A Sub-1 V 890 nW Single-BJT-Based Temperature Sensor and Voltage Monitoring ADC for SoC Applications in 180 nm CMOS

This paper presents a dual-function circuit for system-on-chip (SoC) applications that integrates both a temperature sensor and a voltage-monitoring analog-to-digital converter (ADC) within a single architecture. Unlike conventional bipolar junction transistor (BJT) based sensor implementations, which require multiple precisely matched BJTs, operating voltages higher than 1 V, dedicated ADCs, and complex signal-conditioning networks, the proposed design employs a single BJT as the sole sensing element and a simple ΔΣ switched-capacitor modulator, thereby reducing both area and design complexity. Fabricated in a 180 nm CMOS process, the proposed circuit operates at 0.95 V, consumes 890 nW, and occupies 0.0087 mm². As a temperature sensor, it achieves an accuracy of ±1.8^◦C (3σ) over a range of -30^◦C to 120^◦C after one-point trimming at 30^◦C. As a voltage-monitoring ADC, it delivers an 11-bit resolution with ±0.046% accuracy over a 0 to 5 V input range. These characteristics make the proposed circuit highly suitable for real-time thermal and voltage monitoring in power- and area-constrained SoCs, Moreover, by combining both temperature and voltage monitoring ADC in a single compact architecture, the proposed design significantly reduces system costs and complexity.