发明名称 |
Analog multiplexer cell for mixed digital and analog signal inputs |
摘要 |
An input cell circuit for an integrated circuit for use in a mixed signal mode where an input pin may receive either digital or analog signals. The circuit solves the problem where several such pins are used in a mixed signal mode and share a common internal bus. Such input signals will cause erratic values on the common analog bus, if any given input pin is used as a digital input signal and the voltage on that input pin exceeds the supply voltage by the base-emitter voltage of the parasitic transistor in the P-channel transistor in a pass gate in the associated input cell. This problem is solved by adding a second P-channel transistor to the pass gate and also adding an N-channel transistor connected to a node between the two P-channel transistors, as well as adding an input resistor. The second N-channel transistor is on while the other three transistors are off and exhibits a drain/source on-resistance such that the lateral and vertical bipolar parasitic transistors formed by the second P-channel transistor will not turn on and there is no leakage current between the input of the cell and the output of the cell.
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申请公布号 |
US5635745(A) |
申请公布日期 |
1997.06.03 |
申请号 |
US19940302308 |
申请日期 |
1994.09.08 |
申请人 |
NATIONAL SEMICONDUCTOR CORPORATION |
发明人 |
HOELD, WOLFGANG K. |
分类号 |
H01L27/06;H01L27/088;H03K17/16;H03K17/687;H03K17/693;(IPC1-7):H01L29/76 |
主分类号 |
H01L27/06 |
代理机构 |
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代理人 |
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主权项 |
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地址 |
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