Micro DC/DC converter integrates coil for EMI-sensitive wearables

November 18, 2014 // By Julien Happich
At electronica, Torex Semiconductor has announced what the company claims to be the world's smallest 1A micro DC/DC converter, namely the XCL219/XCL220 series.

Measuring only 2.5x2.0x1.0mm, this new family of step-down micro DC/DC converters has been designed to minimize EMI emissions for sensitive RF applications. It also maximizes efficiency while delivering a very stable output with low peak to peak ripple Voltage (<10mV).

The devices rely on HiSAT-COT, Torex’s Constant ON Time architecture to provide extremely fast load transient response performance in comparison to standard DC/DC solutions. HiSAT-COT also provides less fluctuation in oscillation frequency against load and input voltage when compared to traditional COT control architectures. Operating from input voltages as low as 2.5V up to 5.5V and consuming only 25uA when operating with no load, the XCL219/XCL220 is an excellent fit for applications where PCB space is at a premium. Internally, the XCL utilizes a simple package construction with low production costs for a truly cost effective solution in high volume consumer applications.

According to manufacturer Torex, when tested and compared with a conventional DC/DC circuit with an external coil, the XCL219/XCL220 series and their integrated coil show a significant reduction in radiated noise achieved across all frequency bands. By integrating the coil, Torex has also simplified the circuit layout for the designer and reduced the number of external components normally needed to implement this type of DC/DC solution. The smaller circuit layout also means less PCB tracking, which helps further reduce the radiated noise.

With a nominal 3.0MHz (± 15%) switching frequency as standard the output voltage can be fixed internally within a range of 0.8V to 3.6V in 50mV steps (accuracy: ± 2.0%). The XCL219 operates with fixed frequency PWM control whereas the XCL220 has automatic PWM/PFM switching control providing fast response, low ripple and high efficiency over the full range of load conditions (from light load to heavy load).

The XCL219/220 series include a 0.25ms high speed soft-start function for quick turn-on, a chip enable pin to turn the IC on and off and an optional CL discharge