speed12.8533.323563.881.893.115.117.0
Low speed3.2133.3323263.181.993.215.117.0
Max speed32.76816102499.924.889.2101.316.318.3
High speed25.680099.624.589.3101.516.318.4
Mid speed12.840098.924.589.3101.516.318.4
Low speed3.210096.024.389.6101.516.418.4
Max speed32.76824682.6731.110.899.4108.618.019.5
High speed25.6533.331.010.399.4108.918.019.6
Mid speed12.8266.6730.810.199.5109.218.019.6
Low speed3.266.6730.79.9699.5109.318.019.6
Max speed32.7683251215.28.24105.6110.919.019.9
High speed25.640015.08.07105.7111.119.120.0
Mid speed12.820014.87.88105.8111.319.120.0
Low speed3.25014.77.76105.9111.419.120.0
Max speed32.768642566.205.71113.4114.120.320.5
High speed25.62006.155.53113.5114.420.320.5
Mid speed12.81005.985.42113.7114.620.420.5
Low speed3.2255.785.24114.0114.920.420.6
Max speed32.7681281284.213.98116.8117.220.921.0
High speed25.61004.163.89116.9117.420.921.0
Mid speed12.8504.103.75117.0117.820.921.1
Low speed3.212.53.993.72117.2117.821.021.1
Mid speed12.816738.3233.563.39118.2118.621.121.2
Max speed32.768256642.992.78119.7120.421.421.5
High speed25.6502.952.74119.8120.521.421.5
Mid speed12.8252.872.69120.1120.621.421.5
Low speed3.26.252.812.61120.3120.921.521.6
Max speed32.76833349.2012.672.50120.7121.321.521.6
High speed25.638.4382.592.46121.0121.421.621.7
Mid speed12.819.2192.532.43121.2121.521.621.7
Low speed3.24.8042.462.33121.4121.921.721.7
Max speed32.768512322.111.98122.8123.321.922.0
High speed25.6252.091.93122.8123.521.922.0
Mid speed12.812.52.011.88123.2123.822.022.1
Low speed3.23.1251.961.67123.4124.822.022.2
Max speed32.76866724.5641.901.77123.7124.322.022.1
High speed25.619.191.861.75123.8124.422.122.2
Mid speed12.89.5951.821.67124.0124.822.122.2
Low speed3.22.391.771.65124.3124.922.122.2
Max speed32.7681024161.501.41125.7126.322.422.5
High speed25.612.51.471.40125.9126.322.422.5
Mid speed12.86.251.431.34126.1126.722.422.5
Low speed3.21.561.421.31126.2126.922.522.6
Max speed32.768133312.2911.361.25126.6127.322.522.6
High speed25.69.6021.341.23126.7127.422.522.7
Mid speed12.84.8011.291.19127.0127.722.622.7
Low speed3.21.21.241.17127.4127.922.722.7
Max speed32.768204881.061.00128.7129.222.923.0
High speed25.66.251.050.995128.8129.322.923.0
Mid speed12.83.1251.020.952129.1129.722.923.0
Low speed3.20.780.9690.935129.5129.823.023.1
Max speed32.76826676.1430.9670.890129.5130.323.023.1
High speed25.64.7990.9490.858129.7130.623.023.2
Mid speed12.82.40.9130.867130.0130.523.123.2
Low speed3.20.60.9140.844130.0130.723.123.2
Max speed32.768409640.7510.710131.7132.223.423.5
High speed25.63.1250.7520.709131.7132.223.423.5
Mid speed12.81.5630.7250.681132.0132.623.423.5
Low speed3.20.390.7090.649132.2133.023.523.6
Max speed32.76853333.0720.6970.630132.4133.323.523.6
High speed25.62.40.6760.626132.6133.323.523.6
Low speed3.20.30.6610.604132.8133.623.623.7
Mid speed12.8133330.4370.4100.60136.3137.024.224.3
Mid speed12.8160000.4000.3920.356137.4138.224.324.5
Max speed32.768266670.6140.3350.320138.7139.424.524.6
High speed25.60.4800.3300.311138.9139.124.624.7
Low speed3.20.060.3160.290139.2140.024.724.8
Max speed32.768320000.5120.3090.303139.4139.624.724.7
High speed25.60.40.3060.294139.5139.924.724.7
Low speed3.20.050.2900.275140.0140.524.824.8
Mid speed12.8480000.1330.2510.274141.2140.525.024.8
Mid speed12.8800000.080.2330.208141.9142.925.125.2
Max speed32.768960000.170670.2380.202141.7143.125.025.3
High speed25.60.1330.1860.250143.8141.325.425.0
Low speed3.20.01670.2450.207141.5142.925.025.2
Max speed32.7681600000.1020.2430.243141.5141.525.025.0
High speed25.60.080.2320.242141.9141.625.125.0
Low speed3.20.010.2430.177141.5144.325.025.5
High OSR values can yield varying noise results because of the limits of 24-bit quantization: 4.096 V / 223 = 0.488μV / code.
Table 6-3 Sinc3 + Sinc1 and Sinc4 + Sinc1 Filter Noise Performance (VREF = 4.096V, 1x Input Range)
MODEfCLK
(MHz)
OSR
DATA RATE
(SPS)
NOISE
(en, µVRMS)(1)
DYNAMIC RANGE
(dB)
EFFECTIVE RESOLUTION (Bits)
Mid speed12.8133334800.573134.123.8
Mid speed12.8160004000.533134.723.9
Max speed32.768266566140.419136.824.2
High speed25.64800.416136.924.2
Low speed3.2600.413136.924.2
Max speed32.768320005120.409137.024.3
High speed25.64000.387137.524.3
Low speed3.2500.362138.124.4
Mid speed12.8480001330.321139.124.6
Mid speed12.880000800.274140.524.8
Max speed32.76896000170.60.254141.124.9
High speed25.61330.256141.124.9
Low speed3.216.70.251141.225.0
Max speed32.768160000102.440.202143.125.3
High speed25.6800.187143.825.4
Low speed3.2100.201143.225.3
High OSR values can yield varying noise results because of the limits of 24-bit quantization: 4.096V / 223 = 0.488μV / code. Sinc3 + sinc1 and sinc4 + sinc1 filters yield equal noise performance.
Table 6-4 FIR1 Filter Noise Performance (VREF = 4.096V, 1x Input Range)
MODEfCLK
(MHz)
OSRDATA RATE
(kSPS)
NOISE
(en, µVRMS)
DYNAMIC RANGE
(dB)
EFFECTIVE RESOLUTION
(Bits)
Max speed32.7688204864173.113.6
High speed25.6160064873.013.6
Mid speed12.880066272.813.6
Low speed3.220068172.613.6
Max speed32.76816102493.089.916.4
High speed25.680094.889.716.4
Mid speed12.840099.989.216.3
Low speed3.210010588.816.2
Max speed32.7683251211.0108.419.5
High speed25.640010.8108.619.5
Mid speed12.820010.5108.819.6
Low speed3.25010.3109.019.6
Max speed32.768642567.44111.820.1
High speed25.62007.30112.020.1
Mid speed12.81007.09112.220.1
Low speed3.2256.93112.420.2
Max speed32.7681281285.20114.920.6
High speed25.61005.10115.120.6
Mid speed12.8504.93115.420.7
Low speed3.212.54.82115.620.7
Max speed32.768256643.69117.921.1
High speed25.6503.63118.021.1
Mid speed12.8253.48118.421.2
Low speed3.26.253.39118.621.2
Max speed32.768512322.64120.821.6
High speed25.6252.62120.921.6
Mid speed12.812.52.47121.421.7
Low speed3.23.1251.27127.122.6
Max speed32.7681024161.94123.522.0
High speed25.612.51.90123.622.0
Mid speed12.86.251.76124.322.2
Low speed3.21.56250.886130.323.1
Table 6-5 FIR2 Filter Performance (VREF = 4.096V, 1x Input Range)
MODEfCLK
(MHz)
OSRDATA RATE
(kSPS)
NOISE
(en, µVRMS)
DYNAMIC RANGE
(dB)
EFFECTIVE RESOLUTION
(Bits)
Max speed32.76816102451.095.117.3
High speed25.680051.095.117.3
Mid speed12.840050.395.217.3
Low speed3.210050.095.317.3
Max speed32.7683251211.6108.019.4
High speed25.640011.4108.119.5
Mid speed12.820011.1108.319.5
Low speed3.25010.9108.519.5
Max speed32.768642567.85111.320.0
High speed25.62007.69111.520.0
Mid speed12.81007.47111.821.1
Low speed3.2257.33111.921.1
Max speed32.7681281285.47114.520.5
High speed25.61005.36114.720.5
Mid speed12.8505.18114.920.6
Low speed3.212.55.07115.120.6
Max speed32.768256643.86117.521.0
High speed25.6503.80117.621.0
Mid speed12.8253.66118.021.1
Low speed3.26.253.58118.221.1
Max speed32.768512322.79120.321.5
High speed25.6252.73120.521.5
Mid speed12.812.52.59121.021.6
Low speed3.23.1251.76124.322.2
Max speed32.7681024162.01123.222.0
High speed25.612.51.99123.322.0
Mid speed12.86.251.83124.022.1
Low speed3.21.56251.26127.222.6
Max speed32.768204881.51125.622.4
High speed25.66.251.48125.822.4
Mid speed12.83.1250.928129.923.1
Low speed3.20.781250.927129.923.1