LM3543 Triple Port USB Power Distribution Switch and Over-Current Protection
The LM3543 provides three independent high‑side power switches for USB hubs and other USB‑powered devices. Each port can deliver up to 500 mA continuous current, with a typical on‑state resistance of 90 mΩ, ensuring compliance with USB voltage‑drop requirements.
Key features include active‑high or active‑low enable inputs, fault‑flag outputs for over‑current, undervoltage lockout and thermal shutdown, and a current‑foldback mechanism that reduces power consumption during overload conditions. The device is supplied in a 16‑pin SOIC package and operates from 2.7 V to 5.5 V input across an ambient temperature range of –40 °C to 85 °C.
| Input Voltage Range | 2.7 V to 5.5 V |
|---|---|
| Continuous Output Current per Port | 500 mA |
| On‑state Resistance (typ.) | 90 mΩ |
| Maximum Standby Supply Current | 5 pA |
| Ambient Temperature Range | -40 °C to 85 °C |
| Package Type | 16‑Pin SOIC |
The LM3543 switches have a typical on‑state resistance of about 90 mΩ when the input voltage is 5 V.
It uses a current‑limit circuit with a typical threshold of 2 A; when exceeded, the switch folds back to a 1 A limit and asserts a fault flag.
The device is available in active‑high (LM3543‑H) and active‑low (LM3543‑L) enable versions, both TTL and CMOS compatible.