During start-up, noise will be amplified in the inverting amplifier. The crystal will act as a bandpass filter and feed back only the crystal resonance frequency component, which will be amplified. Before steady state oscillation is achieved, the loop gain of the crystal/inverting amplifier loop is greater than 1 and the signal amplitude will increase. At steady state, the loop gain will fulfill the Barkhausen criteria with a loop gain of 1 and constant amplitude.
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High-ESR crystals will start more slowly than low-ESR crystals
High Q-factor crystals will start more slowly than low Q-factor crystals
High load capacitance will increase start-up time
Oscillator amplifier drive capabilities (see more details on oscillator allowance in Section 3.2, Negative Resistance Test and Safety Factor).
In addition, crystal frequency will affect the start-up time (faster crystals will start faster), but this parameter is fixed for 32 KHz crystals.
