How to Choose a Voltage Regulator: 6 Factors to Consider

Voltage regulators are an essential component in electrical and electromechanical devices to provide reliable performance. Electronics require consistent input voltage, and voltage regulators ensure that those requirements are met.

What is a Voltage Regulator Used For?

Everything from cars to air conditioners to cellphones use voltage regulators. Some devices are more sensitive than others and some power sources fluctuate more than others, making it tricky to selecting the best voltage regulators for each application.

Even in a simple design with a low power draw and relatively consistent power source, skipping a voltage regulator may compromise reliability. A basic light is one instance in which you may not require a voltage regulator because if the voltage drops, the light will simply dim. However, the lack of a voltage regulator could compromise performance and reliability, potentially causing such issues as LED flicker, controller resets and even “fried” electronics.

How Does a Voltage Regulator Work?

Voltage regulators are usually found where voltage needs to be fine-tuned. For example, in a wireless phone, you may have an AC adapter that converts 120VAC power down to 8VAC. Then, inside the base of the phone, you’ll find a voltage regulator to provide the required DC voltage to the electronics in the base. In the phone itself, you might find a DC-to-DC adapter that uses a voltage regulator to provide the correct voltage for the electronics in the handset.

In a complex electromechanical device with different components that require different voltages, the need for voltage regulators is more obvious. For example, a computer would use a wall plug adapter to convert 120VAC down to lower voltage. Then the different internal components such as the motherboard, cooling fan and hard drive require a specific voltage to function. Voltage regulators would be used to provide consistent, reliable voltage to each internal component.

Voltage Regulator Selection Guide

Consider these factors when selecting a voltage regulator:

1. Input Voltage and Output Voltage

Ideally, you know the input voltage range and the required output voltage that you will be working with. Each voltage regulator chip is designed to be used for a specific output voltage. For example, in a device running off 120VAC power that has a 5V Raspberry Pi controller, 12V servo motors and a 24V stepper motor, you would need to use 5V, 12V and 24V voltage regulators to ensure that everything runs smoothly.

However, if you’re stocking a supply to have on hand for a variety of uses, you can find adjustable output regulators that can be used for a range of outputs by making a simple adjustment.

The MCP1754ST-5002E/MC by Microchip is a good product example.

2. Dropout Voltage

Dropout is the minimum buffer between the output and input voltages. For example, if you have a 7V input and require 5V output, then a minimum 2V dropout is needed. If you suspect that the 7V input will drop below 7V, then you need a lower dropout.

Dropout is specified for each voltage regulator chip along with the output voltage. For example, you can find 5V voltage regulators with a range of available dropouts. For circuits with a small difference between the input and output voltage, a low-dropout voltage regulator (LDO) or even an ultra-low voltage regulator would be required.

The TCR2LE31,LM by Toshiba is a good product example. 

3. Linear Regular or Switching Regulator?

A linear regulator cannot compensate for power that drops below the output voltage. To provide 5V of output, a minimum of 5V must be maintained from the input voltage and the dropout of the linear voltage regulator. If power drops must be compensated for, then a boost or step-up switching regulator can be used.

The MIC2877-5.25YFT-TR by Microchip is a good product example. 

Another instance when a switching regulator could be beneficial is when spikes in power consumption could cause voltage to drop. For example, when a solenoid kicks in, power consumption spikes, voltage drops and your microcontroller resets unless you’re using a voltage regulator that can compensate.

Switching regulators may also make more sense for devices when there is a big difference between the input and output voltages, resulting in too much power lost/heat generated.

Whether or not using switching regulators makes sense depends on the type of project, design constraints and budget. Switching regulators can cause noise and interference that require compensation in the circuitry. Cost is also a factor. For an expensive robotics component or sensitive medical equipment, using switching regulators will be less of a cost issue than in a low-budget commodity item.

See DC to DC Converter and Switching Regulator Module and Types of Switching DC to DC Converters for more information.

4. Device Sensitivity

Highly sensitive devices such as smartphones, wireless devices, and battery-powered medical equipment may require a specific regulator to reduce noise. See Using LDOs to Minimize Power Noise for more information.

5. Response Time

For applications that require a fast response time such as graphics cards, televisions, computers, printers and embedded systems, specialty voltage regulators are available with fast response times.

The NCV51198PDR2G by ON Semiconductor is a good product example.

6. Power Draw

When using a linear voltage regulator, the difference between the input voltage and the output voltage is lost by converting it to heat. When power consumption is low, the heat generated is most likely not an issue. However, depending on the application, if the current drawn gets high enough, the amount of heat generated might become a problem. The above-mentioned option of using a switching regulator instead of a linear regulator is one possible solution. You can also use a heatsink to stay within the optimal temperature range.

While voltage regulators appear simple at first, they’re part of the larger, more complex power supply and electronics reliability picture. For assistance with design and troubleshooting, Arrow offers a comprehensive range of engineering services. Underestimating the potential reliability and performance issues that could result from an incorrect voltage regulator is an avoidable mistake that can be prevented with design expertise.

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