Whats the cost structure and the key functions of the proteciton circuit board?
There are two ICs on the protection circuit board: the protection IC and the switch IC. The protection IC costs about US$0.15~0.5. And the switch IC, usually consists of two MOS FETs, is about US$0.2~0.3. There are another 5~7 R & C. So, roughly 20% costs is on the proteciton IC, 30% costs on the switch, and 15% costs on the others, 20% costs on labor and testing, another 15% is for overhead and profit margin. The key functions include over-current (include short circuit) protection, over-charge protection (limit the max voltage to about 4.25V), and over-discharge (limit the min voltage to about 3.0V) protection. The size of the proteciton circuit board is usually around 150 square milimeters (about 30mm * 5mm).
