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A circuit technique to detect unexpected power conditions such as battery separation is presented. Abrupt power-off owing to unexpected power conditions may cause an abnormal display in mobile TFT-LCDs because an adequate power-off sequence cannot be performed. The proposed abrupt power-off detector (APD) recognises decay of supply voltage and generates a signal to perform a proper power-off sequence. As mobile TFT-LCD driver ICs are usually operated with dual power supply, the APD detects abrupt power-off for both of the power supplies. To demonstrate the feasibility of the APD, a test chip was designed and fabricated in a 30 V/4 μm 5 V/0.8 μm 2.5 V/0.25 μm triple-well CMOS process. Experimental results show that the proposed APD improves display quality by allowing a proper power-off sequence at all abrupt power-off conditions.
Date of Publication: 19 Jan. 2006