| 摘要 |
Power dissipation is reduced in a video DAC by providing a sleep mode in which DAC current sources are shut off during the blanking period in a manner that allows them to be rapidly turned back on at the end of sleep mode. In particular, a digital to analog converter includes current surces (M1, M2, M3) and current steering circuits (M11/M12; M21/M22; M31/M32). The current steering circuits include switches responsive to first and second control signals for steering the current into either a load or return path. A control circuit generates the first and second signals as logical combinations of a video data signal and a sleep signal. The sleep signal, when it is active, causes both switches of a steering pair to turn off, which in turn causes the current source to turn off. At the end of the sleep mode the current source is rapidly turned back on by turning on one of the switches. Performance of the video DAC is not affected, while power dissipation is substantially reduced, facilitating higher-level integration and compliance with Green PC standard. Reduced power dissipation permits use of inexpensive packaging, reducing manufacturing costs and increasing reliability. |
