SNVS359E May 2005 – December 2014 LM5021
The LM5021 is designed to run from a power supply in the range of 7.25 V to 30 V connected to VIN. A capacitor is required from VIN to GND to supply startup energy for the converter. Typical values are a few µF to a few tens of µF. Electrolytic capacitors are acceptable here.
The internal circuits of the controller operate from an internal 8-V regulator that is brought out on VCC. The VCC pin needs a small bypass capacitor, typically 100-nF to 1-µF ceramic, closely coupled to the GND pin for best operation. It is not recommended to directly drive the VCC pin from another power source.
It is not recommended that the bias winding be connected to the VCC pin of the LM5021. Doing so can cause the device to operate incorrectly or not at all.