SBAS707B June   2016  – January 2018 ADS8910B , ADS8912B , ADS8914B

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Ease of System Design With ADS89xxB Integrated Features
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Timing Requirements
    7. 6.7 Switching Characteristics
    8. 6.8 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 LDO Module
      2. 7.3.2 Reference Buffer Module
      3. 7.3.3 Converter Module
        1. 7.3.3.1 Sample-and-Hold Circuit
        2. 7.3.3.2 Internal Oscillator
        3. 7.3.3.3 ADC Transfer Function
      4. 7.3.4 Interface Module
    4. 7.4 Device Functional Modes
      1. 7.4.1 RST State
      2. 7.4.2 ACQ State
      3. 7.4.3 CNV State
    5. 7.5 Programming
      1. 7.5.1 Output Data Word
      2. 7.5.2 Data Transfer Frame
      3. 7.5.3 Interleaving Conversion Cycles and Data Transfer Frames
      4. 7.5.4 Data Transfer Protocols
        1. 7.5.4.1 Protocols for Configuring the Device
        2. 7.5.4.2 Protocols for Reading From the Device
          1. 7.5.4.2.1 Legacy, SPI-Compatible (SYS-xy-S) Protocols
          2. 7.5.4.2.2 SPI-Compatible Protocols with Bus Width Options
          3. 7.5.4.2.3 Source-Synchronous (SRC) Protocols
            1. 7.5.4.2.3.1 Output Clock Source Options with SRC Protocols
            2. 7.5.4.2.3.2 Bus Width Options With SRC Protocols
            3. 7.5.4.2.3.3 Output Data Rate Options With SRC Protocols
      5. 7.5.5 Device Setup
        1. 7.5.5.1 Single Device: All multiSPI Options
        2. 7.5.5.2 Single Device: Minimum Pins for a Standard SPI Interface
        3. 7.5.5.3 Multiple Devices: Daisy-Chain Topology
        4. 7.5.5.4 Multiple Devices: Star Topology
    6. 7.6 Register Maps
      1. 7.6.1 Device Configuration and Register Maps
        1. 7.6.1.1 PD_CNTL Register (address = 04h) [reset = 00h]
          1. Table 11. PD_CNTL Register Field Descriptions
        2. 7.6.1.2 SDI_CNTL Register (address = 008h) [reset = 00h]
          1. Table 12. SDI_CNTL Register Field Descriptions
        3. 7.6.1.3 SDO_CNTL Register (address = 0Ch) [reset = 00h]
          1. Table 13. SDO_CNTL Register Field Descriptions
        4. 7.6.1.4 DATA_CNTL Register (address = 010h) [reset = 00h]
          1. Table 14. DATA_CNTL Register Field Descriptions
        5. 7.6.1.5 PATN_LSB Register (address = 014h) [reset = 00h]
          1. Table 15. PATN_LSB Register Field Descriptions
        6. 7.6.1.6 PATN_MID Register (address = 015h) [reset = 00h]
          1. Table 16. PATN_MID Register Field Descriptions
        7. 7.6.1.7 PATN_MSB Register (address = 016h) [reset = 00h]
          1. Table 17. PATN_MSB Register Field Descriptions
        8. 7.6.1.8 OFST_CAL Register (address = 020h) [reset = 00h]
          1. Table 18. OFST_CAL Register Field Descriptions
        9. 7.6.1.9 REF_MRG Register (address = 030h) [reset = 00h]
          1. Table 19. REF_MRG Register Field Descriptions
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 ADC Reference Driver
      2. 8.1.2 ADC Input Driver
        1. 8.1.2.1 Charge-Kickback Filter
        2. 8.1.2.2 Input Amplifier Selection
    2. 8.2 Typical Application
      1. 8.2.1 Data Acquisition (DAQ) Circuit for Lowest Distortion and Noise Performance With Differential Input
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curves
      2. 8.2.2 DAQ Circuit With FDA Input Driver and Single-Ended or Differential Input
      3. 8.2.3 Design Requirements
      4. 8.2.4 Detailed Design Procedure
      5. 8.2.5 Application Curves
  9. 9 Power-Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Signal Path
      2. 10.1.2 Grounding and PCB Stack-Up
      3. 10.1.3 Decoupling of Power Supplies
      4. 10.1.4 Reference Decoupling
      5. 10.1.5 Differential Input Decoupling
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Related Links
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Community Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8.2.4 Detailed Design Procedure

The application circuits are shown in Figure 108 and Figure 109. In both applications, the input signal is processed through a high-bandwidth, low-distortion, fully-differential amplifier (FDA) designed in a gain of 1 V/V and a low-pass RC filter before going to the ADC.

The reference voltage of 4.5 V generated by the high-precision, low-noise REF5045 circuit. The output broadband noise of the reference is heavily filtered by a low-pass filter with a 3-dB cutoff frequency of 16 Hz.

Generally, the distortion from the input driver must be at least 10 dB less than the ADC distortion. The distortion resulting from variation in the common-mode signal is eliminated by using the FDA in an inverting gain configuration that establishes a fixed common-mode level for the circuit. This configuration also eliminates the requirement of a rail-to-rail swing at the amplifier input. Therefore, these circuits use the low-power THS4551 as an input driver that provides exceptional ac performance because of its extremely low-distortion and high bandwidth specifications. In addition, the components of the charge kickback filter keep the noise from the front-end circuit low without adding distortion to the input signal.

The circuit in Figure 108 shows a fully-differential data acquisition (DAQ) block optimized for low distortion and noise using the THS4551 and ADS891xB. This front-end circuit configuration requires a differential signal at the input of the FDA and provides a differential output to drive the ADC inputs. The common-mode voltage of the input signal provided to the ADC is set by the VOCM pin of the THS4551 (not shown in Figure 108). To use the complete dynamic range of the ADC, VOCM can be set to VREF / 2 by using a simple resistive divider.

The circuit in Figure 109 shows a single-ended to differential DAQ block optimized for low distortion and noise using the THS4551 and the ADS891xB. This front-end circuit configuration requires a single-ended bipolar signal at the input of the FDA and provides a fully-differential output to drive the ADC inputs. The common-mode voltage of the input signal provided to the ADC is set by the VOCM pin of the THS4551 (not shown in Figure 109). To use the complete dynamic range of the ADC, VOCM can be set to VREF / 2 by using a simple resistive divider.