A capacitor connected to this pin reduces the low frequency noise of the converter and sets the soft-start time. The larger the capacitor, the lower the noise and the longer the start-up time of the converter. The module has an internal 220-nF capacitor connected to the NR/SS pin. If no external capacitor is connected to the NR/SS pin, the default start-up time is 2.35 ms, although longer start-up times and additional noise reduction can be achieved with additional capacitance connected to the NR/SS pin. The maximum NR/SS cap is 3.3 µF for a start-up time of 35 ms.During soft start with a light load, the device skips switching pulses as needed to not discharge the output voltage. The device can start into a pre-biased output voltage.

The device achieves low noise by adding an R-C filter to the reference voltage, as shown in Functional Block Diagram. During start-up, the NR/SS capacitor is charged with a constant current of 75 µA (typical) to 0.8 V. Larger NR/SS capacitors provide for lower low frequency noise, as shown in Figure 6-29.