Voltage generator, nonvolatile memory device comprising voltage generator, and method of operating voltage generator

1. A voltage generator, comprising:

a first booster that generates a first high voltage; and

a second booster that generates a second high voltage by boosting an external voltage,

wherein the first booster comprises a comparator that controls a boosting operation with reference to a fed back version of the first high voltage and uses the second high voltage as a drive voltage.

2. The voltage generator of claim 1 , wherein the first booster comprises a voltage divider that adjusts a level of the first high voltage to provide it as a feedback voltage.

3. The voltage generator of claim 2 , wherein the feedback voltage is higher than the external voltage.

4. The voltage generator of claim 2 , wherein the first booster comprises a charge pump that boosts the second high voltage to the first high voltage under control of the comparator.

5. The voltage generator of claim 1 , wherein the first booster comprises a reference voltage generator that generates a reference voltage, and a trim circuit that trims the reference voltage to provide it as a reference input of the comparator.

6. A nonvolatile memory device comprising:

a memory cell array;

a write driver that writes data in the memory cell array;

a sense amplifier that reads data written in the memory cell array; and

a voltage generator that provides a first high voltage to the write driver and a second high voltage to the sense amplifier,

wherein the voltage generator comprises a comparator that controls a boosting operation with reference to a fed back version of the first high voltage and uses the second high voltage as a drive voltage.

7. The nonvolatile memory device of claim 6 , wherein the voltage generator comprises:

a first booster that generates the first high voltage;

a second booster that generates the second high voltage by boosting an external voltage.

8. The nonvolatile memory device of claim 7 , wherein the first booster comprises a voltage divider that adjusts a level of the first high voltage to provide the first high voltage as a feedback voltage.

9. The nonvolatile memory device of claim 8 , wherein the feedback voltage is higher than the external voltage.

10. The nonvolatile memory device of claim 7 , wherein the first booster comprises a charge pump that boosts the second high voltage to the first high voltage under control of the comparator.

11. The nonvolatile memory device of claim 7 , wherein the first booster comprises:

a reference voltage generator that generates a reference voltage; and

a trim circuit that trims the reference voltage and provides it to the comparator.

12. The nonvolatile memory device of claim 6 , wherein the second high voltage is activated in a read operation mode, a standby mode, or a write operation mode.

13. A method of operating a voltage generator, comprising:

operating a first booster to generate a first high voltage;

operating a second booster to generate a second high voltage by boosting an external voltage; and

controlling a boosting operation of the first booster using a comparator that compares a fed back version of the first boosting voltage with a reference voltage and uses the second high voltage as a drive voltage.

14. The method of claim 13 , wherein the first booster comprises a voltage divider that adjusts a level of the first high voltage to provide the first high voltage as a feedback voltage.

15. The method of claim 14 , wherein the feedback voltage is higher than the external voltage.

16. The method of claim 13 , wherein the first booster comprises a charge pump that boosts the second high voltage to the first high voltage under control of the comparator.

17. The method of claim 13 , wherein the first booster comprises a reference voltage generator that generates the reference voltage, and a trim circuit that trims the reference voltage and provides it to the comparator.