Semtech Corporation SC1532
the SC1532 is designed to maintain a glitch-free 3.3V output when at least one of two inputs, 5V (VIN1) and 3.3V (VIN2), is present. The SC1532 combines a 5V to 3.3V linear regulator with an integral 3.3V bypass switch, along with logic and detection circuitry to control which supply provides the power for the output. When VIN1 falls below a lower threshold value, the NMOS pass device is turned on and the PMOS linear regulator is turned off.DESCRIPTION
Intended for applications such as Power Managed PCI, Whenever VIN1 exceeds a predetermined threshold value, the internal 3.3V PMOS linear regulator is enabled, and the internal pass NMOS is turned off. This ensures an uninterrupted 3.3V output even if VIN1 falls out of specification. When both supplies are simultaneously available, the PMOS linear regulator will be turned on, and the NMOS pass will be turned off, thus preferentially supplying the output from the 5V supply. The internal 5V detector has its upper threshold (for VIN1 rising) set to 4.18V (typical) while the lower threshold (for VIN falling) is at 4.1V (typical) giving a hysteresis of approximately 80mV. The SC1532 is available in the popular SO-8 surface mount package.FEATURES
● Glitch-free transition between input sources● Internal logic selects input source
● 5V detector with hysteresis
● 1% regulated output voltage accuracy
● 400mA load current capability
APPLICATIONS
● Desktop Computers● Network Interfa...