Bandgap voltage reference circuitry

Abstract

Bandgap voltage reference circuitry capable of operating at very low power supply voltages is disclosed. The current source for driving the core bandgap voltage reference is implemented with insulated gate field effect transistors (M12, M15) having low threshold voltages. Voltage clamp circuitry (M21, M22, M24) protects the transistors from power supply voltage variations rising above a predetermined clamp voltage. An output amplifier with output biasing circuitry having a circuit structure similar to that of the core bandgap voltage reference ensures that the bandgap reaches the intended steady state of operation.

Description

technical field [0001] The present invention relates to a bandgap voltage reference circuit, in particular to a bandgap voltage reference circuit capable of operating at a low supply voltage (eg, in the range of 1.5-5.5V). Background technique [0002] Many types of circuits and systems require reliable voltage references. In particular, such voltage references are often required to remain consistent over temperature. Perhaps the most common voltage reference circuits rely on the bandgap of silicon. Various forms of such circuits have been designed and implemented to generate a reference voltage of 1.2V, which is substantially constant over time. However, if the circuit is required to operate at a lower voltage, such as 1.5V, then the 1.2V bandgap voltage leaves only 0.3V headroom. Such a small voltage headroom is often not enough to keep the circuit working properly. [0003] Referring to Figure 1, when operating at such low supply voltages (where headroom becomes a sig...

AI Technical Summary

Problems solved by technology

Although it is possible to use bandgap adjustment to improve the bandgap accuracy, the result is that the circuit size will become larger and the test time will be increased due to the adjustment required

This circuit architecture also limits the maximum supply voltage (VDD) when utilizing low-voltage devices (e.g., 1.8V maximum VDS), since the PMOS devices M0, M2, M3, M4, M6, and M7 are exposed to almost the full VDD voltage level

Adding a voltage protection circuit in series with these devices will increase circuit complexity and limit operation at low VDD supply levels

Images