Memory system and method for measuring capacitance value

A memory system, comprising:

• a nonvolatile semiconductor memory;
• a capacitor configured to store charge to be supplied to the nonvolatile semiconductor memory;
• a constant current circuit configured to extract the charge from the capacitor at a constant current;
• and
• a controller configured to calculate a capacitance value of the capacitor and a resistance value of a leakage resistance through which a leakage current of the capacitor flows, based on:
• a terminal voltage of the capacitor;
• a first differential voltage and a first elapsed time in a first period during which a natural discharge measurement is performed;
• and
• a second differential voltage and a second elapsed time in a second period during which a constant current measurement is performed, wherein
• the terminal voltage is measured from a start of the natural discharge measurement until the terminal voltage drops by the first differential voltage and from a start of the constant current measurement until the terminal voltage drops by the second differential voltage, and
• the first elapsed time is measured from the start of the natural discharge measurement until the terminal voltage drops by the first differential voltage and the second elapsed time is measured from the start of the constant current measurement until the terminal voltage drops by the second differential voltage.

A method for measuring a capacitance value for a capacitor of a memory system, the method comprising:

• measuring terminal voltages of the capacitor in a first period during which the capacitor naturally discharges and a second period during which charge is extracted from the capacitor at a constant current;
• measuring a first time required for the terminal voltage to drop by a first amount from an initial value at a start of the first period;
• measuring a second time required for the terminal voltage to drop by a second amount from an initial value at a start of the second period;
• and
• calculating a capacitance value of the capacitor based on the measured first time, the measured second time, the first drop amount, and the second drop amount by using a formula including a resistance value of a leakage resistance through which a leakage current of the capacitor flows as a variable in each of the first period and the second period.