I need a boost converter: 4~5 Volt in, 14 Volts out @ 100 mA for a battery powered application. Webench suggested an LM2735X based circuit with an unshielded inductor and 45 degree phase margin. I selected a very similar but slightly larger shielded inductor. The phase margin went to 15 degrees. I changed back to the original inductor and the phase margin went to 14 degrees!
The Bode plots seemed to be nonsense. The original had only -20 dB of gain at 1 Hz. with the shielded inductor. With the new inductor the phase is between -100 and -200 degrees out to 100 kHz, then dived to -360 degrees and suddenly spiked to about 0 degrees at 900 kHz.
Is the simulation working correctly? If so, how can I change to a shielded inductor and maintain an acceptable phase margin?