7.3.2 Start-Up

The TPS795 uses a start-up circuit to quickly charge the noise reduction capacitor, C_NR, if present (see Functional Block Diagrams). This circuit allows for the combination of very low output noise and fast start-up times. The NR pin is high impedance so a low leakage C_NR capacitor must be used; most ceramic capacitors are appropriate for this configuration.

For the fastest start-up, apply V_IN first, and then drive the enable pin (EN) high. If EN is tied to IN, start-up is somewhat slower. To ensure that C_NR is fully charged during start-up, use a 0.1-µF or smaller capacitor.