SBVS311A November 2019 – March 2020 TPS7A54
At 4.0 A and 0.9 VOUT, the dropout of the TPS7A54 has a 240-mV maximum dropout over temperature; thus, a 300-mV headroom is sufficient for operation over both input and output voltage accuracy. At full load and high temperature on some devices, the TPS7A54 can enter dropout if both the input and output supply are beyond the edges of the respective accuracy specification.
For a 0.9-V output. use external adjustable resistors. See the resistor values in listed Table 5 for choosing resistors for a 0.9 V output.
Input and output capacitors are selected in accordance with the Recommended Capacitor Types section. Ceramic capacitances of 47 µF for the input and one 47-µF capacitor in parallel with two 10-µF capacitors for the output are selected.
To satisfy the required start-up time and still maintain low noise performance, a 100-nF CNR/SS is selected. Equation 9 calculates this value.
At the 4.0-A maximum load, the internal power dissipation is 1.2 W and corresponds to a 52°C junction temperature rise for the RPS package on a standard JEDEC board. With a 55°C maximum ambient temperature, the junction temperature is at 107.0°C. To further minimize noise, a feed-forward capacitance (CFF) of 10 nF is selected.