Handling Notes
Selection of ICs and circuit constants by frequency bands
Frequency
3 to 4.9(MHz)
5 to 6.9(MHz)
7 to 9.9(MHz)
10 to 19.9(MHz)
20 to 30(MHz)
TC74HCU04A
TC7SU04F
TC7WU04FU
TC74VHCU04
TC7SHU04F
TC7WHU04FU
TC4069UB
TC4SU69F
IC
Rf
1M
0()
Rd
Rx
*1
*2
*3
1500()
470()
0()
0()
0 to 1500
6 to 22(pF)
6 to 15(pF)
6 to 15(pF)
C
1
, C
2
*1: Necessary for preventing overtone oscillation and must be changed depending on the frequency band or the C1 and C2 values.
*2: Used to reduce excitation current of the crystal unit. Necessary for stable operation of small-sized crystal units.
*3: The optimum value differs with the values of load capacitance and Rd.
(2) CMOS overtone crystal oscillation circuit
This figure shows a standard CMOS inverter crystal oscillation circuit to oscillate a crystal unit using the overtone mode.
CMOS overtone crystal oscillation circuit
Rf = 1M
L
1
X-tal
C
3
R
1
1000pF
C
1
L
2
C
2
There are same cases when L1 and R1 are matched to the value of load capacitance.
(3) Selection of ICs and circuit constants by frequency bands
Frequency range
20 to 60(MHz)
TC74VHCU04
TC7SHU04F
TC7WHU04FU
IC
C
C
1
2
3 to 10pF
10 to 22pF
(4) Method of selecting circuit constants and functions of elements
C1 : Forms load capacitance of the circuit together with C2, L1 and L2. A value of approx. 5pF is used.
C2 : Forms load capacitance of the circuit together with C1, L1 and L2. Prevents fundamental wave oscillation. Shall be selected
so that C2 comes between the third overtone frequency at which resonance frequency with L2 is to make oscillation and 1/3
of the third overtone frequency. A value of 10 to 22pF is used.
C3 : A bypath capacitor
L1 : A coil to adjust load capacitance of the oscillation circuit to a value near the series. A value of several µH is used.
L2 : Forms load capacitance of the circuit together with C1, C2 and L1. Prevents fundamental wave oscillation. Shall be selected
so that L2 comes between the third overtone frequency at which resonance frequency with C2 is to make oscillation and 1/3
of the third overtone frequency. A value of 10 to 22pF is used.
R1 : A Q dump resistor for L1 . As an element for preventing self-excited oscillation, A value of several k to several tens of
k is used.
* L1 and R1 might not be used.
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KYOCERA AVX [ KYOCERA AVX ]
