The VRTS 1.5 voltage regulator demo board from PICOTEST can be used to demonstrate how a network analyzer can be used to determine the stability of a voltage control loop without interfering with the electronic circuit.
A system to be supplied can be disturbed by unexpected oscillations in the voltage control loop when the load changes. Critical resonance ranges can be determined by measuring the phase response in the feedback path. The phase reserve provides information about the stability of a control loop; it is determined in the associated Bode diagram. If the feedback path can be reached, the complete Bode diagram of the control loop can be measured with the aid of a network analyzer. In some cases the feedback path is internally wired and therefore cannot be contacted. With the so-called NISM method (Non-Invasive Stability Measurement), the phase reserve of the voltage regulator can be determined from an output impedance measurement.
The VRTS 1.5 demoboard is a discrete BJT voltage regulator (Bipolar Junction Transistor) with an input voltage of 7 to 10 V and an output voltage of 3.3V. In connection with the corresponding PICOTEST signal injector test adapters J21XXA, the demoboard supports the simulation of the following measurement functions:
- Power Supply Rejection Ratio (PSRR = ratio of the noise suppression of the supply voltage; with test adapter J2120A or J2111A)
- Measurement of the phase response in the feedback path (with test adapter J2111A)
- Measurement of a BODE diagram (with test adapter J2100A)
- Non-invasive stability measurement (NISM, with test adapter J2111A)
- Load steps (with test adapter J2111A)
- Noise density (with test adapter J2130A or P2130A)