The LM5021 is an off-line pulse width modulation (PWM) controller that contains all of the features needed to implement highly efficient off-line single-ended flyback and forward power converters using current-mode control. The LM5021 features include an ultra-low (25 µA) start-up current, which minimizes power losses in the high voltage start-up network. A skip cycle mode reduces power consumption with light loads for energy conserving applications (ENERGY STAR®, CECP, etc.). Additional features include under-voltage lock-out, cycle-by-cycle current limit, hiccup mode overload protection, slope compensation, soft-start and oscillator synchronization capability.
The LM5021 is a current‑mode PWM controller designed for power‑conversion applications. It offers selectable maximum duty‑cycle limits (80 % or 50 %), an under‑voltage lock‑out (UVLO), skip‑cycle mode, and programmable current‑limit circuitry. The device is supplied in MSOP‑8 and MDIP‑8 packages and includes pins for COMP, VIN, VCC, OUT, GND, CS, and RT/SYNC.
The datasheet provides detailed electrical characteristics, absolute maximum ratings, typical performance curves, and ordering information for the LM5021‑1, LM5021‑2, and related variants. Physical dimensions for both package types are listed, along with contact information for National Semiconductor support centers worldwide.
| Maximum duty‑cycle limit (LM5021‑1) | 80 % |
|---|---|
| Maximum duty‑cycle limit (LM5021‑2) | 50 % |
| Package types | MSOP‑8, MDIP‑8 |
The LM5021 is offered in MSOP‑8 and MDIP‑8 packages.
The LM5021‑1 version supports a maximum duty‑cycle of 80 %.