Well bias voltage generator
View Patent ↗A well bias module outputs a voltage used to bias the wells of transistors or other semiconductor components. The well bias module includes a feedback loop having a voltage generation module and a subthreshold leakage sense module that is operable to model the transistors or other semiconductor components so as to sense the subthreshold leakage resulting from a particular well bias voltage output by the voltage generation module. The subthreshold leakage sense module provides a representation of the sensed subthreshold leakage to the voltage generation module, which adjusts the magnitude of the well bias voltage based on this representation so as to reduce or minimize the subthreshold leakage in the transistors or other semiconductor components.
1. An apparatus comprising:
a first transistor formed at a first well region, the first transistor comprising a first current electrode, a second current electrode coupled to the first well region, and a control node, wherein the first well region is of a first conductivity type;
a second transistor formed at a second well region that is different than the first well region, the second transistor comprising a first current electrode, a second current electrode coupled to the second current electrode of the first transistor, and a control node coupled to the control node of the first transistor, wherein the second well region is of the first conductivity type;
a current mirror comprising a first node coupled to the first current electrode of the first transistor and a second node coupled to the first current electrode of the second transistor, wherein a first current is to be provided by the current mirror at the first node and a second current is to be provided by the current mirror at the second node such that a ratio of the first current to the second current is predetermined; and
a voltage generator comprising an input coupled to the first current electrode of the second transistor and an output coupled to the second well region to provide a well bias voltage based upon a signal value at the input.
2. The apparatus of claim 1 , further comprising:
a current source comprising a first node and a second node coupled to the control electrode of the first transistor.
3. The apparatus of claim 2 , further comprising:
a third transistor comprising a first current electrode coupled to the control electrode of the first transistor, a second current electrode coupled to the second current electrode of the second transistor, and a control electrode coupled to the first current electrode.
4. The apparatus of claim 3 , further comprising:
a resistive element in series between the well region of the second transistor and the output of the voltage generator.
5. The apparatus of claim 3 , wherein the third transistor is at a third well region that is different than the second well region.
6. The apparatus of claim 5 , wherein the third well region is the same as the first region.
7. The apparatus of claim 5 , wherein a well region of the third transistor is a different well region than the first transistor.
8. The apparatus of claim 1 , further comprising:
a resistive element in series between the well region of the second transistor and the output of the voltage generator.
9. The apparatus of claim 1 , further comprising:
a third transistor comprising a first current electrode coupled to the control electrode of the first transistor, a second current electrode coupled to the second current electrode of the second transistor, and a control electrode coupled to the first current electrode.
10. The apparatus of claim 1 wherein a gate width of the second transistor is greater than a gate length of the first transistor.
11. The apparatus of claim 1 wherein a gate width of the second transistor is greater than twice the gate length of the first transistor.
12. A method comprising:
providing a well bias voltage to a well region;
biasing a device based upon the well bias voltage; and
modifying the well bias voltage provided to the well region to compensate for sub-threshold leakage variations over a range of process variations and a range of temperature variations.
13. The apparatus of claim 12 , wherein modifying the well bias voltage comprises providing an indication of the sub-threshold leakage to a signal controlled oscillator.
14. An apparatus comprising:
a well bias voltage sense module comprising an input and an output, the well bias voltage sense module to sense an input signal and provide a control signal at the output based upon a relationship between the input signal and a desired signal;
a device leakage sense module comprising an input coupled to the input of the voltage sense module and an output, the device leakage sense module to sense a leakage current of a device and provide a control signal at the output based upon a magnitude of the leakage current;
a select module comprising a first input coupled to the output of the well bias voltage sense module, a second input coupled to the output of the device leakage sense module, and an output to provide a representation of one of a first signal received at the first input or a second signal received at the second input; and
a signal generator comprising an input coupled to the output of the select module, and an output coupled to the input of the voltage sense module.
15. The apparatus of claim 14 , wherein the select module further comprises
a first transistor formed at a first well region, the first transistor comprising a first current electrode, a second current electrode coupled to the first well region, and a control node, wherein the first well region is of a first conductivity type;
a second transistor formed at a second well region that is different than the first well region, the second transistor comprising a first current electrode, a second current electrode coupled to the second current electrode of the first transistor, and a control node coupled to the control node of the first transistor, wherein the second well region is of the first conductivity type; and
a current mirror comprising a first node coupled to the first current electrode of the first transistor, and a second node coupled to the first current electrode of the second transistor, wherein a first current is to be provided by the current mirror at the first node and a second current is to be provided by the current mirror at the second node such that a ratio of the first current to the second current is predetermined.
16. A method comprising:
determining a first leakage current for at least a portion of an apparatus in response to the at least a portion of the apparatus comprising a first well bias voltage;
determining a desired leakage current for the at least a portion of the apparatus; and
defining a ratio of a first transistor width to a second transistor width to be approximately equal to the ratio of the first leakage current to the desired leakage current.
17. The apparatus of claim 16 , wherein determining the first leakage and determining the desired leakage is determined when the at least a portion of the apparatus is in a low-power mode of operation.