LM138 - LM238 - LM338 Three-terminal 5 A adjustable voltage regulators Features 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 % TO-3 Guaranteed thermal regulation Current limit constant with temperature protection remains functional even if the adjustment pin is accidentally disconnected. Standard 3-lead transistor package Normally, no capacitors are needed unless the Description device is situated far from the input filter capacitors in which case an input bypass is The LM138, LM238, LM338 are adjustable 3- needed. An optional output capacitor can be terminal positive voltage regulators capable of added to improve transient response. The supplying in excess of 5 A over a 1.2 V to 32 V adjustment terminal can be bypassed to output range. They are exceptionally easy to use achieve.very high ripple rejection ratios which are and require only 2 resistors to set the output difficult to achieve with standard 3-terminal voltage. Careful circuit design has resulted in regulators. outstanding load and line regulation comparable Besides replacing fixed regulators or discrete to many commercial power supplies. The LM138 designs, the LM238 is useful in a wide variety of family is supplied in a standard 3-lead transistor other applications. Since the regulator isfloatin package. and sees only the input-to-output differential A unique feature of the LM138 family is time-de- voltage, supplies of several hundred volts can be pendent current limiting. The current limit circuitry regulated as long as the maximum input to input allows peak currents of up to 12 A to be drawn differential is not exceeded. from the regulator for short periods of time. This The LM138, LM238, LM338 are packaged in allows the LM138 to be used with heavy transient standard steel TO-3 transistor package. The loads and speeds start-up under full-load LM138 is rated for operation from - 55 C to conditions. Under sustained loading conditions, 150 C, the LM238 from - 25 C to 150 C and the the current limit decreases to a safe value LM338 from 0 C to 125 C. protecting the regulator. Also included on the chip are thermal overload protection and safe area protection for the power transistor. Overload Table 1. Device summary Part numbers Order codes Temperature range LM138 LM138K -55 C to 150 C LM238 LM238K -25 C to 150 C LM338 LM338K 0 C to 125 C April 2008 Rev 2 1/23 www.st.com 23 Obsolete Product(s) - Obsolete Product(s)Contents LM138 - LM238 - LM338 Contents 1 Diagram . 3 2 Pin configuration . 4 3 Maximum ratings . 5 4 Electrical characteristics . 6 5 Typical characteristics . 8 6 Typical application . 12 7 Application hints . 13 7.1 External capacitors 13 7.2 Load regulation 14 7.3 Protection diodes . 14 8 Package mechanical data 20 9 Revision history . 22 2/23 Obsolete Product(s) - Obsolete Product(s)