An Adaptive Subharmonic Pulse Injection Crystal Oscillator Achieving —40 ∘C to 125 ∘C Operation

Subharmonic pulse injection crystal oscillators enable sub-nW operation with less frequent energy injection at oscillation peaks and valleys. However, this poses stringent requirements on the injection accuracy, which affects operation power, jitter, and reliability. To ensure accurate valley and peak injection across a wide temperature at minimum overhead, this work proposes the zero-voltage detection (ZVD)-based closed-loop timing adaptation, unbalanced differential injection and oscillation DC stabilizing techniques for a single-supply 16th subharmonic pulse-injection-based crystal oscillator (XO). Fabricated in 22-nm FDSOI, the IC enables operation across the widest reported temperature range from $-40~^{\circ }$ C to $125~^{\circ }$ C, and achieves a 11 ppb Allan deviation floor while consuming 0.72 nW and 0.006 mm2.