IR's High Current IR3847 Gen3 SupIRBuck® Delivers Superior Performance, Dramatically Reduces PCB size by 70% and Simplifies Design

Mar 19, 2013 | Technology Media

EL SEGUNDO, Calif. — International Rectifier, IR® (NYSE: IRF), a world leader in power management technology, today announced the introduction of the IR3847 high current Point-of-Load (POL) integrated voltage regulator that extends the current rating of IR's third generation SupIRBuck® family up to 25A in a compact 5x6 mm package.

As a result of a new thermally enhanced package using copper clip and several proprietary innovations in the controller, the IR3847 can operate at 25A without heatsink, and reduces PCB size by 20% compared to alternative integrated solutions and 70% compared to discrete solutions using a controller and power MOSFETs. A complete 25A power supply solution can be implemented in as little as 168mm2.

The new device integrates IR's latest generation power MOSFETs with a feature-rich, third generation SupIRBuck® controller that includes post-package precision dead-time trimming to optimize losses, and internal smart LDO to optimize efficiency across the entire load range. True differential remote sense essential for high current applications, 0.5% reference voltage accuracy in 25°C to 105°C temperature range, input feed-forward and ultra-low jitter combine to enable total output voltage accuracy less than 3% over line, load, and temperature, as required by high performance communications and computing systems.

As part of the new Gen3 SupIRBuck single input voltage (5V-21V) family, the IR3847 features a proprietary modulator scheme that reduces jitter by 90% compared to standard solutions. This has the dual benefit of reducing output voltage ripple by approximately 30% and allowing higher frequency/higher bandwidth operation for smaller size, better transient response and fewer output capacitors.

Available in a compact 5x6mm PQFN package, the IR3847 also offers market-leading electrical and thermal performance for 15A - 25A applications such as peak efficiency greater than 96% and temperature rise at 25A as low as 50°C. Other advanced features include external synchronization, sequencing, VTT tracking, and output voltage margining.

The pinout is optimized for easy placement of bypass capacitors and the internal thermally compensated current limit offers three settings that allow programmability without extra components and layout complications.

"With the new high current IR3847 with true differential remote sense, IR addresses the challenges of thermally- and space-constrained high density, high current applications by enabling a fully integrated solution up to 25A in only 168mm2 of PCB area delivering better than 3% total output accuracy right at the load. Competing devices are typically 5% or greater. By dramatically reducing jitter for pulse widths as small as 50ns, the IR3847 delivers higher closed loop bandwidth resulting in even better transient response and lower output capacitance while enabling higher frequency operation for even smaller size," said Cecilia Contenti, IR's POL Marketing Manager. "Our customers require benchmark performance and density without compromise. The IR3847 meets those needs and goes further by providing simplicity to facilitate the design process," said Ramesh Balasubramaniam, IR's POL Director of Marketing, Enterprise Power Business Unit.

The IR3847 offers the standard SupIRBuck features of switching frequency up to 1.5MHz, pre-biased start-up, input voltage aware enable, over voltage protection, power good, optional true output voltage sensing for open line feedback and adjustable OVP, internal soft-start and minimum input voltage of 1.0V (with ext. bias) and operating junction temperatures of -40oC to 125oC. Finally, it is qualified for the industrial market.

Part Number Package Circuit VIN Range (V) VOUT Range (V) IOUT(A) Switching Frequency
Single Output 1 - 21V 0.6 - 86%Vin 25 300 -1,500
Reference Design Featured Part VIN Range
VOUT Range
IOUT(A) Switching Frequency
IRDC3847 IR3847M 12 1.2 25 600

A datasheet and application notes are posted on the International Rectifier website at The IRDC3847 reference design featuring the new device is also available. A free user friendly, interactive, web-based design tool is available at to simplify design and calculate Bill of Materials, schematics, Bode diagram, simulation waveforms and thermal analysis for selected design inputs.

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