78 dB at 120 Hz — the ripple-rejection number that matters for a 5 V rail
The BA17805CP-E2: The BA17805CP-: The ROHM BA17805CP- is a fixed 5 V output, 1 A positive linear regulator in the TO-220CP-3 package. Its 78 dB power-supply rejection ratio at 120 Hz is the headline spec: that is the frequency of full-wave-rectified mains ripple, so this part is tuned for industrial and appliance designs where the unregulated DC bus comes from a 50/60 Hz transformer, bridge rectifier, and bulk capacitor. The 25 V input maximum gives comfortable headroom for a 24 V nominal rail, and the 2 V dropout at 1 A means you need at least 7 V on the input to hold regulation at full load — standard for a 78xx-series part, not a low-dropout regulator.
1 A output — sizing the load budget and the heatsink
At 1 A output with a 24 V input dropping to 5 V, the regulator dissipates 19 W. The TO-220CP-3 package can handle that only with an adequate heatsink — the thermal pad on the tab is the primary heat path. For continuous loads above 500 mA, factor in a heatsink with forced airflow or a larger fin area. The 4.5 mA quiescent current and 6 mA supply maximum are typical for a bipolar 78xx-family part; they add negligible power loss compared to the dropout dissipation.
Industrial temperature range — not just a commercial part
The TO-220CP-3 package with cropped leads still fits standard TO-220 heatsink clips and PCB footprints, but the shorter leads reduce the standoff height — verify clearance to the next board or enclosure wall if you are retrofitting into an existing mechanical design.
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