Voltage regulators and DC converters are considered two of the most essential devices for electronic engineers today.
They are primarily used to control and regulate potentially unstable power supplies and to provide a controlled voltage suitable for devices such as microcontrollers and microprocessors.
Learning to identify these parts can be helpful when identifying power rails and whether they work correctly.
Linear Voltage Regulators Vs. DC Converters
Linear voltage regulators are easier to identify than DC converters because they typically have only three pins. You can recognize them by their U or IC designations and the two formats they come in: through-hole or surface mount.
The largest regulators are almost always in through-hole packages designed to provide amps of current. SMD regulators don’t provide more than an amp of current but are conveniently sized.
Linear regulators are used in conjunction with a DC converter, as linear regulators are not efficient when regulating large differences in voltage (such as 10V to 3.3V).
The DC converter reduces the voltage power close to the regulating voltage level, which is then fed into the linear regulator.
Through-Hole Linear Regulator
Through-hole parts are available in most common transistor packages, including TO-92, TO-220, and even TO-3.
The TO-92 packages are an older variety used when low currents are needed (they are now replaced with SMD regulators). The TO-220 packages are useful for currents up to 1.5A (currents beyond this require the TO-3 package, usually in older hardware).
Through-hole regulators are often connected to a heat sink, which can be a solid piece of metal, fins, or a fan.
SMD Linear Regulators
Surface mount regulators also come in a number of packages, among them include SOT-89, SOT-223, SOT-23, and TO252-3. SMD linear regulators can have as few as 3 pins but typically have between 4 and 6.
The extra pins are often used as additional inputs or outputs that enable a higher current operating alongside the SOT-223, which has considerable output.
Most modern electronics use LDO (low drop output). For example, mobiles take advantage of LDOs to improve efficiency.
DC Converters and SMPS Regulators
DC converters and switch mode power supply (SMPS) regulators are devices that use high frequency switching voltages to either reduce a voltage (buck converter) or increase it (boost converter).
These converters are not easily identified on their own as they often look like standard ICs (8-pin packages are the most common). However, it helps to identify them by their names, the components that surround them, and other tell-tale signs on a PCB.
DC converters can be named either U or IC and are always surrounded by resistors, capacitors, and at least one inductor.
SMD DC-DC converters are found in SOIC-8 packages, as well as packages as small as QFN.
Converters in properly designed products are often surrounded by stitching, which is used to tie two power planes together to create a Faraday shield (also known as a Faraday cage).
This prevents stray electromagnetic energy from escaping and causing interference in other devices which is a requirement by FCC and CE standards.
Through-hole DC converters are available but they are rare in low power products (most consumer devices) and are in block-like packages.