Power Electronics

Wide-Input Range Synchronous Buck Controller Platform

Semtech Corp. has expaned its line of high efficiency buck (step down) controllers with the addition of the SC418 and SC419 platform products. The SC419 is intended for operation in systems that have dual supplies, while the SC418 integrates a low dropout (LDO) regulator to enable operation from a single supply up to 28V. Both devices feature very strong gate drives (2A high side, 4A low side), and are optimized for low EMI and high efficiency over an extended load range. Efficiency enhancing features include Semtech's patent-pending ultrasonic power save with programmable floor frequency. Semtech's SmartDriveTM reduces EMI and eliminates the need for snubbers or gate drive resistors by adjusting the drive characteristics to the needs of specific MOSFETs.

The programmable LDO embedded in the SC418 can be used to provide the 5V necessary for the gate drive bias, allowing true single input rail operation. Internal crossover circuitry (another feature unique to Semtech's products) optimizes efficiency by bypassing the LDO after startup if the LDO and buck outputs are the same.

Semtech's Smart Power SaveTM technique enables the SC418 to re-enter continuous conduction mode when active loads attempt to pull the output high while in power save mode, pulling the output back down and avoiding over voltage latch-off.

Pseudo fixed frequency adaptive on-time control gives the parts superior transient response while reducing the output filter capacitance required and greatly simplifying the design process by removing external compensation components. The controller can be readily set up to allow output voltages up to 12V, will support full ceramic output capacitor solutions, and will start up into a pre-biased output. The strong gate drives provide enough current to power a single phase solution up to 30A.

The SC418 and SC419 have built-in soft-start, cycle-by-cycle current limiting, over-temperature, over-voltage and under-voltage protection features. They also include a power good output for the switching regulator, which may be used fo r diagnostics and sequencing.

The SC418 and SC419 are available immediately in production quantities and are priced at $0.86 for the SC418 and $0.79 for the SC419 each in 3,000-piece lots. Ordering codes for the parts are SC418ULTRT and SC419ULTRT.

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