What this supervisor monitors and why the threshold matters
The TPS3840PL43DBVR is a single-channel power supply monitor from Texas Instruments that asserts a reset signal when the monitored voltage drops below 4.3V. That 4.3V threshold is a standard choice for 5V rails — it catches a brownout before the downstream logic loses its state, but stays high enough to avoid nuisance resets during normal ripple. The reset output is active low and push-pull, meaning it drives the reset line directly without an external pull-up resistor. That saves one resistor per rail on the BOM and keeps the trace count low in tight layouts.
Timeout, temperature range, and package fit
The reset timeout is 619ms typical — long enough to let the supply stabilise after a glitch, short enough that the system boots without a noticeable delay. The part comes in an SC-74A / SOT-753 package, also listed as SOT-23-5 supplier device package. The 5-pin footprint is compact and widely used — the 0.95 mm pitch and 2.9 mm body length fit on a two-layer board without fan-out issues.
There is no announced PCN or EOL, so it can be designed into a long-run BOM without an immediate second-source contingency. The base product number is TPS3840, and the suffix encodes the threshold voltage and output type — the PL43 indicates the 4.3V threshold and push-pull output. ROHS3 compliant, surface-mount on tape and reel or cut tape.