Proper Handling of NC Pins
When designing electronic circuits, IC datasheets contain various pin information. Among them, one that often appears is the NC pin (No Connection pin). In many cases, NC pins are assumed not to require any electrical connection. However, if handled incorrectly, they may cause unexpected issues.
This article explains the basic concept of NC pins and the handling methods that require particular attention.
１．Basic Concept of NC Pins
Pins explicitly labeled as NC should, in principle, not be connected to any circuit electrically. This indicates that the pin is internally left open inside the IC.
Therefore, the correct handling is to leave it open (unconnected) without routing any wiring.
２．Similar Pin Names and Precautions
There are pins with similar names that may cause misunderstanding.
Even if they appear to be “unconnected” inside the IC, in reality, they may be internally tied to certain circuit blocks and require specific handling.
Pins internally connected but without functional use:
Some pins are marked as NC in the datasheet but are actually internally connected to certain circuit blocks. Although they have no direct function, they may require specific connections (e.g., to GND, VDD, or via a certain resistor) as specified in the datasheet to ensure stable operation or testing.
Failure to follow these instructions may result in malfunction, increased current consumption, noise generation, or even IC damage.
For Torex products, “NC pins” are consistently defined as pins that are not connected internally.
Pins that are internally connected but without function are given different pin names to help reduce design errors.
３．Principles of Proper NC Pin Handling
Based on the above, the most important principle when dealing with NC pins is:
“Even if a pin is labeled NC, always check the datasheet. If specific instructions are provided, strictly follow them.”
If the datasheet gives no specific instructions, leaving the pin open is acceptable. However, if there is any doubt, the safest approach is to consult the IC manufacturer.
For Torex products, NC pins are generally recommended to be left open.
However, for PCB layout purposes or compatibility with other ICs, NC pins may also be connected to other potential without causing problems.
Joined Torex Semiconductor in 2005.
After six years engaged in the development of power ICs such as DC/DC converters, worked for three years providing technical support for offline LED drivers.
Later took charge of technical support for Torex’s power IC customers.
With expertise gained through product development and extensive know-how accumulated from years of customer support — including solutions for power-related issues and troubleshooting — currently engaged in providing technical support and product proposals for Torex products.