Compensated oscillator circuit for charge pumps
View Patent ↗A charge pump oscillator circuit with compensation for variations in process and operating environment. The charge pump oscillator is designed with a rolloff characteristic that enables operation at both weak and strong process corners without excessive power consumption. Composite resistors in the oscillator circuit are composed of component resistors that are fabricated with different processes, e.g., implant and deposition. The resistance of the composite resistor is thus in order to provide compensation for variations in processing and operating environment. The composite resistor may be used as a feedback loop resistor, or may be used as a source degenerate resistor to control the supply current to the oscillator.
1. A charge pump circuit for a non-volatile memory integrated circuit comprising an oscillator circuit, wherein said oscillator circuit comprises a composite resistor to provide compensation for fabrication process variations and variations in an operational environment.
2. The charge pump circuit of claim 1 , wherein said oscillator circuit comprises at least one transistor coupled to a supply voltage (V cc ) by said composite resistor.
3. The charge pump circuit of claim 2 , wherein said composite resistor comprises a first resistor having a positive temperature coefficient of resistance and second resistor having a negative temperature coefficient of resistance.
4. The charge pump circuit of claim 2 , wherein said oscillator comprises a complementary transistor coupled to ground by said composite resistor.
5. The charge pump circuit of claim 2 , wherein the ratio between the value of the composite resistor to a value of an on resistance of said transistor increases with decreasing temperature over the temperature range of +100° C. to −40° C.
6. The charge pump circuit of claim 5 , wherein the ratio between the value of the composite resistor to a value of an on resistance of said transistor increases with decreasing temperature over the temperature range of +100° C. to +25° C.
7. The charge pump circuit of claim 2 , wherein said composite resistor comprises a first implanted resistor and a second deposited resistor.
8. The charge pump circuit of claim 7 , wherein said first resistor is an n-well resistor and said second resistor is a polysilicon resistor.
9. The charge pump circuit of claim 1 , wherein said oscillator circuit comprises a Schmitt trigger.
10. The charge pump circuit of claim 9 , wherein said oscillator circuit comprises a composite source degenerate resistor and a composite feedback loop resistor.
11. A flash memory device comprising:
an array of capacitors coupled by switches;
an oscillator circuit coupled to said array of capacitors, said oscillator circuit comprising a first resistor having a positive temperature coefficient of resistance, and a second resistor having a negative temperature coefficient of resistance.
12. The flash memory device of claim 11 , wherein said first resistor and said second resistor are connected in series.
13. The flash memory device of claim 12 wherein the net temperature coefficient of resistance is positive.
14. The flash memory device of claim 12 , wherein said first resistor and said second resistor are coupled to an input and an output of said oscillator circuit to provide a feedback current.
15. The flash memory device of claim 14 , wherein said implanted resistor is an n-well resistor.
16. The flash memory device of claim 15 , further comprising a feedback loop resistor and a source degenerate resistor.
17. The flash memory device of claim 14 , wherein said deposited resistor is a polysilicon resistor.
18. The flash memory device of claim 12 , wherein said oscillator circuit comprises a transistor coupled to one of said first resistor and said second resistor.
19. The flash memory device of claim 11 , wherein one of said first and second resistors is an implanted resistor and one of said first and second resistors is a deposited resistor.
20. The flash memory device of claim 11 , wherein said oscillator comprises a Schmitt trigger.