Circuit and method of generating high voltage for programming operation of flash memory device
Provided is a high voltage generator for a flash memory device including a voltage pumping unit configured to generate a high voltage in response to a pumping clock signal, a transistor having a gate coupled to the high voltage and a source coupled to a program voltage, a voltage distributor coupled to the drain of the transistor, the voltage distributor configured to generate a distributor voltage, and a pumping clock controller configured to compare the distributor voltage to a reference voltage and to generate the pumping clock signal when the high voltage is less than a voltage substantially equal to the program voltage plus the threshold voltage of the transistor.
1. A high voltage generator for a flash memory device comprising:
a voltage pumping unit configured to generate a high voltage in response to a pumping clock signal;
a transistor having a gate coupled to the high voltage and a source coupled to a program voltage;
a voltage distributor coupled to the drain of the transistor, the voltage distributor configured to generate a distributor voltage; and
a pumping clock controller configured to compare the distributor voltage to a reference voltage and to generate the pumping clock signal when the high voltage is less than a voltage substantially equal to the program voltage plus the threshold voltage of the transistor.
2. The high voltage generator of claim 1 , wherein the transistor is a high voltage transistor.
3. The high voltage generator of claim 1 , wherein the voltage distributor is further configured to set the distributor voltage at a level substantially equal to the reference voltage when the voltage on the drain of the transistor is substantially equal to the program voltage.
4. The high voltage generator of claim 1 , wherein:
the transistor further comprises a feedback transistor; and
the voltage distributor further comprises:
a first resistor having one end coupled to the drain of the feedback transistor;
a distributor transistor having a source coupled to the other end of the first resistor, and a gate coupled to a power supply; and
a second resistor coupled between a drain of the distributor transistor and a ground.
5. The high voltage generator of claim 1 , wherein the pumping clock controller comprises:
a comparator configured to compare the distributor voltage to the reference voltage; and
a NAND gate configured to receive the output signal of the comparator, a control signal instructing the high voltage to be generated, and a clock signal, and configured to generate the pumping clock signal.
6. The high voltage generator of claim 1 , further comprising a high voltage discharging unit configured to discharge the high voltage to a power supply in response to an enable signal instructing the high voltage to be discharged.
7. The high voltage generator of claim 6 , wherein the high voltage discharging unit comprises:
a PMOS transistor having a source coupled to the power supply voltage and a gate coupled to the enable signal;
a first NMOS transistor having a source coupled to the drain of the PMOS transistor and a gate coupled to an inverted version of the enable signal; and
a second NMOS transistor having a source coupled to the drain of the first NMOS transistor, a gate coupled to the power supply voltage, and a drain coupled to the high voltage.
8. A high voltage generator for a flash memory device comprising:
a voltage pumping unit configured to generate a high voltage in response to a pumping clock signal;
a transistor having a gate coupled to the high voltage and a source coupled to a read voltage;
a voltage distributor coupled to the drain of the transistor, the voltage distributor configured to generate a distributor voltage; and
a pumping clock controller configured to compare the distributor voltage to a reference voltage and to generate the pumping clock signal when the high voltage is less than a voltage substantially equal to the program voltage plus the threshold voltage of the transistor.