JN516X Datasheet, PDF (88/94 Pages) NXP Semiconductors – IEEE802.15.4 Wireless Microcontroller

Three examples of typical crystals are given, each with the value of external capacitors to use, plus the likely supply
current and start-up time that can be expected. Also given is the maximum recommended ESR based on the start-up
criteria given in Appendix B.1.3. The values of the external capacitors can be calculated using the equation in
Appendix B.1.2 .
Load Capacitance
Ext Capacitors
Current Start-up Time
Max ESR
9pF
15pF
1.6µA
0.8Sec
70KΩ
6pF
9pF
1.4µA
0.6sec
80KΩ
12.5pF
22pF
2.4µA
1.1sec
35KΩ
Below is measurement data showing the variation of the crystal oscillator supply current with voltage and with crystal
ESR, for two load capacitances.
32KHz Crystal Oscillator Current
1.6
1.4
1.2
1
0.8
0.6
2.2
2.4
2.6
2.8
3
3.2
3.4
3.6
Supply Voltage (VDD)
32KHz Crystal Oscillator Current
1.6
1.4
1.2
9pF
1
12.5pF
0.8
0.6
10
20
30
40
50
60
70
80
Crystal ESR (K ohm)
88
JN-DS-JN516x v1.1 Production
© NXP Laboratories UK 2013