LM2638 - Motherboard Power Supply Solution with a 5-Bit Programmable Switching Controller and Two Linear Regulator Controllers [Life-time buy]
Datasheet Packaging Samples & Pricing Reliability Application Notes Knowledge Base

Features
Provides 3 regulated voltages
Power Good flag and output enable
Charge pump pinSwitching Section
Synchronous rectification
5-bit DAC programmable down to 1.3V
Typical ±1% DAC tolerance
Switching frequency: 50 kHz to 1 MHz
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 drive capability
Ultra fast response speed
Under voltage latch-off at 0.63V
Output voltages default to 1.5V and 2.5V yet adjustable

General Description


The LM2638 provides a comprehensive embedded power supply solution for motherboards hosting high performance MPUs such as Pentium™ II, M II™, K6™-2 and other similar high performance MPUs. More...


Applications


Embedded power supplies for motherboards
Triple DC/DC power supplies
Programmable high current DC/DC power supply
  Typical Application
click for larger image


  Additional Resources
Application Notes


Block Diagram


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Datasheet
RoHS Compliance Information Size in KbytesDate Click link below to Download
LM2638 Motherboard Power Supply Solution with a 5-Bit Programmable Switching Controller and Two Linear Regulator Controllers 165
Kbytes
26-Jun-99 Download
LM2638 Motherboard Power Supply Solution with a 5-Bit Programmable Switching Controller and Two Linear Regulator Controllers (Japanese)
116 Kbytes   Download

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Package Availability, Models, Samples & Pricing
Part NumberPackageFactory Lead TimeModelsSamples &
Electronic
Orders
Budgetary PricingStd
Pack
Size
Package
Marking
Format
TypePinsSpec.MSL
Rating
Peak
Reflow
RoHS
Report
CAD
Symbols
WeeksQtyQty$US each
LM2638MSOIC WIDE24STD3260RoHS Download Lifetime buyN/A
 
Buy Now
1K+$2.10rail
of
30
NSUZXYTT
LM2638M
16 weeks500

Obsolete Versions

Obsolete PartAlternate Part or SupplierSourceLast Time Buy Date
LM2638M
NONE
NATIONAL SEMICONDUCTOR
01 Dec 2009

General Description


The LM2638 provides a comprehensive embedded power supply solution for motherboards hosting high performance MPUs such as Pentium™ II, M II™, K6™-2 and other similar high performance MPUs. The LM2638 incorporates a 5-bit programmable, synchronous buck switching controller and two high-speed linear regulator controllers in a 24-pin SO package. In a typical application, the switching controller supplies the MPU core, and the linear regulator controllers supply the GTL+ bus and the clock or graphics chip core. A charge pump pin helps provide the necessary voltage to power the linear sections when 12V is shut off during system standby such as STR mode.

Switching Section - The switching regulator controller features an Intel-compatible, 5-bit programmable output voltage, over-current and over-voltage protection, a power good signal, and a logic-controlled output enable. 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[lowbar]ON of the high-side FET. When there is an over voltage, the controller turns off the high side FET and turns on the low side.

Linear Section - The two linear regulator controllers feature wide control bandwidth, N-FET and NPN transistor driving capability and an adjustable output. The wide control bandwidth makes meeting the GTL+ bus transient response requirement an easy job. In minimum configuration, the two controllers default to 1.5V and 1.25V respectively.

Both linear controllers have under voltage latch-off.

Reliability Metrics


Part Number Process EFR Reject EFR Sample Size PPM LTA Rejects LTA Device Hours FITS MTTF (Hours)
LM2638MABCD15003417500423400011201409060

Note: The Early Failure Rates (EFR) were calculated as point estimate PPM based on rejects and sample size for EFR. The Long Term Failure Rates were calculated at 60% confidence using the Arrhenius equation at 0.7eV activation energy and derating the assumed stress temperature of 150°C to an application temperature of 55°C.

For more information on Reliability Metrics, please click here.


More Application Notes


TitleSize in Kbytes Date Click link below to Download
AN-1146: Application Note 1146 Designing a Multi-phase Asynchronous Buck Regulator Using the LM2639 127
Kbytes
10-May-04 Download
AN-1208: Application Note 1208 LM2633 Evaluation Board 700
Kbytes
10-May-04 Download

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[Information as of 8-Nov-2009]