Vicor Full-chip PRM-RS Customer Board - Manual (Page 16)

UG:009 vicorpower.com Applications Engineering: 800 927.9474 Page 16
10.0 Advanced Modifications
10.1 Stability, Bandwidth and Transient Response
The nominal compensation of the full-chip PRM-RS Customer Board is set to provide relatively low
bandwidth in order to ensure stability under all of the recommended configurations. The closed
loop frequency response varies as a function of line, load, trim, and output capacitance. Refer to
the PRM ® module data sheet for a detailed description and AC model. Adding additional
capacitance to the output of the PRM or VTM ® Customer Board may result in instability. When
testing transient response, it is important for the user to understand that response is a function of
compensation which should be optimized based on the end requirements for best performance. An
example transient response waveform, taken with a passive resistive load, is shown below. As
illustrated, the recovery time is on the order of 180 µsec. It should be noted that with control loop
optimization, faster transient response recovery times are possible.
10.1.1 Compensation Adjustment
The sense and compensation circuit is shown below. Refer to the BOM (4.3) for component
values. If higher bandwidth, faster transient response, and/or operation outside of the
recommended configurations are desired, the user may adjust the compensation, referring to
the appropriate PRM module data sheet for guidelines. This type of tuning is highly recommended
and generally requires the use of a network analyzer to measure the closed loop response.
Stability must be verified across all line, load, and trim conditions. Typically maximum crossover
frequency will occur at full load, and minimum crossover frequency will occur at minimum load.
Examples of closed loop response plots are illustrated below.
Figure 13: Example PRD48BF480T400A00
transient response,
Remote Sense Configuration