The feedback voltage at FB is compared to an internal 2.5-V reference. In normal operation (the output voltage is regulated), an on-time period is initiated when the voltage at FB falls below 2.5 V. The buck switch stays on for the programmed on-time, causing the FB voltage to rise above 2.5 V. After the on-time period, the buck switch stays off until the FB voltage again falls below 2.5 V. During start-up, the FB voltage is below 2.5 V at the end of each on-time, resulting in the minimum off-time. Bias current at the FB pin is less than 5 nA over temperature.