A 12-/13.56-MHz Crystal Oscillator With Binary-Search-Assisted Two-Step Injection Achieving 5.0-nJ Startup Energy and 45.8-s Startup Time

This article reports a 12-/13.56-MHz fast-and-energy-efficient startup crystal oscillator (XO) featuring a binary-search-assisted two-step injection technique for ultralow-power duty-cycled radios. Specifically, after the first injection, a calibration module refines the auxiliary oscillator's frequency toward the crystal's resonant frequency in a binary-search fashion with a sub-500-ppm error for the second injection. This calibration method eliminates the closed-loop phase-locked loop (PLL) and shortens the calibration period into 48 clock cycles. Prototyped in a 65-nm CMOS process, the XO occupies an active area of 0.134 mm(2). The 13.56-MHz XO can achieve a startup time (t(s)) of 45.8 mu s with a V-DD of 0.7 V, while consuming 5.0 nJ of energy. t(s) varies by +/- 2.2% amid temperature variations (-40 degrees C to 85 degrees C). Its steady-state power consumption is 28.4 mu W, with an output phase noise of -143.7 dBc/Hz at 1-kHz offset (FoM: 241.8 dBc/Hz), manifesting its state-of-the-art performance.