NRF2401AG Nordic VLSI, NRF2401AG Datasheet - Page 33

• Manufacturer Part Number: NRF2401AG
• Manufacturer: Nordic VLSI

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
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.
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
Revision: 1.1
L
is set by the micro controller only. The frequency accuracy of 30 ppm
- Vestre Rosten 81, N-7075 Tiller, Norway
Figure 19 Principle of crystal oscillator
Vss
ESD
Vdd
XC1
Page 33 of 40
current source
Current starved
XO_OUT
full swing
XC2
Amplitude
controlled
Sine to
Buffer:
XOSC core
-
inverter:
ESD
Phone [phone]
Vdd
Vss
-
Fax [phone]
March 2006