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

3 Buffered Reference

GUID-20231220-SS0I-ZDPT-PVC7-6LB3RTRGMDWJ-low.svg Figure 3-1 Buffered Reference

This topology uses one voltage reference IC and a single precision OP-AMP to drive multiple ADCs. This topology provides the best performance for all C2000 ADCs. It is especially recommended to use this topology for 16-bit differential ADCs, since there will be a considerable performance difference between unbuffered and buffered reference circuits. It is also recommended to use this topology when driving more than three ADCs.

Note: The zero-crossover technology of the OPA328 makes it possible to accurately drive the output voltage close to the supply voltage of the OP-AMP. For most traditional rail-to-rail OP-AMPs, this can cause an unacceptable input offset voltage. For details, see Reference-Buffer, ADC-Driver and Transimpedance Applications for OPAx328.

The 'B' options for OP-AMPs provide a cost-effective alternative to precision OP-AMPs, where DC performance is traded for cost. These amplifiers are able to drive the reference when the ADC is sampling at high frequencies, but there can be a DC error of up to 2mV due to the amplifiers' input offset error.