The XR75100 40-V synchronous step-down controller, developed by Exar, supports point-of-load (POL) supplies from industrial 24-V dc and 24-V ac rectified sources. Its emulated current-mode constant-on-time (COT) control scheme offers the fast transient response of conventional COT controllers, but doesn’t compromise other functionality. The device’s 0.008%/V line regulation across the entire input voltage range (5 to 40 V) and 1% output accuracy over the full temperature range boosts headroom to facilitate design implementations. Adjustable output voltage ranges from 0.6 to 30 V. The COT control loop enables operation with ceramic output capacitors, thus eliminating loop compensation and reducing component count. Supervisory and protection features ensure proper sequencing, safe operation under abnormal conditions, and light load operation. The XR75100, which comes in a 16-pin, 3- by 3-mm QFN package, will deliver core voltage rails for ASICs, FPGAs, DSPs, and other processors in medical, automotive, instrumentation, and other industrial applications.