SBAS989 April   2019 PCM1840

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Simplified Block Diagram
  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: TDM, I2S or LJ Interface
    7. 6.7 Switching Characteristics: TDM, I2S or LJ Interface
    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 Hardware Control
      2. 7.3.2 Audio Serial Interfaces
        1. 7.3.2.1 Time Division Multiplexed Audio (TDM) Interface
        2. 7.3.2.2 Inter IC Sound (I2S) Interface
        3. 7.3.2.3 Left-Justified (LJ) Interface
      3. 7.3.3 Phase-Locked Loop (PLL) and Clock Generation
      4. 7.3.4 Input Channel Configurations
      5. 7.3.5 Reference Voltage
      6. 7.3.6 Microphone Bias
      7. 7.3.7 Signal-Chain Processing
        1. 7.3.7.1 Digital High-Pass Filter
        2. 7.3.7.2 Configurable Digital Decimation Filters
          1. 7.3.7.2.1 Linear Phase Filters
            1. 7.3.7.2.1.1 Sampling Rate: 8 kHz or 7.35 kHz
            2. 7.3.7.2.1.2 Sampling Rate: 16 kHz or 14.7 kHz
            3. 7.3.7.2.1.3 Sampling Rate: 24 kHz or 22.05 kHz
            4. 7.3.7.2.1.4 Sampling Rate: 32 kHz or 29.4 kHz
            5. 7.3.7.2.1.5 Sampling Rate: 48 kHz or 44.1 kHz
            6. 7.3.7.2.1.6 Sampling Rate: 96 kHz or 88.2 kHz
            7. 7.3.7.2.1.7 Sampling Rate: 192 kHz or 176.4 kHz
          2. 7.3.7.2.2 Low-Latency Filters
            1. 7.3.7.2.2.1 Sampling Rate: 16 kHz or 14.7 kHz
            2. 7.3.7.2.2.2 Sampling Rate: 24 kHz or 22.05 kHz
            3. 7.3.7.2.2.3 Sampling Rate: 32 kHz or 29.4 kHz
            4. 7.3.7.2.2.4 Sampling Rate: 48 kHz or 44.1 kHz
            5. 7.3.7.2.2.5 Sampling Rate: 96 kHz or 88.2 kHz
      8. 7.3.8 Dynamic Range Enhancer (DRE)
    4. 7.4 Device Functional Modes
      1. 7.4.1 Hardware Shutdown
      2. 7.4.2 Active Mode
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Receiving Notification of Documentation Updates
    2. 11.2 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

7.3.8 Dynamic Range Enhancer (DRE)

The device integrates an ultra-low noise front-end DRE gain amplifier with 123-dB dynamic range performance with a low-noise, low-distortion, multibit delta-sigma (ΔΣ) ADC with a 108-dB dynamic range. The dynamic range enhancer (DRE) is a digitally assisted algorithm to boost the overall channel performance. The DRE monitors the incoming signal amplitude and accordingly adjusts the internal DRE amplifier gain automatically. The DRE achieves a complete-channel dynamic range as high as 123 dB. At a system level, the DRE scheme enables far-field, high-fidelity recording of audio signals in very quiet environments and low-distortion recording in loud environments.

The DRE can be enable only in slave mode by driving high to the MD1 pin. Table 20 shows the DRE selection for the record channel.

Table 20. DRE Selection for the Record Channel

MD1 DRE SELECTION (Supported Only in Slave Mode)
LOW DRE is disabled in slave mode. For master mode, DRE is always disabled.
HIGH DRE is enabled with DRE_LVL = –36 dB and DRE_MAXGAIN = 24 dB in slave mode. For master mode, DRE is always disabled.

This algorithm is implemented with very low latency and all signal chain blocks are designed to minimize any audible artifacts that may occur resulting from dynamic gain modulation. The target signal threshold level, DRE_LVL, at which DRE is triggered is fixed to the –36-dB input signal level. The DRE gain range can be dynamically modulated by using DRE_MAXGAIN, which is fixed to 24 dB to maximize the benefit of the DRE in real-world applications and to minimize any audible artifacts.

Enabling the DRE for processing increases the power consumption of the device because of increased signal processing. Therefore, disable the DRE for low-power critical applications. Furthermore, the DRE is not supported for output sample rates greater than 48 kHz.