ZHCSCA8A March 2014 – April 2019 TPS65286
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 very large and would require large amounts of current to quickly charge the capacitor to the output voltage level. The large currents necessary to charge the capacitor may make the TPS65286 reach the current limit or 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 21. The soft-start circuit requires 1 nF per around 0.109 ms to be connected at the SS terminal. For the example circuit, the output capacitor value is 47 nF and the soft-start time is 5.1 ms. In TPS65286, Iss is 5.5 µA and Vref is 0.6 V.