LM138 Datasheet | Texas Instruments

Features - 1 Specified 7-A Peak Output Current - Specified 5-A Output Current - Adjustable Output Down to 1.2 V - Specified Thermal Regulation - Current Limit Constant With Temperature - P + Product Enhancement Tested - Output is Short-Circuit Protected 2 Applications - Adjustable Power Supplies - Constant Current Regulators - Battery Chargers Pin 1. Adjustment 2. Output 3. Input Tab/Case is Output Available Packages 3 1 TO-220 1 2 3 TO-3 Typical Application Circuit Copyright © 2016, Texas Instruments Incorporated 3 Description The LM138 series of adjustable 3-terminal positive voltage regulators is 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, parable to many mercial power supplies. The LM138 family is supplied in a standard 3-lead transistor package. A unique feature of the LM138 family is timedependent 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 (ADJ) 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 increases the ripple rejection of the regulator. Besides replacing fixed regulators or discrete designs, the LM138 is useful in a wide variety of other...