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

8 Protection Features

The circuit in Figure 2-1 has unique protection device U5, the TPS26614 which features both overvoltage and overcurrent protection with automatic retry. For current output mode, the device can switch off the current path in case the output node exceeded VSS or VCCI protecting the output stage from reverse current. For voltage output mode, TPS26614 can switch off if current exceeded 30mA protecting the U3 from overload or short circuit. The device can also switch off in case of voltage exceeding VCCI or VSS. To make sure proper protection for the voltage output stage, The recommendation is to keep VCC=VCCI.

The output transistor M2 gate is protected by Zener D2 to limit the Vgs(M2) voltage in case of output open circuit. In this case, U2 can pull down the Vg(M2) which can exceed the operating limits of gate voltage which is 20V for the chosen transistor. R12 can limit the current in D2 in case of such event. R13 is pulling up Vg(M2) making sure the M2 turns off in start-up.

TVS Diode D1 is protecting the output pin from Surge, EFT events, and limit the voltage of the output pin during these events. R14 protects the input of U4 by limiting the current. R1,R6, and R9 are doing the same protecting the inputs of U1 and U3 especially in the case if the input is applied on unpowered devices.