Reference Manual

USB-KW24D512
USB-KW2x Hardware Reference Manual, Rev. 0.1
Freescale Semiconductor 3-5
3.2.2 Clocks
The USB-KW24D512 provides one clock:
• 32 MHz Reference Oscillator — Figure 3-5 shows the external 32 MHz external crystal Y1. This
mounted crystal must meet the specifications outlined in the AN3251 application note. The IEEE
802.15.4 Standard requires that the frequency be accurate to less that +/-40 ppm.
— Capacitors C10 and C11 provide the bulk of the crystal load capacitance. Onboard trim
capacitors can be programmed to center the frequency. At 25°C, it is desired to have the
frequency accurate to +/-10 ppm or less to allow for temperature variation.
— To measure the 32 MHz oscillator frequency, signal CLK_OUT (TP5) can optionally be
programmed to provide a buffered output clock signal.
Figure 3-5. USB-KW24D512 32 MHz Reference Oscillator Circuit
3.2.3 Power Management
The USB-KW24D512 power management circuit is shown in Figure 3-6.