SBASB68 August   2025 ADS9803

PRODMIX  

  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
    7. 5.7 Switching Characteristics
    8. 5.8 Timing Diagrams
    9. 5.9 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Analog Inputs
        1. 6.3.1.1 Input Clamp Protection Circuit
        2. 6.3.1.2 Programmable Gain Amplifier (PGA)
        3. 6.3.1.3 Wide-Common-Mode Voltage Rejection Circuit
      2. 6.3.2 ADC Transfer Function
      3. 6.3.3 ADC Sampling Clock Input
      4. 6.3.4 Synchronizing Multiple ADCs
      5. 6.3.5 Reference Voltage
      6. 6.3.6 Data Interface
        1. 6.3.6.1 Data Clock Output
        2. 6.3.6.2 ADC Output Data Randomizer
        3. 6.3.6.3 Data Averaging
        4. 6.3.6.4 Test Patterns for Data Interface
          1. 6.3.6.4.1 Fixed Pattern
          2. 6.3.6.4.2 Digital Ramp
          3. 6.3.6.4.3 Alternating Test Pattern
    4. 6.4 Device Functional Modes
      1. 6.4.1 Reset
      2. 6.4.2 Power-Down
      3. 6.4.3 Initialization Sequence
      4. 6.4.4 Normal Operation
      5. 6.4.5 Speed-Boost Mode
    5. 6.5 Programming
      1. 6.5.1 Register Write
      2. 6.5.2 Register Read
      3. 6.5.3 Multiple Devices in a Daisy-Chain Topology for SPI Configuration
        1. 6.5.3.1 Register Write With Daisy-Chain
        2. 6.5.3.2 Register Read With Daisy-Chain
  8. 7 Register Map
    1. 7.1 Register Bank 0
    2. 7.2 Register Bank 1
    3. 7.3 Register Bank 2
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Parametric Measurement Unit (PMU)
      2. 8.2.2 Design Requirements
      3. 8.2.3 Detailed Design Procedure
      4. 8.2.4 Application Curve
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Receiving Notification of Documentation Updates
    2. 9.2 Support Resources
    3. 9.3 Trademarks
    4. 9.4 Electrostatic Discharge Caution
    5. 9.5 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

Package Options

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

6.3.1.3 Wide-Common-Mode Voltage Rejection Circuit

The ADS9803 features a common-mode (CM) rejection circuit at the analog inputs that supports CM voltages up to ±12V. The CM voltage for differential inputs is given by Equation 1. On power-up or after reset, the common-mode voltage range for the analog input channels is ±12V (CM_CTRL_EN = 0b). In all cases, verify the voltage at the analog inputs is within the Absolute Maximum Ratings.

Equation 1. C o m m o n   m o d e   v o l t a g e =   ( Voltage on AINP ) + ( Voltage on AINM ) 2

As described in Table 6-3, optimize the CM voltage rejection circuit for various CM voltages for differential inputs.

Table 6-3 Wide Common-Mode Configuration for Differential Inputs
COMMON-MODE (CM) RANGE CM_CTRL_EN ANALOG INPUT CHANNELS 1–4 ANALOG INPUT CHANNELS 5–8
CM_EN_CH[4:1] CM_RNG_CH[4:1] CM_EN_CH[8:5] CM_RNG_CH[8:5]
CM ≤ ±1V 1 0 Don't care 0 Don't care
CM ≤ ±RANGE / 2 1 0 1 0
CM ≤ ±6V 1 1
CM ≤ ±12V 2 2

The CM voltage rejection circuit is configured depending on the analog input range of the PGA when using single-ended inputs. Table 6-4 lists the recommended configuration for single-ended inputs for various analog input voltage ranges.

Table 6-4 Wide Common-Mode Configuration for Single-Ended Inputs
PGA ANALOG INPUT RANGE CM_CTRL_EN ANALOG INPUT CHANNELS 1–4 ANALOG INPUT CHANNELS 5–8
CM_EN_CH[4:1] CM_RNG_CH[4:1] CM_EN_CH[8:5] CM_RNG_CH[8:5]
±2.5V, ±3.5V, and ±5V 1 0 Don't care 0 Don't care
±7V, ±10V, and ±12V 1 0 1 0

Typical SNR for analog input ranges vs input common-mode ranges are shown in Table 6-5 for low-bandwidth mode and Table 6-6 for wide-bandwidth mode.

Table 6-5 Typical SNR (dBFS) for Analog Input Range vs Common-Mode Range in Low-Bandwidth Mode
RANGE CM ≤ ±1V CM ≤ ±RANGE / 2 CM ≤ ±6V CM ≤ ±12V
±2.5V 88.3 87.4 85.2 83.4
±3.5V 88.3 88.4 87.0 85.4
±5V 90.1 89.1 88.4 87.2
±7V – 89.8 89.4 88.5
±10V – 90.2 90.2 89.5
±12V – 90.3 90.3 89.9
Table 6-6 Typical SNR (dBFS) for Analog Input Range vs Common-Mode Range in Wide-Bandwidth Mode
RANGE CM ≤ ±1V CM ≤ ±RANGE / 2 CM ≤ ±6V CM ≤ ±12V
±2.5V 80.5 79.1 76.7 74.7
±3.5V 81.1 79.4 77.6 75.8
±5V 81.6 79.7 78.4 76.7
±7V – 80.0 79.2 77.5
±10V – 81.6 81.2 79.7
±12V – 82.4 82.4 80.9