Patent ID: 6262603
Filing Date: 2001-07-17
Classification: H03B,H03H

Abstract:
An RC calibration circuit comprising:a first current source that sources a first current into a first node;a second current source that sources a second current into a second node;a switch connected between the second node and ground, the switch having an open position and a closed position;a resistor connected between the first node and ground, the resistor generating a first voltage in response to the first current;a variable capacitor connected between the second node and ground, the capacitor having a plurality of capacitances, and selecting one of the capacitances in response to a control word, the capacitor forming a second voltage in response to the second current charging up the capacitor when the switch is in the open position, the second current linearly charging the capacitor;a strobed comparator which has a first input connected to the second node, a second input connected to the first node, and an output, the comparator comparing the first voltage to the second voltage in response to a strobe signal, and outputting an indication of whether the first voltage is greater than the second voltage; anda control logic block connected to the switch, the capacitor, and the comparator, the logic block controlling the opening and closing of the switch and the output of the strobe signal such that the comparator compares the first voltage to the second voltage after a predefined time has elapsed since the switch was placed in the open position.