The TC1267 is an application-specific, low dropout regulator (LDO) specifically intended for use in PCI peripheral card applications complying with PCI Power Management (PCI 2.0). It provides an uninterrupted, 3.3V output voltage when the main (5V) or auxiliary (3.3V) input voltage supplies are present. The TC1267 consists of an LDO, a voltage threshold detector, external switchover logic and gate drive circuitry. It functions as a conventional LDO as long as the voltage on the main supply input (VIN) is above the lower threshold (3.90V typ). Should the voltage on VIN fall below the lower threshold the LDO is disabled, and an external P-channel MOSFET is automatically turned on, connecting the auxiliary supply input to VOUT, and ensuring an uninterrupted 3.3V output. The main supply is automatically selected if both the main and auxiliary input supplies are present, and transition from one input supply to the other is guaranteed glitch-free. High integration, automatic secondary supply switchover, Kelvin sensing, and small size make the TC1267 the optimum LDO for PCI 2.0 applications.

• Glitch-Free Transition Between Input Sources
• Automatic Input Source Selection
• External PMOS Bypass Switch Control
• Built-In 5V Detector
• Kelvin Sense Input
• Low Ground Current, Independent of Load