CC2400 Chipcon AS, CC2400 Datasheet - Page 47

• Manufacturer Part Number: CC2400
• Description: 2.4 GHz RF Transceiver
• Manufacturer: Chipcon AS

Crystal Oscillator
An external clock signal or the internal
crystal oscillator can be used as main
frequency
frequency must be 16 MHz. Because the
crystal frequency is used as reference for
the data rate as well as other internal
signal
frequencies cannot be used.
If an external clock signal is used this
should be connected to XOSC16_Q1,
while XOSC16_Q2 should be left open.
The MAIN.XOSC16M_BYPASS bit must be
set when an external clock signal is used.
Using the internal crystal oscillator, the
crystal must be connected between the
XOSC16_Q1 and XOSC16_Q2 pins. The
oscillator is designed for parallel mode
operation of the crystal. In addition,
loading capacitors (C5 and C6) for the
crystal are required. The loading capacitor
values
capacitance, C
The total load capacitance seen between
the crystal terminals should equal C
the crystal to oscillate at the specified
frequency.
Chipcon AS
depend
processing
reference.
Table 11. 16MHz crystal oscillator component values for C
SmartRF
L
, specified for the crystal.
XOSC_Q1
XOSC_Q1
on
®
CC2400 PRELIMINARY Datasheet (rev. 1.1), 2003-10-02
functions,
the
The
Figure 21. Crystal oscillator circuit
Item
C5
C6
total
reference
C5
C5
other
L
load
for
XTAL
XTAL
XTAL
SmartRF
C
The parasitic capacitance is constituted by
pin input capacitance and PCB stray
capacitance.
capacitance is typically 5 pF. A trimming
capacitor may be placed across C6 for
initial tuning if necessary.
The crystal oscillator circuit is shown in
Figure 21. Typical component values for
different values of C
11.
The
regulated. This means that a high current
is used to start up the oscillations. When
the amplitude builds up, the current is
reduced to what is necessary to maintain
a stable oscillation. This ensures a fast
start-up and keeps the drive level to a
minimum. The ESR of the crystal should
be within the specification in order to
ensure
Electrical Specifications section).
C
L
22 pF
22 pF
= 16 pF
L
=
C
crystal
1
5
a
C6
C6
+
1
C
reliable
1
6
+
oscillator
XOSC_Q2
XOSC_Q2
The
C
®
parasitic
L
L
start-up
=16pF
are given in Table
CC2400
total
is
Page 47 of 73
(see
amplitude
parasitic
the