ZHCSI09S June 2010 – August 2018 TPS65911
An inductor must be placed between the external FETs and the output capacitors. Together, the inductor and output capacitors form a double pole in the control loop that contributes to stability. In addition, the inductor is directly responsible for the output ripple, efficiency, and transient performance. As the inductance increases, the ripple current decreases, which typically results in an increase in efficiency. However, with an increase in inductance, the transient performance decreases. Finally, the selected inductor must be rated for the appropriate saturation current, core losses, and DC resistance (DCR).
The internal parameters for the converters are optimized for a 2.2-µH inductor, however using other inductor values is possible as long as they are carefully selected and thoroughly tested.
Use Equation 5 to calculate the recommended inductance for the converter.
After selecting the value of the inductor, use Equation 6 to calculate the peak current for the inductor in steady state operation, ILmax. The rated current of the inductor must be greater than the ILmax current.