an intelligent power MOSFET

Hitachi Ltd. (Ibaraki-ken, Japan) has developed an intelligent power MOSFET with built-in reverse battery protection. As reported in the IEEE Transactions on Electron Devices, the new device is called a RBPFET (Reverse Battery Protected FET) and is designed for use in automotive applications. The RBPFET is a drop-in replacement for conventional three-terminal power MOSFETs. Protection is accomplished by integrating an additional power MOSFET in series with the primary device. The positive drain breakdown voltage for the resulting device is 71V and the negative drain current at a drain voltage of -16V is -750 microAmps. The Rds(on) of the device is 170 milliohms. Reverse battery protection is achieved by sensing the negative drain voltage with an on-chip voltage comparator. As a result, the RBPFET operates without adding a protection diode, and can replace a conventional three-terminal power MOSFET without increasing board space. By employing two low on-resistance FETs, the total on-state resistance of the RBPFET can be reduced to less than that of a conventional power MOSFET with a protection diode. The circuit configuration using two n-channel power MOSFETs with a common drain is similar to that of bi-directional switches and similar circuits. While samples of these 3.2 mm-square devices have been fabricated, production plans have not been announced.