7 Test Bench Validation

To validate the OPA593 and Darlington current booster DFC configuration, the OPA593 Evaluation Module (OPA593EVM) was modified to include the Darlington current booster output stage, replicating the circuit simulated in the Spice model shown in Figure 1-1. The circuit validations and improvements are summarized as follows:

1. The small-signal step transient response is stable with no overshoot or oscillation.
2. Both large-signal and small-signal step transient behaviors meet the design criteria.
3. The effective bandwidth of the current booster is measured at approximately 60kHz as specified.
4. Rise and fall times in signal step responses are within the specified design parameters.
5. Voltage accuracy requirements are met, and the circuit can source and sink current up to ±1A_dc.
6. The OPA593 and the current booster composite amplifier remain stable when driving a capacitive load up to 1µF.
7. Improvement: Enhanced heat dissipation for the Darlington booster transistors.
8. Improvement: Incorporation of short-circuit protection through programmable current-limiting features.
9. Improvement: Implementation of Enable/Disable control for shutdown and fault condition management.

The combination of the OPA593 and the current booster demonstrates that the small signal step transient is stable while driving 1µF capacitive load in parallel with a 52.5Ω resistive load. The small signal and larger signal step transient scope shots are captured and presented in Figure 7-1 and Figure 7-2.

In terms of current booster improvements, the specific application received less attention since the application note primarily focused on stability compensation for the composite amplifier using the OPA593 or similar op-amps. However, a few essential design considerations were noted. The OPA593 has built-in current limiting and enable/disable protection features. By leveraging these features, the thermal and fault protection circuits of the composite power amplifier can be simplified, providing adequate protection for the CBJT while reducing reliance on additional protective components.