Feedback-controlled body-bias voltage source
View Patent ↗A body-bias voltage source having an output monitor, charge pump, and shunt. a shunt circuit having on/off control is coupled to the output monitor and to the output of the charge pump. Upon sensing that the output voltage of the charge pump is above a desired value, the output monitor may disable the charge pump circuit and may enable the shunt circuit to reduce the voltage at the output of the charge pump. When the voltage output of the charge pump is below the desired value, the output monitor may disable the shunt circuit and may enable the charge pump circuit. A shunt circuit having proportional control may be substituted for the shunt circuit with on/off control.
1. A system comprising:
first circuitry operable for generating an output voltage;
second circuitry coupled to said first circuitry and operable for adjusting said output voltage in response to a control signal by providing a discharge path for said output voltage if enabled; and
an output monitor coupled to said first circuitry and operable for comparing said output voltage and a reference voltage and operable for generating said control signal based on a result of said comparing, wherein said control signal has a state that is proportional to an amount of difference between said output voltage and said reference voltage, wherein said output monitor is further operable for enabling said first circuitry in response to sensing an undervoltage condition, and wherein further an amount of voltage discharged via said second circuitry is configured to be proportionally controlled according to said state of said control signal.
2. The system of claim 1 wherein said first circuitry comprises a charge pump.
3. The system of claim 1 wherein said second circuitry comprises a shunt circuit.
4. The system of claim 1 wherein an effective resistance of said second circuitry, if enabled, is configured to be proportionally controlled according to said state of said control signal.
5. The system of claim 1 wherein said output monitor is further operable for enabling said second circuitry to provide said discharge path for said output voltage in response to sensing an overvoltage condition.
6. The system of claim 1 wherein said output monitor is further operable for disabling said second circuitry in response to sensing said undervoltage condition.
7. The system of claim 1 wherein said output monitor is further operable for cycling said second circuitry between enabled and disabled states in response to sensing an undervoltage condition if said first circuitry is enabled.
8. The system of claim 1 wherein said first circuitry is coupled to a P-type well, and wherein said output voltage comprises a negative voltage usable as a body bias voltage to bias said P-type well.
9. The system of claim 1 wherein said first circuitry is coupled to an N-type well, and wherein said output voltage comprises a positive voltage usable as a body bias voltage to bias said N-type well.
10. The system of claim 1 further comprising a current source coupled to a variable resistor, wherein said current source and said variable resistor are operable for providing said reference voltage.
11. A device comprising:
a well disposed in a substrate;
first circuitry operable for generating a body bias voltage for biasing said well;
an output monitor coupled to said first circuitry and operable for comparing said body bias voltage and a reference voltage and operable for generating a control signal based on a result of said comparing, wherein said control signal is proportional to an amount of difference between said output voltage and said reference voltage; and
second circuitry coupled to said first circuitry and operable for adjusting said body bias voltage in response to said control signal, wherein said output monitor is further operable for enabling said first circuitry in response to sensing an undervoltage condition, and wherein further an amount of voltage discharged via said second circuitry is configured to be proportionally controlled according to said state of said control signal.
12. The device of claim 11 wherein said first circuitry comprises a charge pump and said second circuitry comprises a shunt circuit.
13. The device of claim 11 wherein said output monitor is further operable for enabling said second circuitry to provide a discharge path for said body bias voltage in response to sensing an overvoltage condition.
14. The device of claim 11 wherein said output monitor is further operable for disabling said second circuitry in response to sensing said undervoltage condition.
15. The device of claim 11 wherein said output monitor is further operable for cycling said second circuitry between an enabled state and a disabled state in response to sensing an undervoltage condition if said first circuitry is enabled, and wherein said second circuitry, if enabled, provides a discharge path for said body bias voltage.
16. A method comprising:
sensing a first voltage at an output monitor coupled to an integrated circuit;
sensing a reference second voltage at said output monitor;
generating a control signal based on a comparison of said first voltage and said second voltage, wherein said control signal has a state that is proportional to an amount of difference between said first voltage and said second voltage; and
adjusting said first voltage in response to said control signal via a discharge path that shunts said first voltage if enabled; and
enabling a source of said first voltage in response to sensing an undervoltage condition, and wherein further an amount of voltage discharged via said second circuitry is configured to be proportionally controlled according to said state of said control signal.
17. The method of claim 16 further comprising:
enabling said discharge path for said first voltage in response to sensing an overvoltage condition; and
varying an effective resistance of said discharge path according to said state of said control signal.
18. The method of claim 16 further comprising disabling said discharge path for said first voltage in response to sensing an undervoltage condition.
19. The method of claim 16 further comprising cycling said discharge path for said first voltage between an enabled state and a disabled state in response to sensing an undervoltage condition if a source of said first voltage is enabled, and wherein, in said enabled state, an effective resistance of said discharge path is varied according to said state of said control signal.
20. The method of claim 16 wherein said first voltage comprises a negative voltage usable as a body bias voltage to bias a P-type well of said integrated circuit.
21. The method of claim 16 wherein said first voltage comprises a positive voltage usable as a body bias voltage to bias an N-type well of said integrated circuit.