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3. Input Clocks
The Si5332 has three input clock nodes: the XA/XB pair, the CLKIN_2/CLKIN_2# pair, and the CLKIN_3/CLKIN_3# pair.
XA/XB supports a crystal input or an external clock input whereas the CLKIN_x/CLKIN_x# pairs support ONLY external clock inputs.
The GPIO pins can be set to select the active input clock for the PLL (or the user can set the active input via register writes).
3.1 Input Clock Terminations
Supported input clock sources for the Si5332 are:
1. External crystal attached to the Si5332 XA/XB inputs.
2. External single-ended clock attached to XA (XA/CLKIN1 pin).
3. Externally supplied clock attached to available CLKIN_x/CLKINx# inputs.
3.1.1 External Crystal
An external crystal can be connected to the Si5332’s XA/XB inputs as shown below. See Table 5.4 in the Si5332 Data Sheet for crystal
specifications when selecting a crystal. Note that the external crystal specifications in Si5332 Data Sheet must be met. A list of recom-
mended AEC-Q200 qualified crystals for the Si5332 can be found in the Silicon Labs document “
Recommended Crystal Reference
Manual for Si5332, Si5357, and Si5225x Automotive Grade Clock Generators
.”
Figure 3.1. External Crystal Connection
3.1.2 External Input Clock on XA Input
The XA input (XA/CLKIN1 pin) can accept an externally supplied, AC-coupled clock with maximum voltage swing of 1 Vpp. See figure
below for connection details. The XB pin must be left open with nothing connected. If using this input clock mode, it is suggested to zero
out the internal crystal loading capacitance (CL) for best performance.”
0.1 µF
Figure 3.2. External Input Clock on XA Input
Si5332-AM1/2/3 Automotive Grade Device Reference Manual
Input Clocks
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