8MHz / 40MHz Pierce Oscillator - X-FAB XT018-0.18µm

The TS_XOSC_40M_X8 is a 8MHz / 40MHz Pierce oscillator that generates a VCC-level logic square wave when a 8MHz / 40MHz quartz crystal is connected between its output XOUT and input XIN with external grounded load capacitors. If there is no quartz crystal and load capacitors present, and XIN is hardwired externally to 0V, the circuit only forwards the external clock signal applied on XOUT through its internal Schmitt-trigger circuit to the output FOUT.

The circuit operates with the supply voltage VCC (3.3V typical) and features an enable signal EN. The Pierce oscillator consists of an amplitude regulation feedback loop which ensures that the amplitude of stable oscillations are limited, so that the crystal maximum drive level is not exceeded. The Pierce oscillator can be followed by the TES IP clock buffer circuit TS_CLKBUF_25pF_X8 which allows driving loads of maximum total capacitance of 25pF while maintaining rise-/fall times in the range of 1.5ns to 3ns.

OPERATING CONDITIONS

• Dual Frequency Support: 8MHz or 40MHz operation based on crystal choice.
• Flexible Operation Modes:
  • Crystal Mode: Uses a quartz crystal between XIN and XOUT pads, with external grounded load capacitors.
  • External Clock Mode: If no crystal is present and XIN is hardwired to 0V, the oscillator acts as a buffer for an external clock signal on XOUT.
• Drive Level Protection: Built-in amplitude regulation feedback loop prevents crystal overdrive, enhancing long-term reliability.