500 mA fixed 3.3 V LDO — PSRR and dropout drive the fit
The TPS73533DRVT is a single-output positive linear regulator from Texas Instruments, delivering a fixed 3.3 V at up to 500 mA. Power-supply rejection ratio (PSRR) is 66 dB at 100 Hz, rolling off to 22 dB at 100 kHz. Above 100 kHz the attenuation drops, so a post-LDO filter cap with low ESL is worth the board space.
65 µA quiescent — always-on and battery bias
Quiescent current is 65 µA typical, which sets the standby draw for an always-on regulator. In a battery-powered sensor node that sleeps at 10 µA system load, the LDO's own Iq dominates the sleep budget — a 65 µA overhead means the node's sleep current is 75 µA total, so the battery capacity calculation must include the regulator's draw, not just the load. The enable pin lets the system power down the regulator entirely, dropping Iq to near zero when the load is off. This is useful for gating a 3.3 V rail that only powers a transceiver during transmit windows.
Protection set and temperature grade
Integrated protection covers overcurrent, overtemperature, reverse polarity, and undervoltage lockout (UVLO). The UVLO threshold prevents the output from sourcing current when the input drops below the dropout headroom, avoiding brownout on downstream logic. The -40°C to 125°C operating range qualifies the part for industrial enclosures and under-hood automotive auxiliary rails (non-safety rated).