Time-Controlled and FinFET Compatible Sub-Bandgap References Using Bulk-Diodes

• Published in: IEEE transactions on circuits and systems. II, Express briefs Express briefs, 2019-10, Vol.66 (10), p.1608-1612
• Main Authors: Eberlein, M., Pretl, H., Georgiev, Z.
• Format: Article
• Language: English
• Subjects: bulk-diode; Capacitors; Charge pumps; Circuit design; Differential amplifiers; Diodes; Energy gap; FinFET process; FinFETs; Junctions; Nwell junction; Photonic band gap; Resistors; reverse bandgap; Substrates; Switched-capacitor; Switches; Timing; voltage reference
• ISSN: 1549-7747; 1558-3791
• DOI: 10.1109/TCSII.2019.2929599

This brief presents an innovative technique for precise reference generation based on "digital-alike" operation. The bias of pn-junctions is defined trough pulse timings, while respective PTAT and CTAT signals are sampled from the voltage-decay of a capacitor. The greatly simple structures offer intrinsic supply robustness and use charge sharing or addition, to achieve large reverse-bandgap levels. Here, we employ the bulk-to-substrate diode of any baseline process combined with charge-pump function, instead of BJT devices. Two different circuit ideas were designed in 16-nm FinFET, with ultra-low power requirements. The first version achieves an untrimmed 3σ-accuracy of ±0.82%, realizing 235-mV reference output down to 0.85-V supply. A second IP carries lowest complexity using a single diode only: it consumes 21 nA at 1680 μm 2 active area, and provides larger levels of Vref ~370 mV at merely ±2.7 mV total spread from silicon data. Unlike prior art, the compact reverse bandgaps do not require typical analog structures, like resistors, matched biasing, or differential amplifiers.