Negative charge pump regulation
View Patent ↗A negative charge pump is responsive to a pump enable signal. A voltage controlled current source provides a current. A resistor is coupled between a node from the voltage controlled current source and a negative charge output from the negative charge pump. A capacitor is placed in parallel with the resistor. A comparator generates the pump enable signal to control the negative charge pump. The comparator is coupled to the resistor and the capacitor and measures an IR drop thereacross and compares this measurement against a reference threshold. A level of the pump enable signal can be variable by tuning an amount of resistance of the resistor or capacitor or adjusting the reference threshold. A memory can be driven by a method of the negative charge pump.
1. A negative charge pump having output level regulation, comprising:
a negative charge pump responsive to a pump enable signal for generating a negative voltage at an output;
a voltage controlled current source for providing a current at a node;
a resistor circuit operatively coupled between the node of the voltage controlled current source and the output of the negative charge pump;
a capacitance circuit in parallel with the resistor circuit; and
a comparator operatively coupled to the resistor circuit and the capacitor circuit to compare an IR drop across the resistor circuit and the capacitor circuit against a reference threshold and to generate the pump enable signal to control the negative charge pump.
2. A negative charge pump according to claim 1 , wherein the output of the negative charge pump is variable by adjusting the reference threshold used by the comparator.
3. A negative charge pump according to claim 1 , wherein a ripple of an output of the negative charge pump is variable by adjusting a capacitance of the capacitor circuit.
4. A negative charge pump according to claim 1 , the ripple and level of the output of the negative charge pump is variable by tuning an amount of resistance of the resistor circuit.
5. A negative charge pump according to claim 4 ,
wherein the resistor circuit comprises a resistor stack comprising a plurality of series resistors;
wherein the negative charge pump further comprises a plurality of switches, each of the switches is operatively coupled to a corresponding one of the series resistors and controlled to operate a selected combination of the series resistors in the resistor stack; and
wherein the comparator measures and compares against the IR drop across the selected combination of the series resistors in the resistor stack.
6. A negative charge pump according to claim 5 , wherein the voltage controlled current source comprises:
a reference resistor;
a voltage input; and
an amplifier operatively coupled at the node to the selected combination of the series resistors in the resistor stack and to the capacitor circuit and to the reference resistor for providing the current based on the predetermined voltage input.
7. A negative charge pump according to claim 1 , wherein the voltage controlled current source comprises:
a reference resistor;
a voltage input; and
an amplifier operatively coupled at the node to the reference resistor for providing the current based on the predetermined voltage input.
8. A negative charge pump according to claim 7 , wherein the voltage input is trimmable.
9. A circuit including the negative charge pump according to claim 1 and further comprising a memory having memory cells operatively coupled to the output from the negative charge pump to alter states of the memory cells using the negative voltage.
10. A circuit according to claim 9 , further comprising a variance setting unit operatively coupled to at least one of a group consisting of the resistor circuit, the capacitor circuit, and the reference threshold to control a size of a ripple on the negative voltage.
11. A method of pump regulating a negative charge pump output level, comprising the steps of:
(a) generating in a negative charge pump a negative voltage at an output responsive to a pump enable signal and providing the negative voltage to a first side of a resistor circuit and a capacitor circuit in parallel;
(b) providing a current to a node at a second side of the resistor circuit and the capacitor circuit in parallel; and
(c) comparing an IR drop across the resistor circuit against a reference threshold to generate the pump enable signal to control the negative voltage at the output corresponding to the first side.
12. A method of pump regulating a negative charge pump according to claim 11 , wherein said step (c) of generating the pump enable signal further comprises a substep of (c)(2) adjusting the reference threshold used by the comparing to vary a level of the negative voltage at the output of the negative charge pump.
13. A method of pump regulating a negative charge pump according to claim 11 , wherein said step (c) of generating the pump enable signal further comprises a substep of (c)(2) adjusting a capacitance of the capacitor circuit to vary a ripple of the level of the negative voltage on the output of the negative charge pump.
14. A method of pump regulating a negative charge pump according to claim 11 , wherein said step (c) of generating the pump enable signal further comprises a substep of (c)(2) tuning an amount of resistance of the resistor circuit to vary a ripple of the level of the negative voltage on the output of the negative charge pump.
15. A method of pump regulating a negative charge pump according to claim 14 , wherein the resistor circuit comprises a resistor stack comprising a plurality of series resistors;
wherein said step (c)(2) of tuning an amount of resistance of the resistor circuit to vary the ripple and level of an output of the negative charge pump comprises a substep of (c)(2)(i) operating a plurality of switches to select a combination of the series resistors in the resistor stack; and
wherein said step (c) of comparing comprises substep of (c)(3) measuring and comparing against the IR drop across the selected combination of the series resistors in the resistor stack.
16. A method of pump regulating a negative charge pump according to claim 15 , wherein said step (b) of providing a current comprises a substep of (a)(1) providing the current based on the predetermined voltage using an amplifier operatively coupled at the node to the selected combination of the series resistors in the resistor stack and the capacitor circuit and a reference resistor.
17. A method of pump regulating a negative charge pump according to claim 11 , wherein said step (b) of providing a current comprises a substep of (a)(1) providing the current based on the predetermined voltage and a reference resistor using an amplifier operatively coupled at the node to the resistor circuit and the capacitor circuit.
18. A method of pump regulating a negative charge pump according to claim 11 , further comprising a step of (d) updating states of a memory using the negative voltage.
19. A method of pump regulating a negative charge pump according to claim 18 , wherein said step (d) of updating states of the memory using the negative voltage comprises the substeps of:
(d)(1) erasing memory cells of the memory; and
(d)(2) programming memory cells of the memory.
20. A method of pump regulating a negative charge pump according to claim 11 , further comprising the step of (e) selecting a variance setting of at least one of the resistor circuit, the capacitor circuit or the reference threshold to control a size of a ripple on the negative voltage.