Patent ID: 8471599

Claim:
An adjustable voltage comparing circuit, comprising: a high-threshold reference module, comprising: a first memory, used for buffering a high-threshold reference signal transmitted by a logic tester; a first digital-to-analog converter, used for generating the high-threshold reference voltage according to a voltage level indicated by the high-threshold reference signal; a first shift register; a first counter; and a first switch; wherein the first shift register is used to the high-threshold reference signal in performance of serial-to-parallel data transformation through the first switch and buffer of the high-threshold reference signal in the first memory, and the first counter is used for counting so as to record a buffering address of the buffered high-threshold reference signal on the first memory; a low-threshold reference module, comprising: a second memory, used for buffering a low-threshold reference signal transmitted from the logic tester; a second digital-to-analog converter, used for generating the low-threshold reference voltage according to a voltage level indicated by the low-threshold reference signal; a second shift register; a second counter; and a second switch; wherein the second shift register is used to the low-threshold reference signal in performance of serial-to-parallel data transformation through the second switch and buffer of the low-threshold reference signal in the second memory, and the second counter is used for counting so as to record a buffering address of the buffered low-threshold reference signal on the second memory; and a comparing module coupled between the high-threshold reference module and the low-threshold reference module for determining whether a voltage level of a signal under test is between voltage levels of the high-threshold reference voltage and the low-threshold reference voltage.