SPRABY5 January   2024 TMS320F2800132 , TMS320F2800133 , TMS320F2800135 , TMS320F2800137 , TMS320F2800152-Q1 , TMS320F2800153-Q1 , TMS320F2800154-Q1 , TMS320F2800155 , TMS320F2800155-Q1 , TMS320F2800156-Q1 , TMS320F2800157 , TMS320F2800157-Q1 , TMS320F280021 , TMS320F280021-Q1 , TMS320F280023 , TMS320F280023-Q1 , TMS320F280023C , TMS320F280025 , TMS320F280025-Q1 , TMS320F280025C , TMS320F280025C-Q1 , TMS320F280033 , TMS320F280034 , TMS320F280034-Q1 , TMS320F280036-Q1 , TMS320F280036C-Q1 , TMS320F280037 , TMS320F280037-Q1 , TMS320F280037C , TMS320F280037C-Q1 , TMS320F280038-Q1 , TMS320F280038C-Q1 , TMS320F280039 , TMS320F280039-Q1 , TMS320F280039C , TMS320F280039C-Q1 , TMS320F280040-Q1 , TMS320F280040C-Q1 , TMS320F280041 , TMS320F280041-Q1 , TMS320F280041C , TMS320F280041C-Q1 , TMS320F280045 , TMS320F280048-Q1 , TMS320F280048C-Q1 , TMS320F280049 , TMS320F280049-Q1 , TMS320F280049C , TMS320F280049C-Q1 , TMS320F28075 , TMS320F28075-Q1 , TMS320F28076 , TMS320F28374D , TMS320F28374S , TMS320F28375D , TMS320F28375S , TMS320F28375S-Q1 , TMS320F28376D , TMS320F28376S , TMS320F28377D , TMS320F28377D-EP , TMS320F28377D-Q1 , TMS320F28377S , TMS320F28377S-Q1 , TMS320F28378D , TMS320F28378S , TMS320F28379D , TMS320F28379D-Q1 , TMS320F28379S

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 Symptoms of an Unreliable Reference
    2. 1.2 ADC Principle of Operation
    3. 1.3 Layout Guidelines
    4. 1.4 Key Reference Buffer Specifications
    5. 1.5 VREFHI Example for C2000 MCUs
  5. 2Unbuffered Reference
  6. 3Buffered Reference
  7. 4VDDA as Reference Voltage for ADC
  8. 5Summary
  9. 6References
  10. 7ADC Related Collateral

1.5 VREFHI Example for C2000 MCUs

To illustrate the importance of ADC reference accuracy, this section presents a basic scenario in which the ADC reference has a DC error. If VREFLO= 0 V and VREFHI = 2.5V, then each of the 4096 possible codes of a 12-bit ADC represents a voltage of about .61mV.

If VREFHI is not at the expected voltage, the value of each ADC code is no longer .61mV. In an extreme case, if the ADC reference voltage unexpectedly drops to 2.4V, then each code represents a voltage range of about .59mV. If the ADC returns the code 4090, it appears to the user that the sampled voltage is almost 2.5V. The real input voltage is almost 100mV lower!