SBASB74 October   2024 ADS127L21B

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 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. 6 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. 7 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. 8 Register Map
  10. 9 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

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information
7.3.5.2.1 Sinc3 and Sinc4 Filters

The sinc filter averages and decimates the high-speed modulator data to produce high-resolution output data at reduced data rate. Increasing the OSR value decreases the data rate and simultaneously reduces signal bandwidth and conversion noise resulting from increased decimation and data averaging. Table 7-14 lists the sinc3 and sinc4 filter –3dB frequency and latency time.

Table 7-9 Sinc3 and Sinc4 Filter Characteristics
MODEfCLK
(MHz)		OSR DATA RATE
(kSPS)		–3dB FREQUENCY (kHz)LATENCY TIME(1) (μs)
SINC3SINC4SINC3SINC4
Max speed32.768121365.3357.0310.22.973.66
High speed25.61066.6278.9242.33.734.69
Mid speed12.8533.3139.5121.27.469.36
Low speed3.2133.3334.930.329.837.4
Max speed32.768161024267.8232.73.664.63
High speed25.6800209.2181.84.675.95
Mid speed12.8400104.690.99.3311.9
Low speed3.210026.222.737.447.3
Max speed32.76824682.67178.5155.15.126.64
High speed25.6533.3139.5121.26.578.43
Mid speed12.8266.6769.760.613.116.9
Low speed3.266.6717.415.152.367.4
Max speed32.76832512133.9116.36.598.55
High speed25.6400104.690.98.4210.9
Mid speed12.820052.345.416.921.8
Low speed3.25013.111.467.387.2
Max speed32.7686425666.958.212.416.4
High speed25.620052.345.416.021.0
Mid speed12.810026.222.731.841.9
Low speed3.2256.545.68127167
Max speed32.76812812833.529.124.232.0
High speed25.610026.222.731.041.0
Mid speed12.85013.111.461.981.9
Low speed3.212.53.272.84247327
Mid speed12.816738.32310.08.7180.2106
Max speed32.7682566416.714.547.663.2
High speed25.65013.111.460.980.9
Mid speed12.8256.545.68121.9162
Low speed3.26.251.631.42487648
Max speed32.76833349.20112.911.261.782.0
High speed25.638.43810.18.7379.0105
Mid speed12.819.2195.034.37158210
Low speed3.24.8041.261.09631840
Max speed32.768512328.377.2794.5126
High speed25.6256.545.68121161
Mid speed12.812.53.272.84242322
Low speed3.23.1250.8170.7109671287
Max speed32.76866724.5646.425.58123164
High speed25.619.195.024.36157209
Mid speed12.89.5952.512.18314419
Low speed3.22.390.6270.54512581675
Max speed32.7681024164.183.64188251
High speed25.612.53.272.84241321
Mid speed12.86.251.631.42482642
Low speed3.21.56250.4090.35519272567
Max speed32.768133312.2913.212.79245326
High speed25.69.6022.512.18313417
Mid speed12.84.8011.261.09627835
Low speed3.21.20.3140.27325073340
Max speed32.768204882.091.82376501
High speed25.66.251.631.42481641
Mid speed12.83.1250.8170.7109621282
Low speed3.20.78130.2040.17838475127
Max speed32.76826676.1431.611.40489652
High speed25.64.7991.261.09626834
Mid speed12.82.40.6280.54512521669
Low speed3.20.60.1570.13650086675
Max speed32.768409641.0460.9097511001
High speed25.63.1250.8170.7109611281
Mid speed12.81.5630.4090.35519222562
Low speed3.20.3910.1020.089768710247
Max speed32.76853333.0720.8030.6989771303
High speed25.62.40.6280.54512511667
Low speed3.20.30.0780.0681000613340
Mid speed12.8133330.4800.1260.10962518335
Mid speed12.8160000.4000.1050.0909750110002
Max speed32.768266670.6140.1610.14048846511
High speed25.60.4800.1260.10962518334
Low speed3.20.060.01570.01365000866675
Max speed32.768320000.5120.1340.11658607813
High speed25.60.40.1050.091750110001
Low speed3.20.050.01310.01146000780007
Mid speed12.8480000.1330.03490.03032250230002
Mid speed12.8800000.080.02090.01823750250002
Max speed32.768960000.170670.04460.03881757923438
High speed25.60.1330.03490.03032250130001
Low speed3.20.01660.00440.0038180007240007
Max speed32.7681600000.1020.02680.02332929839063
High speed25.60.080.02090.01823750150001
Low speed3.20.010.00260.0023300005400004
(1) Latency time increases by 8 / fCLK (μs) when analog input buffers are enabled.

Because of the reduction of data averaging performed in the filtering process, the full 24 bits of output data are not available for OSR ≤ 24. Table 7-10 summarizes output resolution for OSR values ≤ 24.

Table 7-10 Sinc3 and Sinc4 Data Resolution
OSRRESOLUTION (Bits)
1219
1620.5
2423

Figure 7-24 and Figure 7-25 show the sinc filter frequency response. The frequency response consists of a series of response nulls occurring at fDATA and multiples thereof. At the null frequencies, the filter has zero gain. Figure 7-25 shows the folding of the frequency response starting at the fMOD / 2 frequency. No attenuation is provided by the filter at input frequencies near n · fMOD (n = 1, 2, 3, and so on).

ADS127L21B Sinc3 and Sinc4 Frequency Response (OSR = 32)Figure 7-24 Sinc3 and Sinc4 Frequency Response
(OSR = 32)
ADS127L21B Sinc4 Frequency Response to fMOD (OSR = 32)Figure 7-25 Sinc4 Frequency Response to fMOD (OSR = 32)

Table 7-11 shows the normal-mode rejection of the filter for data rates equal to common line-cycle frequencies.

Table 7-11 Normal-Mode Rejection
MODEOSRfDATA (SPS)2% CLOCK VARIATION6% CLOCK VARIATION
SINC3 FILTERSINC4 FILTERSINC3 FILTERSINC4 FILTER
Low-speed9600016.6100 dB135 dB72 dB95 dB
Low-speed3200050
Low-speed2666760
High-speed32000400