Body bias circuits and methods
An integrated circuit can include an operational section comprising a first body bias circuit coupled to drive first body regions to a first bias voltage in response to at least first bias values; a second body bias circuit coupled to drive second body regions to a second bias voltage in response to at least second bias values; a plurality of monitoring sections formed in a same substrate as the operational section, each configured to output a monitor value reflecting a different process variation effect on circuit performance.
1. An integrated circuit, comprising:
at least one power supply transistor having a source-drain path coupled between a first power supply node and an internal power supply node, and a body coupled to a receive at least a first body bias voltage;
a plurality of monitoring sections formed in a same substrate as the power supply transistor, each configured to output a monitor value reflecting at least one different process variation effect on circuit performance;
a combination logic section configured to generate at least a first bias value by weighting and combining the monitor values;
a first bias circuit configured to generate the first body bias voltage in response to the first bias value; and
a power mode multiplexer circuit configured to selectively apply the first body bias voltage, or a lower body bias voltage to the body of the power supply transistor, the lower body bias voltage having a smaller magnitude and same polarity as the first body bias voltage.
2. The integrated circuit of claim 1 , wherein:
at least one of the monitoring sections is a drive monitoring circuit, comprising
at least one transistor under test (TUT) having a source coupled to a first monitor power supply node, a gate coupled to receive a start indication, and a drain coupled to a monitor node,
at least one monitor capacitor, and
a timing circuit configured to generate a monitor value corresponding to a rate at which the TUT can transfer current between the monitor node and the first monitor power supply node.
3. The integrated circuit of claim 1 , further including:
a core section comprising a plurality of core transistors formed in core body regions coupled to receive the first body bias voltage; and
an offset circuit configured to generate the lower body bias voltage from the first body bias voltage.
4. The integrated circuit of claim 1 , further including:
a regulated section comprising a plurality of transistors having sources coupled to the internal power supply node; and
a low dropout regulator circuit, comprising
the power supply transistor, and
an amplifier having a first input coupled to receive a reference voltage, a second input coupled to the regulated section, and an output coupled to a gate of the power supply transistor.
5. The integrated circuit of claim 1 , wherein:
the at one power supply transistor comprises a deeply depleted channel transistor having a substantially undoped channel formed over highly doped screening region to provide a strong body coefficient.
6. The integrated circuit of claim 1 , further including:
the plurality of monitoring sections include
at least one n-type drive monitoring circuit that includes
at least one n-type transistor under test (TUT) coupled to a first a monitor node,
a first monitor capacitor coupled to the first monitor node, and
at least one p-type drive monitoring circuit that includes
at least one p-type TUT coupled to a second monitor node,
a second monitor capacitor coupled to the second monitor node, and
timing circuits configured to generate monitor values corresponding to rates at which the n-type TUT can transfer current between the first monitor node and a first monitor power supply node, and the p-type TUT can transfer current between the second monitor node and a second monitor power supply node.