SBOA594 August   2024 OPA2990

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1 Introduction
  5. 2 Circuit Description
  6. 3 Supporting Multiple Output Ranges
  7. 4 Resistor Sizing, M2 Selection, and Other Design Considerations
  8. 5 Mode and Range Control
  9. 6 Supply Level for Current Output
  10. 7 Supply Levels for Voltage Output
  11. 8 Protection Features
  12. 9 Measurement Results
  13. 10Power Consumption
  14. 11Error Monte-Carlo Analysis
  15. 12Rise and Fall Times
  16. 13Building Multi-Channel Output
  17. 14Summary
  18. 15References

7 Supply Levels for Voltage Output

Voltage output stage has bipolar supply VCC, VSS. OPA2990S is rail to rail opamp, with output headroom only about 150-300mV from supply rails based on the output current. For bipolar output, make sure the supply is at least +0.5V from the maximum positive output, and -0.5V from the minimum output.

For the unipolar output case 0-5V and 0-10V, to make sure true-zero output a simple negative charge pump can be used to generate VSS. LM7705 is low noise, low cost charge pump that can generate -0.23V and is capable of sinking up to 26mA, making LM7705 a good choice for generating VSS in unipolar output case.

The minimum load in voltage mode, RLoad(min)=Vout(max)/Iout(max), assuming the voltage output is designed for 20mA output, then RLoad(min)=500Ω in case of ±10V output range.