JAJSHV5B June   2017  – August 2019 ADS1287

PRODUCTION DATA.  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
    1.     Device Images
      1.      機能ブロック図
  4. 4 改訂履歴
  5. 5 概要（続き）
  6. 6 Pin Configuration and Functions
    1.     Pin Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Requirements
    7. 7.7 Switching Characteristics
    8. 7.8 Typical Characteristics
  8. 8 Parameter Measurement Information
    1. 8.1 Noise Performance
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Analog Input and Multiplexer
      2. 9.3.2 Programmable Gain Amplifier (PGA)
      3. 9.3.3 Modulator
        1. 9.3.3.1 Modulator Overrange
      4. 9.3.4 Voltage Reference Inputs (REFP, REFN)
      5. 9.3.5 Digital Filter
        1. 9.3.5.1 Sinc Filter Stage
        2. 9.3.5.2 FIR Filter Stage
        3. 9.3.5.3 Group Delay and Step Response
          1. 9.3.5.3.1 Linear Phase Response
          2. 9.3.5.3.2 Minimum Phase Response
        4. 9.3.5.4 HPF Stage
      6. 9.3.6 Reset (RESET Pin and Reset Command)
      7. 9.3.7 Master Clock Input (CLK)
    4. 9.4 Device Functional Modes
      1. 9.4.1  Operational Mode
      2. 9.4.2  Chop Mode
      3. 9.4.3  Offset
      4. 9.4.4  Power-Down Mode
      5. 9.4.5  Standby Mode
      6. 9.4.6  Synchronization
        1. 9.4.6.1 Pulse-Sync Mode
        2. 9.4.6.2 Continuous-Sync Mode
      7. 9.4.7  Reading Data
        1. 9.4.7.1 Read-Data-Continuous Mode (RDATAC)
        2. 9.4.7.2 Stop-Read-Data-Continuous-Mode (SDATAC)
      8. 9.4.8  Conversion Data Format
      9. 9.4.9  Offset and Full-Scale Calibration Registers
        1. 9.4.9.1 OFC[2:0] Registers
        2. 9.4.9.2 FSC[2:0] Registers
      10. 9.4.10 Calibration Command
        1. 9.4.10.1 OFSCAL Command
        2. 9.4.10.2 GANCAL Command
      11. 9.4.11 User Calibration
    5. 9.5 Programming
      1. 9.5.1 Serial Interface
        1. 9.5.1.1 Chip Select (CS)
        2. 9.5.1.2 Serial Clock (SCLK)
        3. 9.5.1.3 Data Input (DIN)
        4. 9.5.1.4 Data Output (DOUT)
        5. 9.5.1.5 Serial Interface Timeout
        6. 9.5.1.6 Data Ready (DRDY)
      2. 9.5.2 Commands
        1. 9.5.2.1  WAKEUP: Wake Up Command
        2. 9.5.2.2  STANDBY: Standby Mode Command
        3. 9.5.2.3  SYNC: Synchronize ADC Conversions
        4. 9.5.2.4  RESET: Reset Command
        5. 9.5.2.5  RDATAC: Read Data Continuous Mode Command
        6. 9.5.2.6  SDATAC: Stop Read Data Continuous Mode Command
        7. 9.5.2.7  RDATA: Read Data Command
        8. 9.5.2.8  RREG: Read Register Data Command
        9. 9.5.2.9  WREG: Write Register Data Command
        10. 9.5.2.10 OFSCAL: Offset Calibration Command
        11. 9.5.2.11 GANCAL: Gain Calibration Command
    6. 9.6 Register Map
      1. 9.6.1 Register Descriptions
        1. 9.6.1.1 ID/CFG: ID, Configuration Register (address = 00h) [reset = x0h]
          1. Table 22. ID/CFG Register Field Descriptions
        2. 9.6.1.2 CONFIG0: Configuration Register 0 (address = 01h) [reset = 52h]
          1. Table 23. CONFIG0 Register Field Descriptions
        3. 9.6.1.3 CONFIG1: Configuration Register 1 (address = 02h) [reset = 08h]
          1. Table 24. CONFIG1 Register Field Descriptions
        4. 9.6.1.4 High-Pass Filter Corner Frequency (HPFx) Registers (address = 03h, 04h) [reset = 32h, 03h]
          1. Table 25. HPF0, HPF1 Registers Field Description
        5. 9.6.1.5 Offset Calibration (OFCx) Registers (address = 05h, 06h, 07h) [reset = 00h, 00h, 00h]
          1. Table 26. OFC0, OFC1, OFC2 Registers Field Description
        6. 9.6.1.6 Full-Scale Calibration (FSCx) Registers (address = 08h, 09h, 0Ah) [reset = 00h, 00h, 40h]
          1. Table 27. FSC0, FSC1, FSC2 Registers Field Description
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Applications
      1. 10.2.1 Geophone Application
      2. 10.2.2 Digital Interface
    3. 10.3 Initialization Set Up
  11. 11Power Supply Recommendations
    1. 11.1 Analog Power Supplies
    2. 11.2 Digital Power Supply
    3. 11.3 Power-Supply Sequence
  12. 12Layout
    1. 12.1 Layout Guidelines
  13. 13デバイスおよびドキュメントのサポート
    1. 13.1 ドキュメントの更新通知を受け取る方法
    2. 13.2 コミュニティ・リソース
    3. 13.3 商標
    4. 13.4 静電気放電に関する注意事項
    5. 13.5 Glossary
  14. 14メカニカル、パッケージ、および注文情報

パッケージ・オプション

デバイスごとのパッケージ図は、PDF版データシートをご参照ください。

メカニカル・データ（パッケージ｜ピン）
  • RHF|24
サーマルパッド・メカニカル・データ
発注情報

10.2.1 Geophone Application

Figure 79 illustrates a typical geophone application circuit. The application shows the ADC operating on a bipolar ±2.5-V analog supply voltage. The power-supply voltages are provided by low-dropout (LDO) regulators to provide well-regulated, low-noise supply voltages to the ADC. The ADC also operates using with a unipolar 5-V analog supply voltage. The 6-V zener diode between AVDD and AVSS clamps the ADC supply voltage if the inputs are driven when the ADC supply voltage is off.

Resistors R1 and R2 bias the floating geophone to mid-supply. The resistors also provide a return path for the ADC input current. To prevent pickup of PCB ground-related noise, connect the resistors together first, then connect to ground. For unipolar-supply operation, make this connection to a low-impedance 2.5-V voltage.

The geophone signal is filtered both differentially, by components C3 and R3 through R6, and common-mode filtered by components C1, C2 and R3, R4. The differential filter removes normal-mode noise. The common-mode filters remove noise that is common to both inputs. The differential filter high-cut frequency is 10 times lower to minimize the effects of component mismatch of the common-mode filter that otherwise can lead to degraded differential-filter performance. Adjust the filter components according to the application requirements. The protection diodes protect the ADC inputs from system-level ESD transients and signal overrange events.

A low-noise, low-power, 2.5-V voltage reference drives the ADC reference input. The voltage reference ground terminal is connected to –2.5 V. R9 and C5 form an optional 2-Hz noise filter to reduce voltage reference noise. Capacitor C6 filters the reference sampling glitches. Place the capacitor directly at the ADC pins. Multiple ADCs can share a single reference but place a 0.1-µF capacitor at each ADC reference input.

Capacitor C4 (10 nF), located at the CAPP and CAPN pins, filters modulator sampling glitches. The capacitor also provides a antialiasing filter with a high cutoff corner frequency of approximately 9.5 kHz. Resistors R7 and R8 provide an offset voltage to the modulator for idle tone reduction when operating in high-resolution mode. Use the internal offset in low-power mode operation. The resistors are not needed in this case.

ADS1287 ai_iface_geophone_sbas778.gifFigure 79. Geophone Analog Interface