JAJSGV5 January 2019 TPS54540B
PRODUCTION DATA.
To ensure proper operation of the device and to keep the output voltage in regulation, the input voltage at the device must be above the value calculated with Equation 43. Using the typical values for the RHS, RDC and VF in this application example, the minimum input voltage is 5.56 V. The BOOT-SW = 3 V curve in Figure 1 was used for RDS(on) = 0.12 Ω because the device operates with low dropout. When operating with low dropout, the BOOT-SW voltage is regulated at a lower voltage because the BOOT-SW capacitor is not refreshed every switching cycle. In the final application, the values of RDS(on), Rdc, and VF used in Equation 43 must include tolerance of the component specifications and the variation of these specifications at their maximum operating temperature in the application. In this application example, the calculated minimum input voltage is near the input voltage UVLO for the TPS54540B so the device may turn off before going into dropout.