SNAS510S January   2011  – January 2016 LMP90097 , LMP90098 , LMP90099 , LMP90100

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Typical Application Schematic
  5. 5 Revision History
  6. 6 Description (continued)
  7. 7 Pin Configuration and Functions
  8. 8 Specifications
    1. 8.1  Absolute Maximum Ratings
    2. 8.2  ESD Ratings
    3. 8.3  Recommended Operating Conditions
    4. 8.4  Thermal Information
    5. 8.5  Electrical Characteristics
    6. 8.6  SPI Timing Requirements
    7. 8.7  CBS Setup and Hold Timing Requirements
    8. 8.8  SCLK and SDI Timing Requirements
    9. 8.9  SDO Timing Requirements
    10. 8.10 SDO and DRDYB Timing Requirements
    11. 8.11 Typical Characteristics
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 True Continuous Background Calibration
      2. 9.3.2 Continuous Background Sensor Diagnostics
      3. 9.3.3 Flexible Input MUX Channels
      4. 9.3.4 Programmable Gain Amplifiers (FGA and PGA)
      5. 9.3.5 Excitation Current Sources (IB1 and IB2) - LMP90100/LMP90098
      6. 9.3.6 Signal Path
        1. 9.3.6.1 Reference Input (VREF)
        2. 9.3.6.2 Flexible Input MUX (VIN)
        3. 9.3.6.3 Selectable Gains (FGA and PGA)
        4. 9.3.6.4 Buffer (BUFF)
        5. 9.3.6.5 Internal/External CLK Selection
        6. 9.3.6.6 Programmable ODRs
        7. 9.3.6.7 Digital Filter
        8. 9.3.6.8 GPIO (D0-D6)
      7. 9.3.7 Calibration
        1. 9.3.7.1 Background Calibration
          1. 9.3.7.1.1 Types of Background Calibration
          2. 9.3.7.1.2 Using Background Calibration
        2. 9.3.7.2 System Calibration
          1. 9.3.7.2.1 System Calibration Offset Coefficient Determination Mode
          2. 9.3.7.2.2 System Calibration Gain Coefficient Determination Mode
          3. 9.3.7.2.3 Post-Calibration Scaling
      8. 9.3.8 Sensor Interface
        1. 9.3.8.1 IB1 and IB2 - Excitation Currents
        2. 9.3.8.2 Burnout Currents
          1. 9.3.8.2.1 Burnout Current Injection
        3. 9.3.8.3 Sensor Diagnostic Flags
          1. 9.3.8.3.1 SHORT_THLD_FLAG
          2. 9.3.8.3.2 RAILS_FLAG
          3. 9.3.8.3.3 POR_AFT_LST_RD:
          4. 9.3.8.3.4 OFLO_FLAGS
          5. 9.3.8.3.5 SAMPLED_CH
      9. 9.3.9 RESET and RESTART
    4. 9.4 Device Functional Modes
      1. 9.4.1 Power Management
      2. 9.4.2 Channels Scan Mode
        1. 9.4.2.1 ScanMode0: Single-Channel Continuous Conversion
        2. 9.4.2.2 ScanMode1: Multiple-Channels Single Scan
        3. 9.4.2.3 ScanMode2: Multiple-Channels Continuous Scan
        4. 9.4.2.4 ScanMode3: Multiple-Channels Continuous Scan with Burnout Currents
    5. 9.5 Programming
      1. 9.5.1  General Rules
      2. 9.5.2  Serial Digital Interface
      3. 9.5.3  Register Address (ADDR)
      4. 9.5.4  Register Read/Write Protocol
      5. 9.5.5  Streaming
      6. 9.5.6  CSB - Chip Select Bar
      7. 9.5.7  SPI Reset
      8. 9.5.8  DRDYB - Data Ready Bar
      9. 9.5.9  DRDYB Case1: Combining SDO/DRDYB with SDO_DRDYB_DRIVER = 0x00
      10. 9.5.10 DRDYB Case2: Combining SDO/DRDYB with SDO_DRDYB_DRIVER = 0x03
      11. 9.5.11 DRDYB Case3: Routing DRDYB to D6
      12. 9.5.12 Data Only Read Transaction
      13. 9.5.13 Cyclic Redundancy Check (CRC)
      14. 9.5.14 Register Read/Write Examples
        1. 9.5.14.1 Writing To Register Examples
        2. 9.5.14.2 Reading From Register Example
      15. 9.5.15 Streaming Examples
        1. 9.5.15.1 Normal Streaming Example
        2. 9.5.15.2 Controlled Streaming Example
    6. 9.6 Register Maps
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Quick Start
      2. 10.1.2 ADC_DOUT Calculation
    2. 10.2 Typical Applications
      1. 10.2.1 3-Wire RTD Using 2 Current Sources
        1. 10.2.1.1 Design Requirements
        2. 10.2.1.2 Detailed Design Procedure
        3. 10.2.1.3 Application Curve
      2. 10.2.2 3-Wire RTD Using 1 Current Source
        1. 10.2.2.1 Design Requirements
        2. 10.2.2.2 Detailed Design Procedure
        3. 10.2.2.3 Application Curve
      3. 10.2.3 Thermocouple with Cold Junction Compensation
        1. 10.2.3.1 Design Requirements
        2. 10.2.3.2 Detailed Design Procedure
      4. 10.2.4 Application Curve
  11. 11Power Supply Recommendations
    1. 11.1 VA and VIO
    2. 11.2 VREF
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Device Support
      1. 13.1.1 Device Nomenclature
        1. 13.1.1.1 Specific Definitions
    2. 13.2 Related Links
    3. 13.3 Community Resources
    4. 13.4 Trademarks
    5. 13.5 Electrostatic Discharge Caution
    6. 13.6 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

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

11 Power Supply Recommendations

11.1 VA and VIO

Any ADC architecture is sensitive to spikes on the analog voltage, VA, digital input/output voltage, VIO, and ground pins. These spikes may originate from switching power supplies, digital logic, high power devices, and other sources. To diminish these spikes, the LMP90xxx’s VA and VIO pins should be clean and well bypassed. A 0.1 µF ceramic bypass capacitor and a 1 µF tantalum capacitor should be used to bypass the LMP90xxx supplies, with the 0.1 µF capacitor placed as close to the LMP90xxx as possible.

Because the LMP90xxx has both external VA and VIO pins, the user has two options on how to connect these pins. The first option is to tie VA and VIO together and power them with the same power supply. This is the most cost effective way of powering the LMP90xxx but is also the least ideal because noise from VIO can couple into VA and negatively affect performance. The second option involves powering VA and VIO with separate power supplies. These supply voltages can have the same amplitude or they can be different.

11.2 VREF

Operation with VREF below VA is also possible with slightly diminished performance. As VREF is reduced, the range of acceptable analog input voltages is also reduced. Reducing the value of VREF also reduces the size of the LSB. When the LSB size goes below the noise floor of the LMP90xxx, the noise will span an increasing number of codes and performance will degrade. For optimal performance, VREF should be the same as VA and sourced with a clean source that is bypassed with a ceramic capacitor value of 0.1 µF and a tantalum capacitor of 10 µF.

LMP90xxx also allows ratiometric connection for noise immunity reasons. A ratiometric connection is when the ADC’s VREFP and VREFN are used to excite the input device’s (i.e. a bridge sensor) voltage references. This type of connection severely attenuates any VREF ripple seen the ADC output, and is thus strongly recommended.