TP4056 is a popular lithium-ion battery charger IC (integrated circuit). It is commonly used in various electronic devices and DIY projects to charge single lithium-ion or lithium-polymer batteries. The TP4056 IC typically comes in a small form factor and provides features such as overcharge protection, over-discharge protection, and temperature regulation. It is widely used due to its low cost, efficiency, and ease of use, making it a popular choice for hobbyists and electronics enthusiasts.