LM2637  Product Folder

The LM2637 provides a comprehensive embedded power supply solution for motherboards hosting high performance MPUs such as M II™, Pentium™ II, K6-2 and other similar high performance MPUs. The LM2637 incorporates a 5-bit programmable, synchronous buck switching controller and two high-speed linear regulator controllers in a 24-pin SO package.

Switching Section - The switching regulator controller features a 5-bit programmable DAC, over-current and over-voltage protection, under-voltage latch-off, a power good signal, and output enable. The 5-bit DAC has a typical tolerance of 1%. There are two user-selectable over-current protection methods. One provides accurate over-current protection with the use of an external sense resistor. The other saves cost by taking advantage of the r_DS[lowbar]ON of the high-side FET. The over voltage protection provides two levels of protection. The first level keeps the high-side FET off and the low-side FET on. The second provides a gate signal that can be used to fire an external SCR.

Linear Section - The two linear regulator controllers feature wide control bandwidth, N-FET and NPN transistor driving capability, and an adjustable output voltage. The wide control bandwidth makes meeting fast load transient response requirement such as that of the GTL+ bus an easy job. In minimum configuration, the two controllers default to 1.5V and 2.5V respectively.

Both linear controllers have under voltage latch-off.

• Provides 3 regulated voltages
• Power Good flag and output enable
• Under-voltage latch-offSwitching Section
• Synchronous rectification
• 5-bit DAC programmable from 3.5V to 1.3V
• Typical 1% DAC tolerance
• Switching frequency: 50 kHz to 1 MHz
• Two levels of over-voltage protection
• Two methods of over-current protection
• Adaptive non-overlapping FET gate drives
• Soft start without external capacitorLinear Section
• N-FET and NPN driving capability
• Ultra fast response speed
• Output voltages default to 1.5V and 2.5V yet adjustable

• Embedded power supplies for PC motherboards
• Triple DC/DC power supplies
• Programmable high current DC/DC power supply