This is a square piece of metalization that is used for connecting a semiconductor chip to the outside world (wire bonding). Pads are usually located around the perimeter of a chip to allow easy wire bonding to a package; although when using the flipchip connection approach, pads may be located anywhere on the die. The term pad is also used to refer to the actual metal square and its surrounding circuitry, which frequently includes ESD protection and/or power output transistors. A typical ASIC will use several types of pads designed for specific purposes. These could be power, ground, analog input, analog output. digital output, etc.