Semtech’s 1MHz Controller Targets Telecom Converters
Semtech Corp. has added the SC4806, a dual-ended, pulse-width modulation (pwm) controller that features low power consumption and high speed that makes it ideal for designing compact high power isolated off-line and telecom power supplies.
The SC4806 has a 90uA start-up current and can be configured in either current mode or voltage mode. The controller can operate in peak current mode or in voltage mode by programming the slope compensation using a single external resistor. Operating in voltage mode feed forward allows fast line transient response and eliminates the need for current sensing elements.
The current mode control simplifies the loop dynamics and reduces transformer saturation problems in full-bridge and push-pull topologies. The SC4806 contains all of the control circuitry required for isolated applications where a secondary side error amplifier is used. Operating from telecom power rails (36V to 76V), the SC4806 can be used to design high current push-pull, half-bridge or full-bridge isolated power converters.
The SC4806 can be programmed using an external RC circuit to 1 MHz operating frequency. The two outputs operate 180-degrees out-of-phase and run at half the frequency. The controller also features SYNC that allows the oscillator to synchronize its clock to an external source. The SC4806 utilizes a unique oscillator that allows two SC4806 devices to be synchronized to provide automatic out-of-phase (bi-phase) switching, minimizing input and output current ripple and reducing the stress on, and size of input/output filter components.
"The SC4806 is the ultimate versatile pwm controller," said Ven Shan, Vice President of Marketing for Semtech's Power Management Products. "The feature set is augmented by a small package size, high operating frequency and high integration that can deliver high power density to isolated dc to dc converter designs for the networking, telecom and server markets."
The SC4806 has built-in pulse-by-pulse current limiting and auto-restart over-current protection in both current and voltage modes. Each SC4806 has a two channel half-bridge power circuit, with the flexibility to combine two devices in a full bridge design for systems needing up to 1,000W. This capability comes with programmable dead time between the two outputs that can be adjusted depending on the size of the timing components.
The SC4806 is available immediately in production quantities and is priced at $1.50 each in 1,000-piece lots.
