SBVS311A November 2019 – March 2020 TPS7A54
The load-step transient response is the output voltage response by the LDO to a step in load current, whereby output voltage regulation is maintained. There are two key transitions during a load transient response: the transition from a light to a heavy load, and the transition from a heavy to a light load. The regions shown in Figure 46 are broken down in this section. Regions A, E, and H are where the output voltage is in steady-state regulation.
During transitions from a light load to a heavy load:
During transitions from a heavy load to a light load:
Transitions between current levels changes the internal power dissipation because the TPS7A54 is a high-current device (region D). The change in power dissipation changes the die temperature during these transitions, and leads to a slightly different voltage level. This different output voltage level shows up in the various load transient responses.
A larger output capacitance reduces the peaks during a load transient but slows down the response time of the device. A larger dc load also reduces the peaks because the amplitude of the transition is lowered and a higher current discharge path is provided for the output capacitor.