Method and apparatus for dual mode output buffer impedance compensation
    2.
    发明授权
    Method and apparatus for dual mode output buffer impedance compensation 有权
    用于双模输出缓冲器阻抗补偿的方法和装置

    公开(公告)号:US6166563A

    公开(公告)日:2000-12-26

    申请号:US299771

    申请日:1999-04-26

    CPC分类号: H03K19/018585 H03K19/0005

    摘要: A method and circuit for programming an output buffer having a first output driver for producing a first signaling level with a first programmable strength and a second output driver for producing a second signaling level with a second programmable strength. The method includes coupling a test resistor between a source of the second signaling level and a mode terminal, sensing a first level at the mode terminal, and uncoupling the test resistor from the mode terminal. If the first level is between the second signaling level and a reference level, then programming the output buffer with reference to an unterminated transmission line coupled to the mode terminal. Otherwise, programming the output buffer with reference to an external resistor coupled between a source of the first signaling level and the mode terminal. The circuit includes a first counter coupled to the first comparator to produce a first value responsive to the mode flag, the mode terminal, and the reference level. A first latch, coupled to the first counter, provides the adjusted first value to the first output driver. A second latch, coupled to the second counter, provides the adjusted second value to the second output driver.

    摘要翻译: 一种用于编程具有第一输出驱动器的输出缓冲器的方法和电路,所述第一输出驱动器用于产生具有第一可编程强度的第一信号电平和用于产生具有第二可编程强度的第二信号电平的第二输出驱动 该方法包括将测试电阻器耦合在第二信号电平的源极和模式端子之间,感测模式端子处的第一电平,以及将测试电阻器与模式端子解耦。 如果第一级在第二信令电平和参考电平之间,则参考耦合到模式终端的未终端传输线来编程输出缓冲器。 否则,参考耦合在第一信号电平的源与模式终端之间的外部电阻来编程输出缓冲器。 电路包括耦合到第一比较器的第一计数器,以响应于模式标志,模式端子和参考电平产生第一值。 耦合到第一计数器的第一锁存器将经调整的第一值提供给第一输出驱动器。 耦合到第二计数器的第二锁存器向第二输出驱动器提供经调整的第二值。