Synchronous step-down power supply controller

Semtech has released the SC1470 synchronous buck power supply controller.

Semtech has released the SC1470 synchronous buck power supply controller.

A wide input supply range, fast transient response, small size, and high efficiency operation make the device ideal for use in many designs, including notebook chipsets and LCDs as well as network power supplies and other embedded applications.

Featuring a 4.5 to 25V input supply range, the SC1470 can operate directly from either the battery/AC adapter input of a notebook computer or from a system 5V supply.

The output voltage can be programmed within the 0.5 to 5V range, making the device ideal for chipset voltages, graphics core voltages and other power requirements in microprocessor-based applications.

The strong 1A gate drive easily supports applications with load currents as high as 10A.

The SC1470 uses a constant-on-time approach to regulation.

By eliminating the error amplifier typically found in PWM controllers, the associated time lags are also eliminated, thereby providing extremely fast transient response.

Removing the error amplifier also enhances control loop stability, simplifying the design process.

Under steady-state conditions, the SC1470 operates at a fixed frequency.

During a load or line change, the frequency changes to accommodate the transient event, with fixed frequency operation resuming once the transient event has passed.

Designers can program the operating frequency anywhere within the device's 100 to 600kHz range, simply by changing resistors.

This feature provides designers with the flexibility to optimise their design for efficiency, output filter size, or position the frequency outside the range of interference with other sensitive circuitry.

The SC1470 provides other attractive design features, including: a selectable power-save mode that enables efficiencies higher than 90% at 100mA; RDS(on) current sensing to improve efficiency and reduce cost by eliminating a sense resistor; and a low quiescent current (typically 700uA in operation) to maximise battery life.

Other features include: excellent line (0.04%/V) and load (0.3%) regulation; overcurrent, overvoltage and overtemperature protection; undervoltage lockout; and a power-good indication that can control downstream circuitry or sequence other power supplies.

The SC1470 is designed to operate over the full industrial temperature range of -40 to +85C.

Evaluation samples of the SC1470 are available now in TSSOP-14 packaging, with full production units available in November 2001.

Pricing begins at $2.65 in production quantities of 1000 pieces.

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