JAJS472C August 2010 – April 2018 TPS54320
PRODUCTION DATA.
The slow-start capacitor determines the minimum amount of time it takes for the output voltage to reach its nominal programmed value during power up. This is useful if a load requires a controlled voltage slew rate. This is also used if the output capacitance is large and requires a large amount of current to charge the capacitor to the output voltage level. The large currents necessary to charge the capacitor may either make the TPS54320 reach the current limit or the excessive current draw from the input power supply may cause the input voltage rail to sag. Limiting the output voltage slew rate solves both of these problems. The soft-start capacitor value can be calculated using Equation 29. The example circuit has the soft-start time set to an arbitrary value of 3.5 ms, which requires a 10-nF capacitor. In the TPS54320, Iss is 2.3 µA and Vref is 0.8 V.