Methods and apparatuses for dynamic step size for impedance calibration of a semiconductor device

1. An apparatus comprising:

a resistor; and

a chip comprising a driver impedance calibration circuit configured to determine an impedance of a driver based on an impedance of the resistor, wherein, during a calibration operation, the driver impedance calibration circuit is configured to adjust an impedance code that controls an impedance of the driver and to provide a next impedance code based on a comparison of a driver output voltage with a reference voltage, wherein an adjustment step size of the impedance code is determined based on a value of the impedance code, wherein the driver impedance calibration circuit comprises an adder/subtractor circuit configured to adjust the impedance code based on a comparison of a driver output voltage with a reference voltage and wherein the adder/subtractor circuit is configured to adjust the impedance code by a value equal to a value of a subset of most significant bits of the impedance code.

2. The apparatus of claim 1 , wherein the adder/subtractor circuit is configured to adjust the impedance code by a value equal to a value of three most significant bits of the impedance code.

3. The apparatus of claim 1 , wherein the adder/subtractor circuit is configured to adjust the impedance code by at least a value of 1.

4. An apparatus comprising:

a resistor; and

a chip comprising a driver impedance calibration circuit configured to determine an impedance of a driver based on an impedance of the resistor, wherein, during a calibration operation, the driver impedance calibration circuit is configured to adjust an impedance code that controls an impedance of the driver and to provide a next impedance code based on a comparison of a driver output voltage with a reference voltage, wherein an adjustment step size of the impedance code is determined based on a value of the impedance code, wherein the driver impedance calibration circuit comprises an adder/subtractor circuit configured to adjust the impedance code based on a comparison of a driver output voltage with a reference voltage and wherein the adder/subtractor circuit comprises a plurality of full adder circuits configured to perform a bitwise addition or subtraction operation based on the value of the impedance code to provide the next impedance code.

5. The apparatus of claim 4 , wherein the adder/subtractor circuit is further configured to limit a value of the impedance code a maximum value based on a count of bits included in the next impedance code.

6. A driver impedance calibration circuit of a semiconductor chip comprising:

an adder/subtractor circuit configured to, during an impedance calibration operation, adjust an impedance code to a next impedance code by a step size determined based on a value of the impedance code, wherein the adder/subtractor circuit is configured to adjust the impedance code by a value equal to a value of a subset of most significant bits of the impedance code.

7. The driver impedance calibration circuit of the semiconductor chip of claim 6 , wherein the adder/subtractor circuit is configured to set a minimum step size to 1.

8. A driver impedance calibration circuit of a semiconductor chip comprising:

an adder/subtractor circuit configured to, during an impedance calibration operation, adjust an impedance code to a next impedance code by a step size determined based on a value of the impedance code, wherein the adder/subtractor circuit is configured to adjust the impedance code by a value equal to a value of at least three most significant bits of the impedance code.

9. A driver impedance calibration circuit of a semiconductor chip comprising:

an adder/subtractor circuit configured to, during an impedance calibration operation, adjust an impedance code to a next impedance code by a step size determined based on a value of the impedance code, wherein the adder/subtractor circuit included a NAND logic gate to perform a bitwise NAND operation on a subset of inverted most significant bit values of the impedance code and a multiplexer configured to set the step size to the minimum step size based on an output of the NAND gate.

10. A driver impedance calibration circuit of a semiconductor chip comprising:

an adder/subtractor circuit configured to, during an impedance calibration operation, adjust an impedance code to a next impedance code by a step size determined based on a value of the impedance code, wherein the adder/subtractor circuit comprises a plurality of full adder circuits configured to perform a bitwise addition or subtraction operation based on the value of the impedance code to provide the next impedance code.

11. A method comprising:

receiving a command to adjust an impedance code that controls an impedance of a driver of a semiconductor chip;

determining a step size for adjustment of the impedance code based on a current value of the impedance code, wherein determining the step size for adjustment of the impedance code comprises setting the step size to a value of a subset of most significant bits of the current value of the impedance code; and

adjusting a value of the impedance code by the determined step size.

12. The method of claim 11 , wherein determining the step size for adjustment of the impedance code comprises setting the step size to a value of a three most significant bits of the current value of the impedance code.

13. The method of claim 11 , wherein determining the step size for adjustment of the impedance code comprises setting the step size to a minimum value when the current value of the impedance code less than a particular value.

14. The method of claim 11 , further comprising stopping adjustment of the impedance code when an impedance of the driver results in a desired output voltage.

15. The method of claim 11 , wherein adjusting the value of the impedance code by the determined step size comprises performing one of an addition or subtraction operation.

16. The method of claim 11 , further comprising comparing an output voltage of the driver with a reference voltage to determine whether to adjust the impedance code.