This paper introduces the different types of current limiting/current foldback circuits used by Torex LDOs and how to use the VOUT vs. IOUT characteristics to predict the output voltage and output current variations at start-up.
The document introduces the concept of current‑foldback and current‑limiter circuits in low‑dropout (LDO) regulators, describing four circuit types (A‑D) and how they affect output voltage and current during start‑up. It also highlights the benefits of Torex LDOs with inrush‑current protection.
Detailed case studies of several Torex LDO models (e.g., XC6219B302MR, XC6221A302MR, XC6223F301) illustrate waveforms at start‑up, showing how the foldback circuit shapes inrush current and how different circuit types respond to over‑current conditions.
| Input voltage offset | 1.0 V above regulated output |
|---|---|
| Input capacitance used in examples | 1 pF |