Innovative isolated and non-isolated SMT DC/DC converters

Over many years, high-efficiency switching converter replacements for the traditional ‘78xx series’ linear regulators have been released. Although ‘drop-in’ through-hole equivalent parts have been popular, surface-mount types are now preferred.

As one of the first manufacturers to make a switching regulator module, RECOM first addressed the market with an encapsulated ‘gull-wing’ 1A-rated part, the R-78AA-1.0 series, which has a wide input range of up to 18V, allowing 5V, 9V, 12V or 15V unregulated supplies to be used, and fixed regulated outputs of 1.5V,1.8V, 2.5V or 3.3V, in a volume of just 1.75cm³. For applications where a low-profile open-frame product was preferred, the RECOM ROF-78E series offered 0.5A rating with a wider input range of up to 36V and fixed output voltages of 3.3V, 5V or 12V in a total volume of 0.68cm³.

The RECOM RPH-3.0 is a complete 3A power module in a compact 10 x 12 x 4mm QFN SMD package. Despite its small size, it is a complete power module, requiring only input and output MLCC capacitors and two output voltage setting resistors to create a fully functioning power supply. Unusually for an on-board SMD power supply module, it has a very wide input voltage range from 4.5V to 55 V DC, allowing either 48V batteries or 5V, 12V, 24V or 48V power supply rails to be used. The output voltage can be set anywhere in the range of 1V-15V, allowing, for example, 3.3V, 5V or 12V output voltages all with a single part. The RPH-3.0 features on/off control, a power good signal, programmable soft-start, selectable switching frequency and full protection against short circuits, over-voltage, over-temperature and overload. With derating, the part can operate reliably at ambient temperatures of up to 125°C.

The RPL series comprises 1A-20A compact power modules, including the RPL-1.0, RPL-3.0, and RPL-5.0 series, housed in a tiny 3 x 3mm LGA packages. Despite their small footprint, these modules are fully self-contained power solutions, necessitating only input and output MLCC capacitors, along with two output voltage setting resistors, to build a fully operational power supply. For the 3A and 5A variants, a sense input compensates for potential I²R losses in the output tracks. Moreover, all versions feature enable and power good connections, facilitating straightforward power rail sequencing in distributed power architecture setups. An internal LDO regulator furnishes a fixed 3.3 VDC/20mA output, suitable for pull-ups or external control logic.

The wide input voltage range caters to standard 3.3, 5, 12, or 15 VDC supply rails. During shutdown, the modules have a minimal power consumption, drawing only 15µA (2µA for the RPL-5.0), making them ideal for battery-powered portable applications, where they can be used as a combined regulator and power switch.

The RPL-10 and RPL-20 offer industry-leading high current capabilities in a compact SMD 7 x 7mm package. Like their other RPL counterparts, these modules are self-sufficient power solutions, necessitating only a few passive resistors and capacitors for full functionality. They also feature enable, tracking, and power good connections, enabling seamless power rail sequencing in distributed power architecture scenarios, along with adjustable operating frequency and start-up times.

All of the RPL series employ constant on-time (COT) current control, coupled with a separate slower control loop for output stability, meaning that the internal controller swiftly reacts to abrupt load transients while ensuring precise load regulation, without sacrificing transient response. This characteristic renders the RPL series ideal for powering dynamic loads such as microcontrollers, radios, or pulsed current imaging systems.

The RPZ-0.5 and RPZ-1.0 versions in 2mm x 2mm QFN packages accept an input voltage range from 2.3V up to 5.5V, allowing 3.3V or 5V fixed supply voltages or a single Li-ion cell to be used. The 0.5A or 1A output voltage can be set with two resistors in the range from 0.6VDC up to 5.25VDC. The RPZ-2.0 and RPZ-3.0 versions in 2.5mm x 3.5mm QFN packages accept an input voltage range from 2.75V up to 6V, allowing 3.3V or 5V fixed supply voltages or a single Li-ion cell to be used. The 2A or 3A output voltage can be set with two resistors in the range from 0.6VDC up to 5.5VDC. The RPZ-6.0 version in a 4 x 6mm QFN package accepts an input voltage range up to 7VDC and down to 2.75VDC, allowing 3.3V or 5V fixed supply voltages or a single Li-ion cell or a 6V battery to be used. The 6A output voltage can be set with two resistors in the range from 0.6VDC up to 6.65VDC.

The RPZ series internal controller uses constant on-time control for a fast reaction to abrupt load transients combined with a separate slow control loop for output stability, offering precise load regulation without compromising on transient response. This makes them especially suitable for powering dynamic loads such as microcontrollers, radios or pulsed current imaging systems.