Datasheets Glossary

Intro

In every inventor’s life, there comes a day when you order incompatible components. Logic levels don’t match, the hole on your PCB has the wrong dimensions, or there’s no library to handle the hardware (that one’s my nemesis). So, what can you do? How can you ensure that, during the design process, every component fits together nicely?

I believe it all starts with reading datasheets. If you could easily extract the most important information from a datasheet, your chances of making mistakes would drop significantly.

This article aims to describe common acronyms and terms used in electronic datasheets. No more fights between components—soon all your chips will work together like one big happy family.

Datasheet Sections

AMR – Absolute Maximum Ratings:
These are the values which, if exceeded, will damage your electronic component. This section usually lists voltage limits that must never be surpassed. These are not target operating values—just the maximums.

EC – Electrical Characteristics:
This section contains all the detailed specifications of a component’s electrical behavior. If all else fails, this is the section to turn to.

ROC – Recommended Operating Conditions:
These are the values you should supply to the device. Not maximums, but ideal ranges where the device is tested to work reliably. This is probably the most important section for designers.

Datasheet Terms and Acronyms (Alphabetically Sorted)

ADC – Analog-to-Digital Converter:
This chip converts analog voltage readings into binary values.

COM - Common: Usually used in relays or switches context. This pin is always connected to the switching device. Usually you connect device you want to controll to NC/NO and COM.

DIP – Dual In-Line Package:
A common chip package with pins on both sides. For example, 8-DIP has 8 pins. DIP chips are breadboard-friendly and popular for prototyping.

EC – See "Electrical Characteristics" under Datasheet Sections.

External Pull-down:
The component requires an external resistor to bring the pin voltage low. Be sure to add this resistor in your design.

External Pull-up:
The component requires an external resistor to bring the pin voltage high. Without it, the pin may float unpredictably.

GND / VSS – Ground Reference:
This is your reference point for voltage—usually the lowest voltage in the system. It doesn’t have to be 0 V unless stated in the datasheet. For example, VIM = 7 V and GND = 2 V still gives a 5 V difference.

GPIO – General-Purpose Input/Output:
These are versatile pins that can be configured as input or output. Common on microcontrollers.

H-Bridge – Full Bridge Driver:
A circuit made from four transistors that lets you drive a load (like a DC motor) in both directions. Common in motor driver datasheets.

I²C – Inter-Integrated Circuit:
Pronounced “I-squared-C.” A two-wire synchronous serial bus used for communication between chips. Wires: SDA (data), SCL (clock).

IN – Input Pin:
Used to control a component by applying voltage. Often numbered: IN0, IN1, etc.

Internal Pull-down:
The component has an internal resistor pulling the pin voltage low. No need for external resistors—just plug and play.

Internal Pull-up:
The component has an internal resistor pulling the pin voltage high. External resistors not needed.

I/O – Input/Output:
General term for signals or pins that can be either inputs or outputs. For example: “5 V tolerant I/O.”

LSB – Least Significant Bit:
The bit representing the smallest value in a binary number. In ADCs, it reflects the smallest voltage step. “LSB first” means data is sent starting with this bit.

MSB – Most Significant Bit:
The bit with the highest value in a binary number. For example, bit 7 in an 8-bit byte. Often used in communication and data formatting.

NC – No Connect:
Pin that is not connected internally. Leave it unconnected in your design.

NC – Normally Closed:
Usually used in relay context. By default this pin is connected to common pin, hence closed.

NO – Normally Open:
Usually used in relay context. By default this pin is not connected to common pin, hence open.

NRND – Not Recommended for New Designs:
Appears on older parts still in production but not advised for new designs. Usually because a better or more current alternative exists.

OUT – Output Pin:
Use this pin to read data or signals from a component. Often numbered: OUT0, OUT1, etc.

PWM – Pulse-Width Modulation:
A method for controlling power by rapidly switching voltage on and off. The “duty cycle” determines how much power is delivered—great for dimming LEDs or controlling motors.

REF – Voltage Reference:
Used with ADCs to set their full-scale range. For example, a 5 V reference on an 8-bit ADC gives 5/255 V per step.

ROC – See "Recommended Operating Conditions" under Datasheet Sections.

RX – Receive:
Common in UART contexts. Paired with TX (transmit). Look for RXD labels on datasheets.

SCL – Serial Clock (I²C):
Clock line used in I²C communication. Controlled by the master device.

SDA – Serial Data (I²C):
Bi-directional data line in I²C communication.

SMD – Surface-Mount Device:
A type of package designed to sit on the surface of a PCB. Common formats: QFP, QFN, BGA. Not meant for breadboards.

SPI – Serial Peripheral Interface:
A four-wire synchronous bus: SCLK (clock), MOSI (master-out, slave-in), MISO (master-in, slave-out), and SS (slave select). Used for fast communication with devices like displays or memory.

TX – Transmit:
In serial communication, the TX pin sends data out.

UART – Universal Asynchronous Receiver/Transmitter:
A hardware module for serial communication. Unlike SPI/I²C, it doesn’t use a clock line. Common in consoles and debug ports.

VCC – Positive Supply Voltage:
Originally “Voltage at Collector” (for BJTs), now widely used to refer to the positive voltage rail in digital circuits.

VDD – Voltage at Drain:
Supply voltage for MOSFET-based or CMOS-based devices (e.g., microcontrollers). Often used interchangeably with VCC.

VIL, VIH – Input Logic Levels:
- VIL: Max voltage to be read as LOW.
- VIH: Min voltage to be read as HIGH.
For example, in 3.3 V logic: VIL < ~1.0 V, VIH > ~2.3 V.

VSS – See "GND" or “Ground Reference.”

Summary

This glossary is a work in progress, and I’ll continue updating it as I explore new components and datasheets.

In this article, we unpacked a wide range of common terms and acronyms used in electronic datasheets. I hope this helps you better understand and “decrypt” technical documents, making your components happier working together.