| 摘要 |
A USB 2.0 transceiver includes a legacy full speed and low speed (FS/LS) USB driver that includes multiple output stages. The multiple output stages are connected in parallel to an output terminal. By sequentially providing the USB data to the multiple output stages, the USB signal at the output terminal will transition between logic states in an incremental fashion as the multiple output stages sequentially switch their individual output states. Consequently, the rise/fall time for the legacy FS/LS USB driver is controlled not by the strength of the inverter transistors in the output stages, but rather by the number of stages and the time interval between application of the USB data to each stage. Therefore, by selecting an appropriate number of output stages and an appropriate timing interval, accurate control over full speed and low speed USB signal rise/fall times can be provided.
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