© NXP Laboratories UK 2012
JN-DS-JN5142 1v0
85
B.2 32MHz Oscillator
The JN5142 contains the necessary on-chip components to build a 32 MHz reference oscillator with the addition of
an external crystal resonator, two tuning capacitors. The schematic of these components are shown in Figure 52.
The two capacitors, C1 and C2, will typically be 15pF ±5% and use a COG dielectric. For a detailed specification of
the crystal required and factors affecting C1 and C2 see Appendix B.1. As with all crystal oscillators the PCB layout is
especially important, both to keep parasitic capacitors to a minimum and to reduce the possibility of PCB noise being
coupled into the oscillator.
XTALOUT
C2
C1
R1
XTALIN
JN5142
Figure 52: Crystal Oscillator Connections
The clock generated by this oscillator provides the reference for most of the JN5142 subsystems, including the
transceiver, processor, memory and digital and analogue peripherals.
32MHz Crystal Requirements
Parameter
Min
Typ
Max
Notes
Crystal Frequency
32MHz
Crystal Tolerance
40ppm
Including temperature
and ageing
Crystal ESR Range (Rm)
10
60
See below for more
details
Crystal Load Capacitance
Range (CL)
6pF
9pF
12pF
See below for more
details
Not all Combinations of Crystal Load Capacitance and ESR are Valid
Recommended Crystal
Load Capacitance 9pF and max ESR 40
External Capacitors (C1 & C2)
For recommended Crystal
15pF
CL = 9pF, total external
capacitance needs to be
2*CL. , allowing for stray
capacitance from chip,
package and PCB