ON Semiconductor unveils fixed-frequency ICs

Bangalore: ON Semiconductor, a supplier of silicon solutions for green electronics has launched the NCP1237, NCP1238 and NCP1288 fixed-frequency, current-mode controller ICs. Targeted at AC-DC adapter applications for laptop/notebook computers, LCD displays, printers, and household consumer electronics, the new controllers are available in a choice of frequency options with single or dual level over current thresholds.

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The standard device has a built-in 65kHz oscillator, with 100kHz and 133kHz versions supplied on request. According to the company, the proprietary Soft?Skip mode utilized by these ICs ramp the peak current gradually during skip mode, reducing the risk of audible noise. This allows additional component savings, along with easing the design and manufacture of the transformer. Combining this with a frequency fold-back function, the new controllers deliver high efficiency levels in light load conditions, while minimizing input power during no load conditions.

The Dynamic Self Supply (DSS) function of the NCP1237 and NCP1238 provide an integrated start-up current source that intelligently handles start-up and line transient events. This simplifies the design of the auxiliary supply, reducing the size of the VCC capacitor. To minimize external component count, the controllers integrate brown-out, over-power compensation and ramp compensation, allowing a compact solution to be designed. The new fixed-frequency, current-mode controller ICs have an operational temperature range of ?40 Celsius to 125 Celsius and are offered in a compact SOIC-7 package.