Recommended Components
The following parts are used in this article, along with a generic electronics kit that is handy for building and testing the circuit.
| Component | How it’s used | Buy on Amazon |
|---|---|---|
| LM1084 5A LDO regulator | The LM1084 5A low-dropout adjustable voltage regulator this article covers. | Check Price |
| Electronic component assortment kit (1390 pcs) | A handy assortment of resistors, capacitors, LEDs, diodes and transistors for building circuits. | Check Price |
| Digital multimeter (AstroAI) | Measures voltage, current, resistance and checks continuity while you build and debug. | Check Price |
| Breadboard | Solderless base for prototyping the circuit. | Check Price |
| Jumper Wires | Make the connections on the breadboard. | Check Price |
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LM1084 Pin Configuration
Pinout diagram presents that the voltage regulator has three pins. This pin assignment makes it easy to use for power supply and battery charging applications.
It has three pins in total.- Pin#01: Input pin of the voltage regulator
- Pin#02: Output pin of the voltage regulator
- Pin#03: Adjustable pin connected to two resistors in case of variable voltage and connected to ground in case of fixed voltage.
Features
The features and technical specifications of the LM1084 chip are:- It can provide fixed voltages of 3.3V, 5V and adjustable voltage in a range of 0V to 29V.
- Output current = 5A.
- The load and line regulations are 0.015% and 0.1%.
- 75 dB ripple rejection.
- Its operation is specified in a temperature range of -65 °C to 150 °C.
- Internal current limiting and thermal protection functions
Where to use LM1084?
This IC is versatile in its applications. You can use this chip in programmable output regulation and local on-card regulation. It can function as a precision current regulator by connecting a fixed resistor between the adjust and output pins. In other standard three-terminal regulators, it is very difficult to achieve a high ripple-rejection ratio. But the adjust pin of this chip can be bypassed which leads to a high rejection ratio.How to use LM1084?
It is a regulator IC which has a maximum voltage drop of 1.5V. The LM1084 IC is used in two modes which are fixed voltage and adjustable version. In the case of fixed voltage devices, the resistors R1 and R2 shown in the circuit diagram below are integrated inside the devices.Adjustable output voltage circuit Example
In an adjustable voltage version, the voltage drop across resistor R2 adds to the reference voltage of 1.25V developed between output and adjust pin. This combined voltage is used to set the desired voltage at the output.
In some adjustable voltage applications, an additional capacitor is connected between adjust pin and ground. This capacitor is used to increase the ripple rejection. The output capacitor improves the transient response. In applications which require large changes in output current, a large value capacitor is used. For a ripple rejection, connect a capacitor parallel with R2 in figure 3. It smooths out the ripples from the output and removes the excess noise.Battery Charger Circuit Example
It can be used as a battery charger where LM1084 IC acts as a constant voltage, constant current part. It senses the voltage potential across the battery and compensates it for the current-voltage. The regulator IC delivers the maximum current which is used to charge the battery. When the battery is near the fully charged state, the voltage potential across Rs and the regulator reduces the current in order to maintain the battery voltage. The circuit diagram is given below.
Equivalents and Alternatives
LM1085, LM317, LM723, LM7912LM1084 Applications
Some uses of this versatile IC are listed below:- It is used in Switching DC to DC Converters as a post regulator.
- Their high efficiency makes them suitable for use as linear regulators.
- They are also used for implementing battery charger circuits.
