Electronic – Having Trouble Identifying Crystal Oscillator Symbol

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I'm working on a circuit implementing the TI CC2640R2F (Datasheet) which requires an external 24MHz crystal oscillator to function. In the schematic (pg. 42), it shows what looks like a normal oscillator symbol but with extra brackets and wires on it.
This is a clipping from the example schematic
Excuse the poor drawn in IC connections, pin designations are on pg. 10 and state that this X24M_N/P are "24-MHz crystal oscillator pin 1/2". I have 3 questions:
1. Why does the symbol look like this rather than the standard oscillator symbol
2. What are the four different pins?
3. Why does the oscillator right next to it in the schematic use the normal symbol?

Best Answer

This is one of the crystals in a flat metal can with four pins. Two of the pins connect to the crystal, and the other two to the can. Those last two should be connected to ground. The can then acts like a shield.

In your schematic, pins 1 and 3 are the crystal connections, and pins 2 and 4 connect to the can.