Impedance adjusting circuit and impedance adjusting method for zero quotient calibration

An impedance adjusting circuit for zero quotient (ZQ) calibration, comprising:

• a reference resistor, coupled between a first sensing node and a low reference voltage;
• a first pull-up impedance generator, coupled to an external voltage, wherein the first pull-up impedance generator comprises a plurality of first pull-up impedance units for providing a first resistance value respectively in response to a first calibration signal;
• a controller, coupled to the first sensing node, configured to connect the first pull-up impedance generator to the first sensing node, and compare a first reference voltage and a sensing voltage on the first sensing node to generate the first calibration signal in a first ZQ calibrating operation;
• and
• a detection circuit, coupled to the first sensing node and the controller, configured to detect the sensing voltage,
• wherein when the sensing voltage is out of a first specification range in the first ZQ calibrating operation, the detection circuit notifies the controller to perform a first compensation operation on the first pull-up impedance generator, and modifies the first calibration signal to an adjusted first calibration signal,
• wherein an adjusting resolution of the first compensation operation is higher than an adjusting resolution of the first ZQ calibrating operation.