7.4.1 Prebias Start-Up Capability

At start-up, the LMZ10503EXT is in a prebiased state when the output voltage is greater than zero. This often occurs in many multi-rail applications such as when powering an ASIC, FPGA, or DSP. The output can be prebiased in these applications through parasitic conduction paths from one supply rail to another. Even though the LMZ10503EXT is a synchronous converter, it will not pull the output low when a prebias condition exists. The LMZ10503EXT will not sink current during start-up until the soft-start voltage exceeds the voltage on the FB pin. Because the device does not sink current it protects the load from damage that might otherwise occur if current is conducted through the parasitic paths of the load.