SBOS392H August   2007  – August 2019 REF3312 , REF3318 , REF3320 , REF3325 , REF3330 , REF3333

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      REF3312 in a Single-Supply Signal Chain
      2.      Dropout Voltage vs Load Current
  4. 4 Revision History
  5. 5 Device Comparison
  6. 6 Pin Configuration and Functions
    1. Table 1. Pin Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Typical Characteristics
  8. 8 Parameter Measurement Information
    1. 8.1 Thermal Hysteresis
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Start-Up Time
      2. 9.3.2 Low Temperature Drift
      3. 9.3.3 Power Dissipation
      4. 9.3.4 Noise Performance
    4. 9.4 Device Functional Modes
  10. 10Applications and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Applications
      1. 10.2.1 REF3312 in a Bipolar Signal-Chain Configuration
        1. 10.2.1.1 Design Requirements
        2. 10.2.1.2 Detailed Design Procedure
          1. 10.2.1.2.1 Op Amp Level-Shift Design
          2. 10.2.1.2.2 Differential Input Attenuator Design
          3. 10.2.1.2.3 Input Filtering
          4. 10.2.1.2.4 Component Selection
            1. 10.2.1.2.4.1 Voltage References
            2. 10.2.1.2.4.2 Op Amp
          5. 10.2.1.2.5 Input Attenuation and Level Shifting
          6. 10.2.1.2.6 Input Filtering
          7. 10.2.1.2.7 Passive Component Tolerances and Materials
        3. 10.2.1.3 Application Curves
          1. 10.2.1.3.1 DC Performance
          2. 10.2.1.3.2 AC Performance
  11. 11Power-Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Documentation Support
      1. 13.1.1 Related Documentation
    2. 13.2 Related Links
    3. 13.3 Receiving Notification of Documentation Updates
    4. 13.4 Community Resources
    5. 13.5 Trademarks
    6. 13.6 Electrostatic Discharge Caution
    7. 13.7 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

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

10.2.1.2 Detailed Design Procedure

Figure 19 depicts a simplified schematic for this design showing the MSP430 ADC inputs and full input conditioning circuitry. The ADC is configured for a bipolar measurement where final conversion result is the differential voltage, VDIFF, between the positive and negative ADC inputs, A1+ and A1–. The bipolar, ground-referenced input signal must be level-shifted and attenuated by the op amp so that the output is biased to VREF / 2 and has a differential voltage that is within the ±VREF / 2 input range of the ADC. The transfer function for the op-amp circuit simplifies to Equation 4.

Equation 4. REF3312 REF3318 REF3320 REF3325 REF3330 REF3333 q_a1_plus_sbos392.gif

where

  • R1 = R4
  • R5 = R2 || R3

The voltage applied to the negative ADC input, A1–, is based on the resistor divider formed by R6 and R7 and is set to VREF / 2 by setting R6 equal to R7, as shown in Equation 5.

Equation 5. REF3312 REF3318 REF3320 REF3325 REF3330 REF3333 q_a1_minus_sbos392.gif