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US 7,889,018 B2Granted
Low VT dependency RC oscillator
AssigneeSanDisk Corporation
InventorTomer Shaul Elran
Life of this patent
Estimating the term…
Abstract
An oscillator utilizes two current sources that have the same temperature and VDD dependency so they generate the same current in changing conditions. Therefore, there is very low VT dependency. The resistor and fringe capacitor temperature coefficient are very low and opposite so they compensate for each other. A comparator with a short period of operation also minimizes VT dependency.
Claims9
An oscillator comprising:
- a first current source, the first current source characterized by:
- a first temperature dependency;
- a first input voltage dependency;
- a second current source, the second current source characterized by:
- a second temperature dependency;
- a second input voltage dependency;
- the first temperature dependency equal to the second temperature dependency, the first input voltage dependency equal to the second input voltage dependency;
- a reference voltage generated by applying a current of the first current source to a resistor;
- a capacitor coupled to an output of the second current source;
- and
- a comparator comprising an output and configured to change the output when the capacitor voltage reaches the reference voltage,
- wherein the change in resistance with temperature of the resistor is substantially equal in magnitude to the change in capacitance of the capacitor with temperature.
9 more elements
A method of providing a clock signal in a memory device, the method comprising:
- providing a first and a second current source, the first and second current source having the same VGS;
- applying a current of the first current source to a resistor and generating a reference voltage;
- applying a current of the second current source to a capacitor and charging the capacitor;
- and
- when the capacitor voltage reaches the reference voltage generating the clock signal
- wherein the change in resistance/change in temperature of the resistor to which the first current source is applied is substantially equal in magnitude to the change in capacitance/change in temperature of the capacitor to which the second current source is applied.
3 more elements
Dependencies are inferred from the claim text.