SC1532

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

Application

• Desktop Computers
• Network Interface Cards (NICs)
• PCMCIA/PCI Interface Cards
• Peripheral Cards

Pinout




Specifications

Parameter	Symbol	Maximum	Units
Input Supply Voltage	VIN,VIN2	-0.5 to +7	V
Charge Pump Capacitor Pin Voltage	CP	-0.5 to +16	V
Output Current	IO	400	mA
Operating Ambient Temperature Range	TA	-5 to +70	°C
Operating Junction Temperature Range	TJ	-5 to +125	°C
Storage Temperature Range	TSTG	-65 to +150	°C
Lead Temperature (Soldering) 10 sec	TLEAD	300	°C
Thermal Impedance Junction to Ambient(1)	JA	65	°C/W
ESD Rating (Human Body Model)	ESD	4	kV

Description

Intended for applications such as Power Managed PCI, 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.

Whenever VIN1 exceeds a predetermined threshold value, the internal 3.3V PMOS linear regulator is enabled, and the internal pass NMOS is turned off. When VIN1 falls below a lower threshold value, the NMOS pass device is turned on and the PMOS linear regulator 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.