The ST1S40 and ST1S41 are synchronous switching voltage regulators with integrated MOSFETs, built-in ST 20 V BCD6 technology with 3 A and 4 A maximum DC current capability, able to withstand an operating input voltage up to 18 V. These devices can be considered a “value line” in the ST portfolio, meaning that target applications are those where cost saving is paramount. The efficiency, robustness, high output current capability, and ease of use allow customers to achieve cost reduction without compromising performance. The ST1S40/41 are 850 kHz fixed-frequency PWM synchronous step-down regulators with internal compensation. They can operate from 4 V to 18 V input, and they can regulate an output voltage as low as 0.8 V. With the ability to operate at 100% duty cycle, the output voltage can be adjusted almost up to Vin, which means ST1S40/41 are able to follow the input voltage with the lowest possible dropout voltage. The ST1S40/41 integrated 95 mΩ high side switch and 69 mΩ synchronous rectifier (low side switch) allow a high efficient power conversion. The peak current mode control with internal compensation delivers a very compact solution with minimal components count. Internal soft-start (to reduce inrush current at start up), cycle by cycle current limit, and short circuit protection with foldback make the ST1S40 practically indestructible. Stability is guaranteed with low ESR ceramic caps, which contributes in reducing the overall cost of the solution. ST1S40/41 are available in VFQFPN 4 mm x 4 mm 8-lead package, HSOP-8 (SO8 with exposed pad) and thermally enhanced SO-8 (see the table on the slide for order codes). The DFN and HSOP versions of ST1S40 have the same pin-out as the best-selling ST1S10 from ST, except for the synchronization pin which is not available in ST1S40. A typical application schematic is shown on the slide. Very few external components are needed for operation: the R1/R2 resistor divider to set the output voltage, input and output capacitors, and the inductor (a small 3.3 µH, due to the high switching frequency). The ST1S40 is easy to use and can fit in applications where board space saving is important.