A display device using a surface capacitive touch panel is proposed. Upon a normal mode, an external clock generator supports a clock source; meanwhile, an external clock generator, a signal generator, a current detector, a current-to-voltage converter, an analog-to-digital converter, a filter, an interface controller, a microprocessor, and the touch-position calculators are turned on. But under a power-down mode, the external clock generator, the analog-to-digital converter, filter, the interface controller, the microprocessor, and the touch-position calculators are turned off in order to reduce power consumption. Furthermore, the external clock generator is also turned off to minimize the power consumption.