The TCR4DG18,LF is a 420 mA fixed-output LDO from Toshiba's TCR4DG series, delivering 1.8 V from a maximum 5.5 V input. Its 70 dB PSRR at 1 kHz means it attenuates switching-regulator ripple and digital noise on the input by a factor of ~3000 — critical when the 1.8 V rail feeds an ADC reference, PLL supply, or RF front-end where a few millivolts of feedthrough corrupt the signal. That 200 mV headroom budget is the design margin; a 2.5 V rail with ±5% tolerance dips to 2.375 V, leaving 102 mV of margin above the dropout ceiling.
420 mA continuous — the load ceiling and thermal envelope
Rated for 420 mA continuous output, the TCR4DG18,LF covers low-power SoC cores, sensor bias, and auxiliary logic rails. The 4-WCSPE package (0.65 x 0.65 mm) has a thermal resistance that depends on the PCB copper area — at 420 mA with 1.8 V output from a 3.3 V input, the power dissipation is 0.63 W, which the package can handle with adequate board-level heat spreading. Protection features include over-current, over-temperature, and short-circuit shutdown — the regulator survives a sustained output short without damage, and the thermal foldback prevents die temperature from exceeding the silicon limit during fault conditions.
Active lifecycle — no EOL risk for production BOMs
The Enable control feature lets the system designer gate the 1.8 V rail with a logic signal — useful for sequencing core and I/O supplies or shutting down the regulator in sleep modes to save quiescent current.
4-WCSPE footprint — board integration and rework
Housed in a 4-bump WCSPE (0.65 x 0.65 mm), the TCR4DG18,LF requires a PCB land pattern matching the Toshiba-recommended stencil aperture. The small pitch means solder paste volume and reflow profile matter — a 0.1 mm stencil thickness with a nitrogen atmosphere reduces voiding under the bumps. Rework requires a hot-air nozzle sized for the 0.65 mm body; the adjacent components must clear the nozzle footprint. Surface-mount assembly with standard lead-free reflow (260 °C peak) is compatible. The package is moisture-sensitive — bake before reflow if the floor life has been exceeded per the label MSL level.