Choose compensation components for a stable control loop using the procedure outlined as follows.
- Based on a specified loop gain crossover
frequency, fC, of 50kHz, use Equation 38 to calculate RCOMP, assuming an effective output capacitance of 80μF (2 ×
47µF TDK CGA6P1X7S1A476M250AC capacitors). Choose a standard value for RCOMP of
8.66kΩ.
Equation 38.
- To provide adequate phase boost at crossover
while also allowing a fast settling time during a load or line transient, select
CCOMP to place a zero at the higher of (1) one eighth of the crossover
frequency, or (2) the load pole. Choose a standard value for CCOMP of 2.2nF.
Equation 39.
Such a low capacitance value also helps
to avoid output voltage overshoot when recovering from dropout (when the input voltage
is less than the output voltage set point and VCOMP is railed high).
Note: Set a fast loop with high RCOMP and low CCOMP values to improve the response when recovering from operation in dropout.