LM350 Adjustable Output, Positive Voltage Regulator

LM350 is an adjustable positive floating regulator chip capable of providing 1.2V to 33V and a fixed output voltage of 1.2 volts by connecting adjustment pin directly to ground. It takes an unregulated voltage signal and sends a stable, smooth and regulated voltage signal at the output pin. It can operate within a temperature range of – 40°C to + 125°C.  This IC is extremely simple to use and is accessible in different packages.

LM350 Pinout

LM350 pinout

Pinout Description

Pin NumberPin NameDescription
1ADJAdjustable pin adjusts the output voltage and gives the fixed voltage when grounded.
2Output pin gives the output voltage produced.
3Supply this pin with input voltage.

 Features

  • Delivers an output current of 3 Amps.
  • Output voltage is adjustable from 1.25V to 33V with 1% tolerance.
  • Provides a load regulation of 0.1% and a line regulation of 0.005%/V.
  • The chip can bear maximum input to an output voltage difference of 35V. For normal operation, it should be 15 volts.
  • It provides thermal regulation against overloads. The overload protection protects the chip and keeps performing its operation even if the adjust terminal is not connected or
  • Provides floating operation in high voltage applications.
  • It has built-in protection which protects the chip when the current exceeds beyond the rating by tripping the device.
  • Very high dissipation of around 85 watts.

Where to use it?

There are so many voltage regulator IC’s available which you can use in applications involving voltage regulation, but their output voltage range and output currents have different limitations. So, if you need an output current of 3A and voltage in a range of 1.25V to 33V then this IC would be suitable to use. It can perform a function of precision current regulator by connecting a fixed resistor between adjust and output terminals. Due to its adjustable output voltage capability, it is used in switching regulators and programmable regulators.

How to use LM350?

Most of the voltage regulators use an input and output capacitor. LM350 working is similar to other voltage regulators. You can change its output voltage from 1.25V to 33V by adjusting the values of resistors connected between adjustable and output pin. The output capacitor improves regulation and transient response. This device provides an extremely good load regulation. To maximize performance, the resistor R1 should be directly connected to the output to achieve good regulation.

Adjustable voltage regulator circuit

LM350T Adjustable voltage regulator example circuit

Diode protection is not needed for output voltages of less than 25V. When the output is greater than 25V, then connect protection diodes which prevent the discharging of capacitors through low current points. These diodes provide the discharging path for the capacitors. The R2 is a potentiometer. You can obtain the desired value at the output by varying the resistance of the potentiometer. The equation for calculating output voltage is :

 Vout= 1.25(1 +R2 /R1) +I(ADJ) x R2

To design a voltage supply with an electronic shutdown feature, clamp the adjust pin to the ground.

12V Battery Charger LM350

One of the major applications of this IC is a battery charger. Figure 4 shows a circuit of a simple 12V battery charger. Connect a resistor Rs between the output and R1. It sets the impedance of output.

LM350 battery charger circuit example

Application

The applications of positive voltage regulator LM350 include:

  • Battery chargers
  • Current Limited chargers
  • Switching Regulators
  • Temperature Controllers
  • Light Controller
  • Tracking Pre-regulator

LM2576 Equivalent and Alternative Options

2D Diagram

It is a 3 lead IC consisting of TO-220, SOT223, TO263 packages. The dimensions for the TO220 package are given in the table. For details about other packages, check the datasheet.

LM350T 2D Diagram

Datasheet

LM350 Datasheet

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