STDA041 October   2026 OPA690

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 Design Summary
  5. 2Theory of Operation
    1. 2.1 Circuit Overview
    2. 2.2 Closed-loop Operation
    3. 2.3 FET Operation Region
  6. 3Design Procedure
    1. 3.1 Choosing FET
      1. 3.1.1 Ciss
      2. 3.1.2 Compliance Voltage Range
      3. 3.1.3 Safe Operating Area (SOA)
    2. 3.2 Rsense Selection
      1. 3.2.1 Effect of ESL
    3. 3.3 Opamp Selection
      1. 3.3.1 Bandwidth
      2. 3.3.2 Slew Rate
      3. 3.3.3 Opamp Output Current
  7. 4Design Based Component Selection
    1. 4.1 Design for Trise = 100ns
      1. 4.1.1 FET Selection
      2. 4.1.2 Rsense Selection
      3. 4.1.3 Opamp Selection
        1. 4.1.3.1 Bandwidth
        2. 4.1.3.2 Slew Rate
        3. 4.1.3.3 Output Current
    2. 4.2 Architecture Selection (Quick Reference)
  8. 5Circuit Architecture Selection
    1. 5.1 Single Feedback Method
    2. 5.2 Dual Feedback Method
    3. 5.3 Enhanced Dual Feedback Method
  9. 6Results
  10. 7Related Documentation

Abstract

As data-center computing demands higher-performance power management, the need for precise transient response testing becomes critical. This technical white paper presents a high-speed, high-current voltage-controlled current source (VCCS) optimized for applications such as electronic load, laser drivers. The design focuses on achieving a rapid rise-time (100ns) and high output current (up to 150A pulsed) while maintaining stability and voltage compliance. The paper details a comprehensive design procedure, covering critical component selection for power MOSFETs (focusing on saturation region operation, input capacitance, and safe operating area), sense resistor optimization to balance power dissipation and ESL-induced rise-time constraints, and opamp selection based on bandwidth, slew rate, and output current requirements. Additionally, the document evaluates various circuit architectures, including the use of damping resistor (Rdamp) and dual-feedback topologies to suppress parasitic oscillations and optimize settling time for modern GPU and CPU power supply applications.