Summary of How to Select a Voltage Regulator
This article explains the role of voltage regulators within Power Management ICs (PMICs) for maintaining stable DC power from batteries or mains. It details key selection parameters including output voltage, accuracy, load current, efficiency, and dropout voltage, using the Texas Instruments TPS76733 as a specific case study to illustrate how these factors influence project success.
Parts used in the Voltage Regulator Selection Project:
- Batteries
- Mains AC voltage sources
- Power Management ICs (PMICs)
- Voltage regulators
- Texas Instruments TPS76733
- Capacitors
- Resistors
- Inductors
- Connectors
- MCUs
All electronics projects need power. Power can come from either stored energy in a battery, or directly from mains AC voltage or DC power from renewable sources such as solar energy. Power Management ICs (PMICs) help manage the power requirements in a system including scaling voltages, battery charging, and DC-DC conversion. Choosing the right PMIC can make a difference in whether the final product becomes successful or not. An integral part of any PMIC solution is a voltage regulator. Voltage regulators provide a constant output voltage from a higher or lower input voltage. In this blog, let’s look at the variety of voltage regulators, how to choose them, and how Octopart data can help you make the decision to choose the right voltage regulator for your project. This is a follow-up on our series of blogs on how to select a capacitor, resistor, inductor, connector, IC packages and MCUs.
Voltage Regulators
Voltage regulators provide a stable DC voltage during operation of a system. Voltage regulators can receive power from either mains AC voltage from wall outlets or from batteries in electronic devices. Batteries discharge almost linearly with time and voltage regulators are needed to maintain stable power supply for electronic systems. This can be seen below:
In addition to powering circuits, a precise DC voltage is often used as a reference to which voltage signals are compared to make decisions. If this reference voltage is not very stable and fluctuates a lot, it affects the decision making of a system. NOTE: Input voltage and supply voltage are sometimes used interchangeably, as voltage regulators use supply voltage as their input.
Let’s dive into some of the most common parameters that are used to choose a voltage regulator. We’ll take Texas Instruments’ TPS76733 as an example to learn about the parameters that drive the decision to choose a particular regulator.
IMPORTANT PARAMETERS:
- Output voltage: Output voltage is the constant voltage that you expect the voltage regulator to regulate voltage at. A regulator takes a noisy input and regulates it to a particular voltage, for example, 3.3V.
- Accuracy: Accuracy refers to how much the output voltage changes across temperature and load current.
- Load current: Load current refers to the maximum output current expected from the voltage regulator by the load system.
- Efficiency: The efficiency of a regulator is given by a ratio of output power to input power which is proportional to the ratio of output voltage to input voltage. Dropout voltage of a regulator limits how close the output can be to the input. The lower the dropout voltage, the more efficient the linear regulator will be. Switching regulators have a theoretical hundred percent efficiency, but is in practice limited by the resistance of FET switch, diode voltage drop and ESR of both inductor and output capacitor.
- Dropout voltage: Dropout voltage is only applicable for linear regulators. It is the smallest possible difference between output and input supply voltage while remaining in the intended operating range of the voltage regulator. For TPS76733, the dropout voltage is 350 mV. For getting the correct output of 3.3V, input voltage has to be at least 3.65V as can be seen below:
Read more: How to Select a Voltage Regulator
- How do voltage regulators maintain system stability?
Voltage regulators provide a stable DC voltage during operation by taking noisy input and regulating it to a constant value. - Can voltage regulators receive power from batteries?
Yes, they can receive power from batteries which discharge almost linearly with time. - What is the primary function of a precise DC voltage reference?
A precise DC voltage is often used as a reference to compare voltage signals for making system decisions. - Which parameter measures how much output voltage changes across temperature?
Accuracy refers to how much the output voltage changes across temperature and load current. - Does dropout voltage apply to switching regulators?
No, dropout voltage is only applicable for linear regulators. - What is the minimum input voltage required for the TPS76733 to output 3.3V?
The input voltage has to be at least 3.65V because the dropout voltage is 350 mV. - What limits the theoretical efficiency of switching regulators?
Practical efficiency is limited by the resistance of the FET switch, diode voltage drop, and ESR of both inductor and output capacitor. - How does Octopart assist in choosing a regulator?
Octopart data helps you make the decision to choose the right voltage regulator for your project.
