| 摘要 |
A comparator used in an enhanced N-WELL pad voltage tracking circuit for high (5 Volts) voltage-tolerant buffers is designed to eliminate current leakage when the input/output is tristated and is being driven externally by a weak voltage source. This is accomplished by comparing the pad voltage supplied from the external source to a reference voltage that is a predetermined amount (VTP) less than the low internal voltage source (VDD). Thus, switchover for tracking of the N-WELL voltage tracks very closely the voltage VDD, reducing the differential voltage between the N-WELL and the pad on the pull-up driver for the system, thereby keeping the driver off and eliminating leakage current. The reference voltage is generated either by a diode voltage drop or by a weak source follower.
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