Features 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 Description 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 rDS_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. Applications Embedded power supplies for PC motherboards Triple DC/DC power supplies Programmable high current DC/DC power supply

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Datasheets

Title		Size	Date	Other Language
	LM2637 Motherboard Power Supply Solution with a 5-Bit Programmable Switching Controller and Two Linear Regulator Controllers	803 Kbytes	15-Nov-04	日本語

Application Notes

Title		Size	Date	Other Language
	AN-1145: Application Note 1145 Using Dynamic Voltage Positioning to Reduce the Cost of Output Capacitors in Advanced Microprocessor Power Supplies	134 Kbytes	10-May-04	中文

Obsolete Versions

Obsolete Part	Alternate Part or Supplier	Source	Last Time Buy Date
LM2637M	NONE	NATIONAL SEMICONDUCTOR	01 Dec 2009
LM2637MX	NONE	NONE	30 Nov 2009