| 摘要 |
PURPOSE: An output driver circuit is provided to suppress a transient current at a high supply voltage by adjusting the number of output driver transistors selectively turned on or off according to a level of the supply voltage. CONSTITUTION: The output driver circuit includes a supply voltage level detector(21), an output driver block(22) and an input/output pad(23). The supply voltage level detector outputs a plurality of pull-up signals(PU1-PUm) and a plurality of pull-down signals(PD1-PDm), detects a level of an external supply voltage in response to a pull-up signal(PU) and a pull-down signal(PD), and selectively activates the pull-up signals and pull-down signals according to the level of the external supply voltage. The output driver block has a plurality of PMOS transistors(MP1-MPm) receiving the pull-up signals on their gates, and a plurality of NMOS transistors(MNm) receiving the pull-down signals on their gates. The PMOS transistors and the NMOS transistors are driver transistors. The number of driver transistors enabled is determined by the number of the pull-up and pull-down signals activated. The input/output pad connects the output driver block with an external device(24).
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