Internal Bandgap Voltage Error Reduction in High Gradient Layouts
Internal bandgap voltage errors in high gradient layouts are reduced by common-centroid matching, thermal isolation trenching, and package stress mitigation.
Proportional to Absolute Temperature
Thermal Generation
Electronic current or voltage sources produce an output signal that increases linearly with thermodynamic temperature. This proportional to absolute temperature output is widely used as a thermal sensing element and as a core building block in bandgap voltage references.
Transistor Mechanism
The difference in base-emitter voltages between two bipolar transistors operating at different current densities generates this linear relationship. The resulting differential voltage is directly proportional to the absolute temperature in kelvins, scaled by the ratio of the junction areas and the physical constants of silicon. This signal is amplified to provide a usable analog output.
Sensor Integration
Integrating these generators into mixed-signal microchips enables highly accurate on-chip temperature measurement. The linear output is digitized by an analog-to-digital converter and processed to display temperature in standard units. Because the raw signal is small, the amplification stages must be designed with low-offset operational amplifiers to avoid corrupting the thermal reading.
Chopper stabilization is often used in these amplifiers to eliminate low-frequency noise and offset drift.
Metrological Tracking
Calibration is performed by comparing the sensor reading against a traceable external thermometer in a controlled liquid bath or dry block calibrator. The calibration coefficients are calculated and programmed into on-chip registers. This ensures the output remains accurate within a fraction of a degree.