Semtech Broadens Power Management Portfolio With Compact Dual Synchronous Buck Power Supply Controller For Double Data Rate (DDR) Memory Systems in Portable Computers

Semtech Corp. (Nasdaq:SMTC), a leading supplier of analog and mixed-signal semiconductors for communications, portable devices, computers, and industrial equipment, today announced availability of the SC1486 Dual Synchronous DDR Buck Power Supply Controller. Targeting notebook computers, webpads and embedded applications, the SC1486 provides a complete power management solution for applications that utilize DDR memory. The SC1486 combines greater than 90 percent conversion efficiency, advanced features, and a small TSSOP-28 package to help system architects build compact and power-efficient portable computing systems.

The SC1486 accommodates a broad input voltage (VIN) range of 1.8V to 25V, enabling the device to directly interface with a wide array of standard battery configurations and a/c adapters. Provided are two independently programmable output voltages (VOUT) that can be adjusted from 5.5V down to 0.5V, allowing the device to meet anticipated sub-1V requirements for future chipset and peripheral voltages. To support DDR memory systems, Switcher #1 can be used to generate 2.5V for the memory chip supply (VDDQ), while Switcher #2 can be provided with a 1.25V floating (external) reference to support DDR active termination requirements (VTT). The device also provides a 1.25V, 3mA buffered reference (VREF) output.

To maximize battery life, the SC1486 incorporates power saving features. Switcher #1 provides a power-save mode that reduces the switching frequency under light-load conditions and thereby minimizes switching losses. Switcher #2 includes an S3 standby mode that shuts the switcher off, but leaves the buffered VREF output on, to reduce quiescent power consumption during a Suspend-to-RAM condition. With both switchers operating, the device has a quiescent current of 1250uA (typical), dropping to 750uA when switcher #2 is in standby mode.

"The SC1486 is a compact, flexible, highly efficient, and feature-rich power supply controller," said Semtech’s Director of Portable Power Management Products, Eddie Yeow. "The new device will be extremely enticing to designers of portable computing systems."

The SC1486 uses a constant on-time controller design, which yields inherently fast transient response and therefore helps reduce bulk capacitance requirements. The output frequency of the device can be programmed from 300 kHz to 600 kHz by simply changing resistors, allowing designers to optimize their designs for efficiency, output filter size, or to select a frequency that minimizes interference with other circuitry. Another key feature is the integrated gate drivers, which provide a two-stage "soft" turn-on to reduce overshoot and ringing, which in turn, reduces the occurrence of EMI-induced transients and switching noise. Lastly, the SC1486 uses the RDS (on) of the low-side MOSFETs for current sensing, which improves efficiency and reduces cost.

By integrating several output voltages into a single package, the SC1486 is ideal for DDR designs where saving space is critical. For applications where physical or other design constraints prevent use of an integrated device, please refer to Semtech’s SC1470 (2.5V VDDQ) and SC1480 (1.25V VTT and VREF).

Key Features of the SC1486

• DDR memory support
• Constant on-time design for fast transient response
• Two programmable output voltages from 0.5V to 5.5V
• Programmable output frequency from 300 kHz to 600 kHz
• Integrated output drivers with "soft" activation to reduced switching noise
• RDS(on) current sensing for improved efficiency and reduced costs
• Power saving features for longer battery life

Pricing and Availability

The SC1486 is available in volume production, and sells for $4.28 each in 1,000-unit quantities with a 12-week lead time. Evaluation samples are also available through Semtech’s network of direct sales representatives and distributors. Datasheets can be accessed at www.semtech.com.

About Semtech

Semtech Corporation is a leading supplier of high-quality analog and mixed-signal ICs for power management, over-voltage and transient protection, human interface devices & system management, test & measurement applications, and advanced communications. Publicly traded since 1967, Semtech is listed on the NASDAQ National Market under the symbol SMTC. For more information, contact Semtech Corporation at 200 Flynn Road, Camarillo, CA. 93012-8790; phone (805) 498-2111; email to info@semtech.com; or visit its Web site at www.semtech.com.