Features • Guaranteed 7A peak output current • Guaranteed 5A output current • Adjustable output down to 1.2V • Guaranteed thermal regulation • Current limit constant with temperature • P+ Product Enhancement tested • Output is short-circuit protected Description The LM138 series of adjustable 3-terminal positive voltage regulators is capable of supplying in excess of 5A over a 1.2V to 32V output range. They are exceptionally easy to use and require only 2 resistors to set the output voltage. Careful circuit design has resulted in outstanding load and line regulation-comparable to many commercial power supplies. The LM138 family is supplied in a standard 3-lead transistor package. A unique feature of the LM138 family is time-dependent current limiting. The current limit circuitry allows peak currents of up to 12A to be drawn from the regulator for short periods of time. This allows the LM138 to be used with heavy transient loads and speeds start-up under full-load conditions. Under sustained loading conditions, the current limit decreases to a safe value protecting the regulator. Also included on the chip are thermal overload protection and safe area protection for the power transistor. Overload protection remains functional even if the adjustment pin is accidentally disconnected. Normally, no capacitors are needed unless the device is situated more than 6 inches from the input filter capacitors in which case an input bypass is needed. An output capacitor can be added to improve transient response, while bypassing the adjustment pin will increase the regulator's ripple rejection. Besides replacing fixed regulators or discrete designs, the LM138 is useful in a wide variety of other applications. Since the regulator is "floating" and sees only the input-to-output differential voltage, supplies of several hundred volts can be regulated as long as the maximum input to output differential is not exceeded, i.e., do not short-circuit output to ground. The part numbers in the LM138 series which have a K suffix are packaged in a standard Steel TO-3 package, while those with a T suffix are packaged in a TO-220 plastic package. The LM138 is rated for -55°C < TJ < +150°C, and the LM338 is rated for 0°C < TJ < +125°C. Applications • Adjustable power supplies • Constant current regulators • Battery chargers

Also Recommended LM2677 No Heatsink Required , On/off Pin LM2678 No Heatsink Required LM2679 No Heatsink Required , Adjustable Current Limit MY BRIEFCASE                                       Click any "Briefcase" icon to add an item

Typical Application *click for larger image	Connection Diagram *click for larger image
Typical Performance *click for larger image

Datasheets

Title		Size	Date	Other Language
	LM138/LM338 5-Amp Adjustable Regulators	396 Kbytes	3-Mar-99	日本語

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Part Number(s) (NSID)	Top View	Availability	Current Reported Stock	Budgetary Pricing	Standard Pack Size
LM338T/NOPB LM338T RoHS Status	TO-220	Full production Lead Time: 16 weeks	Distributor Region Qty ARROW Worldwide 200 AVNET-EM Worldwide 1033 DIGIKEY Worldwide 2201 FARNELL Europe and Asia 4255 FUTURE Worldwide 1100 NEWARK Americas 3527 RS COMPONENTS Worldwide 125 TAYLOR Americas 3961	$0.93 each at 1K+ pcs	rail of 45
LM338K STEEL/NOPB LM338K STEEL RoHS Status	TO-3	Full production Lead Time: 6 weeks	Distributor Region Qty ARROW Worldwide 91 AVNET-EM Worldwide 161 DIGIKEY Worldwide 49 FARNELL Europe and Asia 1238 FUTURE Worldwide 128	$32.20 each at 250+ pcs	tray of 50
LM338 MWC RoHS Status		Full production Lead Time: 6 weeks	Contact your distributor	CALL	wafer jar of N/A

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National's certificate of product compliance is located at RoHS Status.

All information pertaining to the RoHS Compliance Standard can be found at http://www.national.com/packaging/leadfree.

A RoHS compliance or an IPC 1752 report can be acquired at http://www.national.com/quality/green.

National's certificate of product compliance is located at RoHS Status.

CAD Symbols and Models N/A

Models N/A

Reliability Metrics

Part Number	Process	EFR Reject	EFR Sample Size	PPM	LTA Rejects	LTA Device Hours	FITS	MTTF (Hours)
LM338T	SLM	0	44046	0	0	3532500	1	1002356520

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.

All information pertaining to the RoHS Compliance Standard can be found at http://www.national.com/packaging/leadfree.

A RoHS compliance or an IPC 1752 report can be acquired at http://www.national.com/quality/green.

National's certificate of product compliance is located at RoHS Status.