NRF2402 Datasheet, PDF (25/31 Pages) List of Unclassifed Manufacturers – Single chip 2.4 GHz Transmitter

PRODUCT SPECIFICATION
nRF2402/nRF2402G Single Chip 2.4 GHz Radio Transmitter
Sharing crystal with micro controller.
When using a micro controller to drive the crystal reference input XC1 of the
nRF2402/nRF2402G transmitter some rules must be followed.
Crystal parameters:
When the micro controller drives the nRF2402/nRF2402G XC1 input, all crystal load
parameters (C_L, C₀, ESR) are set by the micro controller specification. The frequency
accuracy (±30 ppm) is still set by the nRF2402/nRF2402G specification. The
nRF2402/nRF2402G will load the crystal circuitry of the micro controller by XC1 input
capacitance (0.5pF) plus PBC routing paracitics.
External reference input amplitude & Current consumption
The reference input should never have signal levels exceeding rail voltages. Exceeding rail
voltage will excite the ESD structure and the radio performance is degraded below
specification. Applying reference sources without DC bias will bring the reference signal
under GND level, and this 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 17 Principle of crystal oscillator
It is hence recommended to use a DC-block before the XC1 pin so that the internal ESD
structures will self bias the XC1 voltage.
The nRF2402/nRF2402G 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
Nordic Semiconductor ASA - Vestre Rosten 81, N-7075 Tiller, Norway - Phone [phone] - Fax [phone]
Revision: 2.0
Page 25 of 31
April 2005