When someone get a new component, one of the first questions they often ask us is “what’s the pinout?”. If you’re lucky, the pinout and orientation for your device are clearly marked in the datasheet. However, if this is not the case, or if you are newer to electronics, this post will help you to understand what you are looking for.
Here is a basic rule that applies for most integrated circuits: There’s a polarity mark somewhere. From that polarity mark, move counterclockwise around the chip, and number the pins starting at 1.
Some suppliers use a polarity marker in the form of a half-moon shape at one end of the chip, like the 74HC9114D,112 from Nexperia, below.
This Nexperia device also shows another common Pin 1 indicator - an elongated bevel. Notice that the Pin 1 side of the chip is shown as having a longer bevel (‘bevel’ meaning the angled portion between the top face and the side wall of the plastic package) than the other side. When you see this bevel, Pin 1 is usually the lower-left pin,when the bevel is oriented downwards towards you.
Another is a small dot by pin 1, or sometimes a small triangle or tab instead. Sometimes several of these marks can appear, as in HCPL-181-000E from Broadcom, below. The larger black dot denotes pin 1 for HCPL-181-000E.
Often pin 1 is in a corner of the chip, and it’s only that corner — not the pin itself –that is marked by the small circle or triangle.