LM138 Three-terminal 5 A adjustable voltage regulators

The LM138, LM238, LM338 are adjustable 3-terminal positive voltage regulators capable of supplying in excess of 5 A over a 1.2 V to 32 V 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-de-pendent current limiting. The current limit circuitry allows peak currents of up to 12 A 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 far from the input filter capacitors in which case an input bypass is needed. An optional output capacitor can be added to improve transient response. The adjustment terminal can be bypassed to achieve.very high ripple rejection ratios which are difficult to achieve with standard 3-terminal regulators.

Besides replacing fixed regulators or discrete designs, the LM238 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 input differential is not exceeded.

The LM138, LM238, LM338 are packaged in standard steel TO-3 transistor package. The LM138 is rated for operation from - 55 °C to 150 °C, the LM238 from - 25 °C to 150 °C and the LM338 from 0 °C to 125 °C.

技术特性

Guaranteed 7 A peak output current
Guaranteed 5 A output current
Adjustable output down to 1.2 V
Line regulation typically 0.005 %/V
Load regulation typically 0.1 %
Guaranteed thermal regulation
Current limit constant with temperature
Standard 3-lead transistor package

内部原理图

LM138 订购信息

订购型号	产品状态	美金价格	数量	封装	包装形式	温度范围	材料声明
LM138K	Active		1000	TO-3	Poly Bag	-55 °C-150 °C	LM138K

DATASHEET

描述	版本	大小
LM138 : DS0521: Three-terminal 5 A adjustable voltage regulators	2	1596KB