LOWEST-COST USB CURRENT-LIMITED SWITCHES HAVE BEST PERFORMANCE
SUNNYVALE, CA-August 18, 1999-Maxim Integrated Products introduces the MAX1693/MAX1694 current-limited power switches for universal serial bus (USB), PCMCIA cards, and other hot-swap plug-in applications. These switches are the lowest-cost, highest-accuracy solution for current-limiting applications and are available in a space-saving 10-pin µMAX package (half the size of an 8-pin SO).
The devices prevent your PC system from crashing due to an overcurrent or short-circuit condition at the USB port. The maximum current the system power supply needs to deliver is the guaranteed 1A max. Other silicon solutions and polyfuses have only 50% accuracy, and the worst-case continuous current can be over 2A, requiring a much larger and more expensive system power supply. Even if the output is shorted, however, the MAX1693/MAX1694 have a fold-back scheme that reduces the current through the switch to only 500mA.
The MAX1693/MAX1694 generate a FAULT-bar signal when they reach current limit, thermal shutdown, or undervoltage lockout. They have an internal 10ms blanking period that prevents high-current transients from causing the FAULT-bar pin to go low. If the overcurrent condition continues beyond 10ms, the MAX1693 will set FAULT-bar low until the overcurrent is removed. The MAX1694 will latch FAULT-bar low and turn off the power switch to further protect the system power supply. Cycling the MAX1694 off/on resets the switch.
Quiescent current is a low 14µA in the on state and drops to only 0.1µA when the switch is off. Thermal overload protection automatically limits the power dissipation and junction temperature to safe levels. The parts are screened for the extended-industrial temperature range (-40°C to +85°C). Prices start from $0.80 (1000-up, FOB USA).
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