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nRF24AP2-USB Product Specification

To ensure a functional radio link the frequency accuracy must be

± 50 ppm or better. The initial tolerance of

the crystal, drift over temperature, aging and frequency pulling due to incorrect load capacitance must all

be taken into account. For reliable operation the crystal load capacitance, shunt capacitance, equivalent

series resistance (ESR) and drive level must comply with the specifications in Table 17. on page 34. It is

recommended to use a crystal with lower than maximum ESR if the load capacitance and/or shunt capaci-

tance is high. This will give faster start-up and lower current consumption.

6.3.2

External 16 MHz clock

nRF24AP2 may be used with an external 16 MHz clock applied to the XC1 pin. The input signal must be

analog, coming from the crystal oscillator of a microcontroller, for example. An input amplitude of 0.8V

peak-to-peak or higher is recommended to achieve low current consumption and a good signal-to-noise

ratio. The DC level is not important as long as the applied signal never rises above VDD or drops below

VSS. The XC1 pin will load the microcontroller’s crystal with approximately 1pF in addition to PCB routing.

XC2 shall not be connected.

Note: A frequency accuracy of

±50 ppm or better is required to get device performance as outlined

in chapter 8 on page 33.