Camarillo, Calif.—Semtech's SC190, for low noise battery powered applications, is a programmable DC/DC buck regulator with very low reflected (input) ripple—less than 1 mV back into the main supply rail.
"Next-generation portable devices are increasingly sensitive to noise on power rails, and at 1 mV, the SC190 has a five-times improvement over competing devices, which makes it a key component for
these systems," said Larry King, 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."
At higher output currents (guaranteed to 300 mA), the regulator operates in its pulse-width-modulation (PWM) switching mode for highest efficiency. The SC190, working at 1 MHz, can accept external clock signals to synchronize the switching frequency between 750 kHz to 1.5 MHz. At lower output currents, it operates in its linear regulator mode for highest efficiency. The device can be switched between modes by using the chip's 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 reflected (input) ripple to 1 mV, compared to the 10 mV typical in a PWM switching mode.
Under light load operation, the chip's back-end low dropout (BELDO) regulator can be dynamically selected to bypass the PWM switching circuitry. Quiescent current in this mode is approximately 10 microamps; output ripple is 90 microvolts RMS. Competitive architectures often use pulse-skipping or pulse-frequency modes to regulate the output during light load conditions, which according to the company creates orders of magnitude higher output ripple.
The SC190 is available in four versions that provide an output range of 1 to 2.8 volts. The chip has two-bit programmable capability, and thus the user can set output voltage without the need for a separate resistor divider. Basic protection include thermal shutdown when junction temperature reaches 150°C, an internal current limit of 500 mA on the front-end LDO to protect against a pulsed short-circuit, an over-voltage shutdown feature, and a soft-start mode that limits in-rush current during start-up.
Click here for the product datasheet. The SC190 comes in a 3-by-3 mm MLP-10 package that is lead free and meets worldwide environmental requirements, including the RoHS directive. It's priced at $1.05 to $1.20 each (depending on version) in 1k pieces.
Semtech Corp., 1-805-498-2111, www.semtech.com