SBOS392I August   2007  – April 2026

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison
  6. 5 Pin Configuration and Functions
  7. 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 Typical Characteristics
  8. 7 Parameter Measurement Information
    1. 7.1 Thermal Hysteresis
  9. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Start-Up Time
      2. 8.3.2 Low Temperature Drift
      3. 8.3.3 Power Dissipation
      4. 8.3.4 Noise Performance
    4. 8.4 Device Functional Modes
  10. 9 Applications and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 REF3312 in a Bipolar Signal-Chain Configuration
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
          1. 9.2.1.2.1 Op Amp Level-Shift Design
          2. 9.2.1.2.2 Differential Input Attenuator Design
          3. 9.2.1.2.3 Input Filtering
          4. 9.2.1.2.4 Component Selection
            1. 9.2.1.2.4.1 Voltage References
            2. 9.2.1.2.4.2 Op Amp
          5. 9.2.1.2.5 Input Attenuation and Level Shifting
          6. 9.2.1.2.6 Input Filtering
          7. 9.2.1.2.7 Passive Component Tolerances and Materials
        3. 9.2.1.3 Application Curves
          1. 9.2.1.3.1 DC Performance
          2. 9.2.1.3.2 AC Performance
    3. 9.3 Power-Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Example
  11. 10Device and Documentation Support
    1. 10.1 Documentation Support
      1. 10.1.1 Related Documentation
    2. 10.2 Receiving Notification of Documentation Updates
    3. 10.3 Support Resources
    4. 10.4 Trademarks
    5. 10.5 Electrostatic Discharge Caution
    6. 10.6 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

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9.2.1.2.4.1 Voltage References

The REF33xx series of precision low-power voltage references pair well with the low power consumption of the MSP430, while achieving the target accuracy goals. The 16-bit converter in the MSP430F2013 accepts an external reference voltage from 1V to 1.5V with a typical reference input of 1.25V, as shown in Table 9-1.

Table 9-1 SD16_A, External Reference Input (MSP430F20x3)
PARAMETER(1) TEST CONDITIONS MIN TYP MAX UNIT
VREF(I) Input voltage range VCC = 3V, SD16REFON = 0 1 1.25 1.5 V
IREF(I) Input current VCC = 3V, SD16REFON = 0 50 nA
(1) Over recommended ranges of supply voltage and operating free-air temperature (unless otherwise noted).

The REF3312 provides the desired 1.25V reference voltage for the MSP430 ADC. The accuracy of the REF3312 output, shown in the Electrical Characteristics, directly affects the accuracy of the entire system and must be less than the desired unadjusted error goals. The REF3312 maximum ±0.15% initial accuracy specification is equal to the unadjusted error design goal of 0.15%, indicating that most of the error budget in this design must be devoted to the reference accuracy.

The 3.3V system supply voltage that powers the MSP430 can also supply other devices, and therefore can have regulation and noise issues. The REF3330 creates an accurate and stable 3.0V output used by the op amp, REF3312, and other low-power analog circuitry. The REF33xx series has a drop-output voltage of VOUT + 200mV; therefore, as long as the input supply remains above 3.2V, the REF3330 produces a regulated 3.0V output. The output current for the REF33xx series is specified at ±5mA, as shown in Figure 6-9, and is sufficient for the REF3312 and a low-power op amp.