CP3BT23 Datasheet, PDF (53/260 Pages) Texas Instruments – CP3BT23 Reprogrammable Connectivity Processor with Bluetooth and Dual CAN Interfaces

11.1 EXTERNAL CRYSTAL NETWORK
An external crystal network is connected to the X1CKI and
X1CKO pins to generate the Main Clock, unless an external
clock signal is driven on the X1CKI pin. A similar external
crystal network may be used at pins X2CKI and X2CKO for
the Slow Clock. If an external crystal network is not used for
the Slow Clock, the Slow Clock is generated by dividing the
fast Main Clock.
The crystal network you choose may require external com-
ponents different from the ones specified in this datasheet.
In this case, consult with National’s engineers for the com-
ponent specifications
12 MHz
Crystal
C1
C2
X1CKI
X1CKO
The crystals and other oscillator components must be
placed close to the X1CKI/X1CKO and X2CKI/X2CKO de-
vice input pins to keep the printed trace lengths to an abso-
lute minimum.
Figure 5 shows the external crystal network for the X1CKI
and X1CKO pins. Figure 6 shows the external crystal net-
work for the X2CKI and X2CKO pins. Table 21 shows the
component specifications for the main crystal network, and
Table 22 shows the component specifications for the 32.768
te ^{kHz crystal network.}
GND
DS189
Figure 5. Main Clock External Crystal Network
X2CKI
C1
32.768 kHz
Crystal
X2CKO
le_C2
o _GND
DS215
Figure 6. Slow Clock External Crystal Network
s _{Table 21 Component Values of the High Frequency Crystal Circuit}
b Component
O ^Crystal
Parameters
Resonance Frequency
Type
Max. Serial Resistance
Max. Shunt Capacitance
Values
12 MHz ± 20 ppm
AT-Cut
50 Ω
7 pF
Tolerance
N/A
Load Capacitance
22 pF
Capacitor C1, C2
Capacitance
22 pF
20%
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