Sunnyvale, Calif. - Maxim Integrated Products' MAX1549 is a dual, PWM step-down controller that generates a dynamically adjustable 0.5 to 2 volts (main output) and a 0.5 to 2.7 volt or 1.8/2.5 volt fixed output (second output) for supplies powering low-voltage chipsets and RAM in notebook computers. It uses a single-stage buck conversion that allows the device to directly step down high-voltage batteries for highest efficiency, as opposed to typical applications that require a two-stage conversion from another system supply rail instead of the battery. Its fixed-frequency (100 kHz to 400 kHz in four steps, selectable) current-mode PWM architecture does not require complex compensation. The outputs of the step-down regulators are interleaved, minimizing input-capacitor requirements.
These Quick-PWM controllers are free running and have constant on-time with input feed-forward. This configuration is designed to provide ultra-fast transient response, wide input-output differential range,
low supply current, and tight load-regulation characteristics. The controllers accurately sense the inductor current across an external current-sense resistor in series with the output to ensure reliable overload and inductor-saturation protection. Alternatively, the
controllers can use the synchronous rectifier itself or lossless inductor current-sensing methods to provide overload protection with lower power dissipation.
The MAX1549 is available in a 40-pin TQFN package with optional inductor-saturation protection, and undervoltage/overvoltage protection. It is screened for the extended temperature range (-40 to +85°C). Prices start at $3.75 (1000-up, FOB USA). An evaluation kit is available with recommended external components to speed designs.