Electrical Characteristic of Power MOSFET with Zener Diode for Battery Protection IC

A high power MOSFET switch based on a 0.35 μm CMOS process has been developed for the protection IC of arechargeable battery. In this process, a vertical double diffused MOS (VDMOS) using 3 μm-thick epi-taxy layer isintegrated with a Zener diode. The p-n+ Zener diode is fabricated on top of the VDMOS and used to protect theVDMOS from high voltage switching and electrostatic discharge voltage. A fully integrated digital circuit with powerdevices has also been developed for a rechargeable battery. The experiment indicates that both breakdown voltageand leakage current depend on the doping concentration of the Zener diode. The dependency of the breakdownvoltage on doping concentration is in a trade-off relationship with that of the leakage current. The breakdown voltageis obtained to exceed 14 V and the leakage current is controlled under 0.5 μA. The proposed integrated module withthe application of the power MOSFET indicates the high performance of the protection IC, where the overcharge delaytime and detection voltage are controlled within 1.1 s and 4.2 V, respectively.