SBOU024C august   2004  – july 2023 PGA309

 

  1.   1
  2.   Read This First
    1.     About This Manual
    2.     Related Documentation from Texas Instruments
    3.     If You Need Assistance
    4.     Information About Cautions and Warnings
    5.     FCC Warning
    6.     Trademarks
  3. 1Introduction
    1. 1.1  PGA309 Functional Description
    2. 1.2  Sensor Error Adjustment Range
    3. 1.3  Gain Scaling
    4. 1.4  Offset Adjustment
    5. 1.5  Voltage Reference
    6. 1.6  Sensor Excitation and Linearization
    7. 1.7  ADC for Temperature Sensing
    8. 1.8  External EEPROM and Temperature Coefficients
    9. 1.9  Fault Monitor
    10. 1.10 Over-Scale and Under-Scale Limits
    11. 1.11 Power-Up and Normal Operation
    12. 1.12 Digital Interface
    13. 1.13 Pin Configuration
  4. 2Detailed Description
    1. 2.1  Gain Scaling
      1. 2.1.1 PGA309 Transfer Function
      2. 2.1.2 Solving For Gain Settings
    2. 2.2  Offset Scaling
    3. 2.3  Zero DAC and Gain DAC Architecture
    4. 2.4  Output Amplifier
    5. 2.5  Reference Voltage
    6. 2.6  Linearization Function
      1. 2.6.1 System Definitions
      2. 2.6.2 Key Linearization Design Equations
        1. 2.6.2.1 Lin DAC Counts Conversion
      3. 2.6.3 Key Ideal Design Equations
        1. 2.6.3.1 Linearization Design
        2.       37
    7. 2.7  Temperature Measurement
      1. 2.7.1 Temp ADC Start-Convert Control
      2. 2.7.2 External Temperature Sensing with an Excitation Series Resistor
    8. 2.8  Fault Monitor
    9. 2.9  Over-Scale and Under-Scale
      1. 2.9.1 Over-Scale and Under-Scale Calculation
      2.      44
    10. 2.10 Noise and Coarse Offset Adjust
    11. 2.11 General AC Considerations
  5. 3Operating Modes
    1. 3.1 Power-On Sequence and Normal Stand-Alone Operation
    2. 3.2 EEPROM Content and Temperature Lookup Table Calculation
      1. 3.2.1 Temperature Lookup Table Calculation
        1. 3.2.1.1 Temperature Lookup Table Calculation
        2.       52
        3.       53
    3. 3.3 Checksum Error Event
    4. 3.4 Test Pin
    5. 3.5 Power-On Initial Register States
      1. 3.5.1 PGA309 Power-Up State
  6. 4Digital Interface
    1. 4.1  Description
    2. 4.2  Two-Wire Interface
      1. 4.2.1 Device Addressing
      2. 4.2.2 Two-Wire Access to PGA309
    3. 4.3  One-Wire Interface
    4. 4.4  One-Wire Interface Timeout
    5. 4.5  One-Wire Interface Timing Considerations
    6. 4.6  Two-Wire Access to External EEPROM
    7. 4.7  One-Wire Interface Initiated Two-Wire EEPROM Transactions
    8. 4.8  PGA309 Stand-Alone Mode and Two-Wire Transactions
    9. 4.9  PGA309 Two-Wire Bus Master Operation and Bus Sharing Considerations
    10. 4.10 One-Wire Operation with PRG Connected to VOUT
    11. 4.11 Four-Wire Modules and One-Wire Interface (PRG)
  7. 5Application Background
    1. 5.1 Bridge Sensors
    2. 5.2 System Scaling Options for Bridge Sensors
      1. 5.2.1 Absolute Scale
      2. 5.2.2 Ratiometric Scale
    3. 5.3 Trimming Real World Bridge Sensors for Linearity
    4. 5.4 PGA309 Calibration Procedure
  8. 6Register Descriptions
    1. 6.1 Internal Register Overview
    2. 6.2 Internal Register Map
      1. 6.2.1 Register 0: Temp ADC Output Register (Read Only, Address Pointer = 00000)
      2. 6.2.2 Register 1: Fine Offset Adjust (Zero DAC) Register (Read/Write, Address Pointer = 00001)
      3. 6.2.3 Register 2: Fine Gain Adjust (Gain DAC) Register (Read/Write, Address Pointer = 00010)
      4. 6.2.4 Register 3: Reference Control and Linearization Register (Read/Write, Address Pointer = 00011)
      5. 6.2.5 Register 4: PGA Coarse Offset Adjust and Gain Select/Output Amplifier Gain Select Register (Read/Write, Address Pointer = 00100)
      6. 6.2.6 Register 5: PGA Configuration and Over/Under-Scale Limit Register (Read/Write, Address Pointer = 00101)
      7. 6.2.7 Register 6: Temp ADC Control Register (Read/Write, Address Pointer = 00110)
      8. 6.2.8 Register 7: Output Enable Counter Control Register (Read/Write, Address Pointer = 00111)
      9. 6.2.9 Register 8: Alarm Status Register (Read Only, Address Pointer = 01000)
  9.   A External EEPROM Example
    1.     A.1 PGA309 External EEPROM Example
      1.      A.1.1 Gain and Offset Scaling for External EEPROM
      2.      94
  10.   B Detailed Block Diagram
    1.     B.1 Detailed Block Diagram
  11.   C Glossary
  12.   Revision History

C Glossary

    ADC

    Analog-to-digital converter
    BV

    Bridge nonlinearity with applied pressure.

    GUID-914B3C15-C730-460E-B3AE-41D0620FB934-low.gif
    BV MAX

    Maximum compensable nonlinearity
    BV –MAX
    GUID-F370D0BF-3526-4796-9DA1-A723422895E9-low.gif
    BV +MAX
    GUID-AA2401ED-3C80-4E1E-A8BA-FA682D5BC51F-low.gif
    CF

    External feedback capacitor connected between VSJ and VOUT, for stability.
    CMR

    Common-mode rejection
    DAC

    Digital-to-analog converter
    EMI

    Electromagnetic interference
    FSR

    Full-scale range of PGA309 output.

    GUID-4F1AE906-DD26-40E8-8FD1-6B846E717B61-low.gif
    FSS

    Full-scale bridge sensitivity for sensor at PMAX (for example, 2mV/V).
    GIDEAL

    Ideal gain

    GUID-2EAD2761-7D9E-4653-8CB0-4326193663DB-low.gif
    GL

    Gain of the PGA309 when using the Linearization circuit.

    GUID-018CD2B6-3285-48D6-9ABA-4916820DC36B-low.gif
    GNDA

    Analog ground
    GNDD

    Digital ground
    GT

    Total gain produced by the PGA309 of VOUT/VIN gain.

    GT = (Front-End PGA Gain)(Gain DAC)(Output Amplifier Gain)
    IVR

    Input voltage range of the PGA309.
    KLIN

    PGA linearization coefficient

    GUID-F3B8C23C-8FEE-4078-B36F-47B4B7CEEED4-low.gif
    KLIN –MAX

    Most negative linearization coefficient. Its value is determined by the selected range of bridge sensor nonlinearity compensation.
    KLIN +MAX

    Most positive linearization coefficient. Its value is determined by the selected range of bridge sensor nonlinearity compensation.
    KEXC

    PGA excitation coefficient. Scale factor on VREF.
    KP

    Pressure constant. Converts linear input pressure to nonlinear pressure detected by sensor; referenced to full-scale input pressure.
    LSB

    Least significant bit
    MSB

    Most significant bit
    P

    Pressure input
    PMIN

    Minimum sensor input pressure
    PMAX

    Maximum sensor input pressure
    PNL

    Nonlinear pressure output of bridge with linear pressure input P.
    POR

    Power-on reset function
    PRG

    Single-wire interface program pin
    RBRG

    Bridge resistor value
    RFB

    External feedback resistor connected to VFB.
    RFO

    Internal feedback resistor for the Output Amplifier.
    RFO EXT

    Additional external feedback resistor for the Output Amplifier.
    RGO

    Internal gain resistor for the Output Amplifier.
    RGO EXT

    Additional external gain resistor for the Output Amplifier.
    RISO

    External isolation resistor connected to VOUT.
    REFIN/REFOUT

    Voltage reference input/output pin
    RFI

    Radio frequency interference
    RTO

    Referred-to-output
    SCL

    Clock input/output for Two-Wire serial interface
    SDA

    Data input/output for Two-Wire serial interface
    TEMPIN

    External temperature signal input
    TEST

    Test/external controller mode pin
    VBRMAX

    Maximum bridge sensor output
    VCM

    Common-mode voltage applied to the PGA309 input.

    GUID-69C84C50-6810-4B4E-B02D-7324887867BE-low.gif
    VCOS

    Coarse offset voltage output of the coarse offset adjust DAC.
    VDIFF

    Differential voltage applied to the PGA309 inputs.

    VDIFF = VINP − VINN
    VEXC

    Bridge sensor excitation voltage

    GUID-321C0DD5-DECF-4930-8264-CBF06B010311-low.gif
    VEXC MAX

    Maximum bridge sensor excitation voltage

    GUID-09620751-2166-4DE7-A1F2-930FE1C55BC1-low.gif
    VEXC MIN

    Minimum bridge sensor excitation voltage

    GUID-3BA80ABC-2CF0-44BC-A70A-3823EF5FC157-low.gif
    VFB

    VOUT feedback pin
    VFRONT

    The output of difference amplifier A3, of the Front-End PGA309.
    VIN1

    Signal input voltage 1
    VIN2

    Signal input voltage 2
    VINN

    The positive input of internal auto-zero amplifier A1, of the Front-End PGA.
    VINP

    The positive input of internal auto-zero amplifier A2, of the Front-End PGA.
    VN

    Output voltage of one branch of the bridge.
    VOA1

    Output voltage of internal auto-zero amplifier A1.

    GUID-957BFDF8-498A-4B21-8DB4-CFD36FBCF79E-low.gif
    VOA2

    Output voltage of internal auto-zero amplifier A2.

    GUID-3837CF3A-2604-4C57-AD45-DD0DD55D0AA5-low.gif
    VOS

    Sensor offset voltage
    VOUT

    Analog output voltage of conditioned sensor
    VOUT ERR FSR

    Error in %FSR of VOUT
    VOUT FILT

    Filtered VOUT
    VOUT IDEAL

    Ideal output for a given pressure, P.

    GUID-2D11E938-44E8-4F8A-B18A-5238B4BBE150-low.gif
    VOUT MAX

    VOUT for maximum bridge sensor output
    VOUT MIN

    VOUT for minimum bridge sensor output
    VP

    Output voltage of one branch of the bridge.
    VREF

    Reference voltage used by the PGA309 (internal or external).
    VREFT

    Temperature VREF
    VS

    Supply voltage
    VSA

    Analog supply voltage
    VSD

    Digital supply voltage
    VSJ

    Output Amplifier summing junction
    VTEST

    Test signal
    VZERO DAC

    Output voltage of the Zero DAC