BC66F840 Datasheet, PDF (47/242 Pages) Holtek Semiconductor Inc – 2.4GHz Flash RF TX/RX MCU

BC66F840/BC66F850/BC66F860
2.4GHz Flash RF TX/RX MCU
External Crystal/Ceramic Oscillator – HXT
The External Crystal/Ceramic System Oscillator is the high frequency oscillator. For most crystal
oscillator configurations, the simple connection of a crystal across OSC1 and OSC2 will create the
necessary phase shift and feedback for oscillation, without requiring external capacitors. However,
for some crystal types and frequencies, to ensure oscillation, it may be necessary to add two small
value capacitors, C1 and C2. Using a ceramic resonator will usually require two small value
capacitors, C1 and C2, to be connected as shown for oscillation to occur. The values of C1 and C2
should be selected in consultation with the crystal or resonator manufacturers specification.
For oscillator stability and to minimise the effects of noise and crosstalk, it is important to ensure
that the crystal and any associated resistors and capacitors along with inter connecting lines are all
located as close to the MCU as possible.
C1
O SC1
In te r n a l
O s c illa to r
C ir c u it
Rp
Rf
T o in te r n a l
C2
O SC2
c ir c u its
N o te : 1 . R p is n o r m a lly n o t r e q u ir e d . C 1 a n d C 2 a r e r e q u ir e d .
2 . A lth o u g h n o t s h o w n O S C 1 /O S C 2 p in s h a v e a p a r a s itic
c a p a c ita n c e o f a r o u n d 7 p F .
Crystal/Resonator Oscillator – HXT
Crystal Oscillator C1 and C2 Values
Crystal Frequency
C1
C2
16MHz
0pF
0pF
Note: C1 and C2 values are for guidance only.
Crystal Recommended Capacitor Values
Rev. 1.40
47
May 24, 2017