Automotive-grade LDO for noise-sensitive rails
The TPS78428QDBVRQ1 is a fixed 2.8V output LDO from Texas Instruments, delivering 300mA continuous current in a SOT-23-5 package. The 115mV maximum dropout at 300mA full load means the input rail can dip to 2.915V before the output falls out of regulation — a tight headroom budget that matters when the LDO is fed from a pre-regulated 3.3V or 3.0V bus rather than a battery.
PSRR profile and noise rejection
PSRR starts at 60dB at 1kHz and rolls off to 30dB at 1MHz. This means the LDO effectively filters switching noise from a DC-DC converter upstream up to a few hundred kHz, but above ~300kHz the attenuation drops enough that a post-filter LC stage may be needed if the load is an analog sensor front-end or a precision ADC reference. The 30µA typical quiescent current (43µA max supply current) keeps the regulator's own draw low enough for always-on automotive modules that stay powered during key-off — the Iq is well below the 100µA threshold that would trigger a parasitic-load fault in most body-control ECUs.
Protection and control for harsh environments
Built-in over-current and over-temperature protection let the LDO survive a shorted output or a thermal runaway condition without external crowbar circuitry — the die simply folds back current and shuts down until the junction cools. The enable pin lets a supervisory circuit or a GPIO from the ECU hold the regulator off during startup sequencing, preventing the 2.8V rail from powering up before the 3.3V bus is stable.