The REF33xx features an advanced start-up circuit. Start-up time is almost independent of load (with a 0.1-μF to 10-μF load). Upon startup, the current boost circuit forces the output voltage. When the preset voltage is reached, the REF33xx switches to the second stage of output circuitry to precisely set the output voltage. Figure 18 shows the start-up time of the REF3325 for three different capacitive loads. In all three cases, the output voltage settles within 2 ms.