SOT23 UNIVERSAL OFFLINE POWER-SUPPLY CONTROLLER TARGETS STANDBY POWER SUPPLIES AND CELL-PHONE CHARGERS
SUNNYVALE, CA-September 27, 2001-Maxim Integrated Products introduces the MAX5021 and MAX5022, the industry’s first SOT23 power-supply controllers for use in power supplies operating from the universal offline voltage range of 85VAC to 265VAC. DC input voltage range is 24V to 375V. The devices drive an external N-channel MOSFET, allowing designers to optimize price/performance trade-offs such as size, efficiency, and cost. With a 250kHz switching frequency and a minimum number of external components required, these devices can operate with surface-mount as well as planar transformers, allowing design of compact isolated power supplies.
The MAX5021/MAX5022 feature ultra-low 50µA startup current, which allows the use of a high-value 1/4W startup resistor and a 0.22µF ceramic start-up capacitor. This allows fast power-supply startup while the startup resistor dissipates only 40mW when operating from a rectified 120VAC line. After power-up, the MAX5021/MAX5022 derive their power from a low-voltage auxiliary winding off the transformer. Coupled with only 2mA operating current, power-supply efficiency up to 80% can be achieved when delivering 5W at 120VAC input. The MAX5021 operates at 50% maximum duty cycle and is recommended for forward-converter isolated power supplies capable of up to 10W output power.
The MAX5022 operates at 75% maximum duty cycle and is recommended for flyback isolated power supplies capable of over 15W output power.
These devices are targeted at energy-efficient PCs, VCRs, TV sets, fax machines, and set-top boxes that switch to a low-power, high-efficiency standby power supply when in standby mode. The MAX5021/MAX5022 are also ideal for mobile phone chargers and compact low-power wall adapters. A fully tested 5V/1A universal offline power-supply evaluation kit is available to speed designs.
Rated for operation at the extended temperature range (-40° C to +85°C), the MAX5021/MAX5022 are available in the surface-mount 6-pin SOT23, 8-pin µMAX, and 8-pin DIP packages. Prices start at $0.67 (1000-up, FOB USA).
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