When choosing a crystal for the 32768 Hz Slow Clock Oscillator or
for the 3 MHz–20 MHz oscillator, users need to consider several parameters. Important
parameters between crystal and product specifications are as follows:
- Crystal Load Capacitance
- The total capacitance loading the crystal, including the
oscillator’s internal parasitics and the PCB parasitics, must match the load
capacitance for which the crystal’s frequency is specified. Any mismatch in the
load capacitance with respect to the crystal’s specification will lead to
inaccurate oscillation frequency.
- Drive Level
- Crystal drive level ≥ Oscillator Drive Level. Having a
crystal drive level number lower than the oscillator specification may damage the
crystal.
- Equivalent Series Resistor (ESR)
- Crystal ESR ≤ Oscillator ESR Max. Having a crystal with
ESR value higher than the oscillator may cause the oscillator to not start.
- Shunt Capacitance
- Max. crystal shunt capacitance ≤ Oscillator Shunt
Capacitance (CSHUNT). Having a crystal with
CSHUNT value higher than the oscillator may
cause the oscillator to not start.