Patent ID: 8278952

Claim:
A voltage adjusting circuit for adjusting the output voltages supplied by a plurality of voltage sources, comprising: a test control device selecting one of the voltage sources as a testing voltage source, outputting a selecting command for selecting the testing voltage source, and outputting a target voltage corresponding to the testing voltage source via a pad; a multiplexer coupled to the voltage sources, receiving an enablement signal, and outputting a voltage supplied by the testing voltage source as a testing voltage according to the enablement signal; a comparator receiving the testing voltage and the target voltage, comparing the voltage levels of the testing voltage and the target voltage, and outputting a comparison result accordingly; and a built-in self test (BIST) device receiving the selecting command, outputting the enablement signal for enabling the testing voltage source according to the selecting command, and adjusting the voltage supplied by the testing voltage source to a predetermined voltage according to the comparison result, wherein when the voltage supplied by the testing voltage source is adjusted to the predetermined voltage, the test control device selects another voltage source from the voltage sources as the testing voltage source, outputs another selecting command for selecting the testing voltage source, and outputs the target voltage corresponding to the testing voltage source via the pad.