The Tech Blog

Often called Trimpots, these little components are essential for fine-tuning circuits and ensuring your devices function just the way you want. A potentiometer is essentially a variable resistor, which allows you to manually adjust the resistance in a circuit. A trim pot is a type of potentiometer that’s designed for more precise, infrequent adjustments. Think of it as the control knob that you set once and forget. They are used for tuning circuits, setting reference voltages, and setting opamp gains when resistance tolerance needs to be handled post-assembly.

Trimpots have 3 terminals, two connected to the ends of a resistive element, and a third one (the wiper) that slides along the resistive track. By adjusting the wiper, you change the resistance between the wiper and each end of the resistor. What you need to remember is that there will always be a finite resistance between the terminals, it may not always be zero on one end. Refer to the datasheets for the minimum resistance or the terminal resistance for this value. When selecting trimpots, consider the same factors you’d consider when choosing a resistor like resistance tolerance, temperature variation, and power rating. What is extra would be contact variational resistance, which is the max change in contact resistance that will be encountered when the wiper moves from one place to another. We want this to be low. Good quality manufacturers also specify vibrational or shock tolerances.

They come in different shapes and types. The key one is a single turn vs multi-turn. It specifies the number of rotations you need to full resistance range. Multiturns are expensive but offer precise control of resistance for fine-tuning. It comes in open frame or sealed packages(useful in high humidity cases).

A common mistake I see among clients is using trimpots(as they are smaller) where rotary potentiometers should be used. Trimpots have a notoriously short lifespan (100-200 cycles) compared to rotary pots (about 10k cycles). Always check the datasheet for cycles! If the knob will be adjusted often, use a rotary pot.

This is one topic I wish someone had taught me when I first started designing boards. Back then, finding content online wasn’t as easy as it is today. Vias are essentially small holes that create electrical connections between different layers of a PCB. Whether a PCB has just 1 layer or several, vias are the key to connecting layers and routing signals between them.

The most common via is the Through-hole via, drilled from the top to the bottom layer, connecting one or more layers in between. It doesn’t need to connect all layers, but the hole goes completely through the PCB. It’s the cheapest option due to easy manufacturing (drill once through all layers). However, it takes up space, and you can’t place parts or pads on both sides unless you use a via-in-pad. If the signal doesn’t connect the top and bottom layers, the metallic hole can create stubs(We can discuss this in the future) that cause reflections in high-speed designs.

Blind Vias connect one outer layer to one or more inner layers but do not go all the way through the board. Useful when you want to save on space and can do part mounting on the other layer that you haven’t connected to.

Buried Vias as the name suggests, is buried inside the PCB, in the inner layers, with no direct connection to the 2 outer layers. Pros: Excellent for multi-layer PCBs, no impact on the outer layers, great for high-density designs. Both Buried and Blind vias are expensive as they require multiple stacking and drilling processes.

Micro vias are a special type of via with an aspect ratio of 1:1 or less and a hole depth of less than 0.25mm, typically used for single-layer transitions. Unlike traditional cylindrical vias, micro vias have a conical structure that tapers from one layer to the next. Categorized into two types: Stacked Vias, where multiple micro vias are aligned vertically across different layers (one on top of the other), and Staggered Vias, where vias are placed on different layers but do not align directly with each other.

Always weigh the trade-offs between cost and space requirements for your next PCB design.