Semtech Debuts Buck Regulator with Under 1mV Supply Ripple
The SC190, a programmable dc-dc step-down (buck) regulator that features under 1mV supply ripple, for noise sensitive, battery-powered portable applications is now available from Semtech Inc.
The SC190's flexibility comes from its dual-mode capability. At higher output currents, best efficiency is achieved operating in pulse-width-modulation (pwm) switching mode while at lower output currents, efficiency is higher in the linear regulator mode. The device can be easily switched between modes by using the mode select pin.
As a linear regulator, the SC190 features an integrated front-end low dropout (FELDO) pre-regulator designed to filter incoming power signals. This lowers the input ripple noise to 1mV compared to the 10mV typical in a pwm switching mode. Low input ripple performance is very desirable for cell phones and many other RF or wireless applications where a noisy power supply can degrade system performance.
Ideal for light load operation, an integrated back-end low dropout (BELDO) regulator can be dynamically selected to bypass the PWM switching circuitry. This achieves device quiescent current of approximately 10µA with low output voltage ripple of 90µV rms (typical). Competitive architectures often use pulse-skipping or pulse-frequency modes to regulate the output during light load conditions, which creates orders of magnitude higher output ripple.
"Next-generation portable devices are increasingly sensitive to noise on power rails, and at 1mV, the SC190 has a five-times improvement over competing devices, which makes it a key component for these systems," said Larry King, Semtech's Vice President of Power Management for Handheld Products. "There are no sacrifices for this low noise, as the SC190 is highly integrated, meets the need for low power consumption and takes up very little space."
The SC190 has a built-in 1MHz-switching mode, or can accept external clock signals to synchronize the switching frequency between 750kHz to 1.5MHz.
The SC190 is available in four voltage variants that provide a voltage range of 1.0V to 2.8V. With two-bit programmable output voltage capability, the necessary output voltage can be selected without need of a separate resistor divider. This feature eliminates two discrete resistors from a typical design, reducing board complexity, board space requirements and overall cost.
The SC190 offers protection features including a thermal shutdown that shuts the device off when junction temperature reaches 150 °C, an internal current limit of 500mA on the front-end LDO to protect against a pulsed short circuit, an overvoltage shutdown feature, and a soft-start mode that limits in-rush current during start-up.
The SC190 comes in a 3mm by 3mm MLP-10 package that is lead free and meets worldwide environmental requirements including the European Union's Restriction on Hazardous Substances in Electrical Equipment (RoHS) directive. The SC190 family of products is available immediately in production quantities. SC190 variants are priced between $1.05 and $1.20 each in 1,000-piece lots.
