NRF2401A Datasheet, PDF (32/38 Pages) List of Unclassifed Manufacturers – Single chip 2.4 GHz Transceiver

PRODUCT SPECIFICATION
nRF2401A Single Chip 2.4 GHz Radio Transceiver
Sharing crystal with micro controller.
When using a micro controller to drive the crystal reference input XC1 of the
nRF2401A transceiver some rules must be followed.
Crystal parameters:
When the micro controller drives the nRF2401A clock input, the requirement of load
capacitance C_L is set by the micro controller only. The frequency accuracy of 30 ppm
is still required to get a functional radio link. The nRF2401A will load the crystal by
0.5pF at XC1 in addition to the PBC routing.
Input crystal amplitude & Current consumption
The input signal should not have amplitudes exceeding any rail voltage, but any DC-
voltage within this is OK. Exceeding rail voltage will excite the ESD structure and the
radio performance is degraded below specification. If testing the nRF2401A with a
RF source with no DC offset as the reference source, the input signal will go below
the ground level, which is not acceptable.
XO_OUT
Buffer:
Sine to
full swing
Amplitude
controlled
current source
Current starved
inverter:
XOSC core
Vdd
Vdd
Vss
ESD
XC1
Vss
ESD
XC2
Figure 19 Principle of crystal oscillator
It is recommended to use a DC-block before the XC1 pin so that the internal ESD
structures will self bias the XC1 voltage .
The nRF2401A crystal oscillator is amplitude regulated. To achieve low current
consumption and also good signal-to-noise ratio, it is recommended to use an input
signal larger than 0.4 V-peak. The needed input swing is independent of the crystal
Nordic Semiconductor ASA - Vestre Rosten 81, N-7075 Tiller, Norway - Phone [phone] - Fax [phone]
Revision: 1.0
Page 32 of 38
December 2004