A hardware / firmware co-design solution in an 8-bits microcontroller has been proposed to practically fix the system-level ESD (electrostatic discharge) issue on the keyboard products. By including the especial ESD sensors and an additional ESD flag into the chip, the fast electrical transient due to the system-level ESD zapping on the keyboard can be detected. The firmware stored in the ROM of the 8-bits microcontroller is designed to automatically check the ESD flag to monitor the abnormal conditions in system operations. If the keyboard is upset or locked up by a system-level ESD transient, the microcontroller can be quickly recovered to a known and stable state. The 8-bits microcontroller with such a hardware / firmware co-design solution has been fabricated in a 0.45- mu m CMOS process. The system-level ESD susceptibility of the keyboard with this 8-bits microcontroller has been improved from the original 2kV (4kV) to become greater than 8kV (15kV) in the contact-discharge (air-discharge) ESD zapping.
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