Fixed 9V rail from a 16V input bus
The BA90BC0FP-E2: The BA90BC0FP- is a single-output positive linear regulator from ROHM Semiconductor, delivering a fixed 9V output at up to 1A continuous. The 16V maximum input gives about 7V of headroom at the nominal rail — enough to ride through a lightly regulated 12V bus without the dropout margin getting tight. Packaged in the TO-252-3 (DPak) footprint, it mounts on a standard surface-mount pad with the exposed tab carrying the ground return and thermal path.
What the 0.5 mA quiescent current means for always-on rails
The 0.5 mA quiescent current (Iq) is the regulator's own draw when delivering the rated output. For a 9V rail that powers a microcontroller in standby, this Iq is roughly half the budget of older bipolar regulators — the BA90BC0FP- uses a CMOS output stage to keep the ground pin current low enough that the thermal contribution from the bias is negligible at light load. At full 1A output the maximum supply current is 900 µA, so the efficiency loss from the bias stays under 0.1% even at the heavy end. The trade-off is that the dropout voltage is higher than a low-Vin LDO — the fixed 9V output needs the input to stay above roughly 10.5V to regulate cleanly, which the 16V max input comfortably accommodates.
Over-current and over-temperature — built-in, not external
The protection block includes over-current limiting and thermal shutdown, both integrated on-die. The current limit folds back the output before the pass element enters secondary breakdown; the thermal shutdown trips at a junction temperature around 150°C (typical for ROHM's process) and auto-recovers after the die cools. No external current-sense resistor or thermal watchdog is needed. For the PCB layout engineer: the TO-252 tab is the main heat path. The datasheet's thermal resistance assumes a minimum copper area on the drain pad — a 1-inch-square pour on a 2-layer board drops RθJA by roughly 40% compared to a minimal pad.
Active production — current lifecycle and compliance
No pin-compatible second-source or official successor is listed — the part is a single-source item in ROHM's portfolio.