NRF2402G Nordic VLSI, NRF2402G Datasheet - Page 25

• Manufacturer Part Number: NRF2402G
• Manufacturer: Nordic VLSI

PRODUCT SPECIFICATION
nRF2402 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
transmitter some rules must be followed.
Crystal parameters:
When the micro controller drives the nRF2402 XC1 input, all crystal load parameters (C
ESR) are set by the micro controller specification. The frequency accuracy (±30 ppm) is still
set by the nRF2402 specification. The nRF2402 will load the crystal circuitry of the micro
controller by XC1 input capacitance (0.5pF) plus PBC routing parasitic.
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.
It is hence recommended to use a DC-block before the XC1 pin so that the internal ESD
structures will self biases the XC1 voltage.
The nRF2402 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 frequency. When using external
crystal reference, XC2 is not used and can be left as an open pin.
Nordic Semiconductor ASA
Revision: 2.1
-
Vestre Rosten 81, N-7075 Tiller, Norway
Figure 16 Principle of crystal oscillator
Vss
ESD
Vdd
XC1
Page 25 of 32
current source
Current starved
-
XO_OUT
full swing
XC2
Amplitude
controlled
Sine to
Buffer:
XOSC core
inverter:
Phone [phone]
ESD
Vdd
Vss
- Fax [phone]
March 2006
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