MC54HC4060 Motorola, MC54HC4060 Datasheet - Page 7

• Manufacturer Part Number: MC54HC4060
• Description: 14-Stage Binary Ripple Counter with Oscillator
• Manufacturer: Motorola

High–Speed CMOS Logic Data
DL129 — Rev 6
pedance elements should be considered: C out and C a of the amp, feedback resistor R f , and amplifier phase shift error from 180 _ .
Reactance jX e should be positive, indicating that the crystal is operating as an inductive reactance at the oscillation frequency
The maximum R s for the crystal should be used in the equation.
the gain of the HC4060 amplifier.
tance of 32 pF at the required frequency.
of 100,000. In–circuit Q is arbitrarily set at 20% below crystal Q or 80,000. Then R load = (2 f o L s /Q) – R s where L s and R s are
crystal parameters.
Here R = R out + R1. R out is amp output resistance, R1 is Z. The C corresponding to X C is given by C = C1 + C in .
Q = 2 f o L s /(R s + R load ) to find in–circuit Q. If Q is not satisfactory pick another value for R1 and repeat the procedure.
CHOOSING R1
crystal. The drive level specified by the crystal manufacturer
is the maximum stress that a crystal can withstand without
damage or excessive shift in frequency R1 limits the drive
level.
overdrive the crystal, monitor the output frequency as a func-
tion of voltage at Osc Out 2 (Pin 9). The frequency should
increase very slightly as the dc supply voltage is increased.
An overdriven crystal will decrease in frequency or become
unstable with an increase in supply voltage. The operating
supply voltage must be reduced or R1 must be increased in
value it the overdriven condition exists. The user should note
that the oscillator start–up time is proportional to the value of
R1.
SELECTING R f
determines the gain and bandwidth of the amplifier. Proper
bandwidth insures oscillation at the correct frequency plus
roll–off to minimize gain at undesirable frequencies, such as
X e = X C2 + X C +
R load =
Z e =
The following procedure applies for oscillators operating below 2 MHz where Z is a resistor R1. Above 2 MHz, additional im-
Step 1: Calculate the equivalent series circuit of the crystal at the frequency of oscillation.
Step 2: Determine , the attenuation, of the feedback network. For a closed–loop gain of 2, A
Step 3: Determine the manufacturer’s loading capacitance. For example: A manufacturer may specify an external load capaci-
Step 4: Determine the required Q of the system, and calculate R load . For example, a manufacturer specifies a crystal Q
Step 5: Simultaneously solve, using a computer,
Alternately, pick a value for R1 (i.e., let R1 = R s ). Solve Equations 1 and 2 for C1 and C2. Use Equation 3 and the fact that
Power is dissipated in the effective series resistance of the
To verify that the maximum dc supply voltage does not
The feedback resistor, R f , typically ranges up to 20 M . R f
=
R R e + X C2 (X e – X C )
– jX C o + R s + jX L s – jX C s
– jX C o (R s + jX L s – jX C s
RX C o X C2 [(X C + X C2 ) (X C + X C o ) – X C (X C + X C o + X C2 )]
X C X C2
X 2 C2 (X C + X C o ) 2 + R 2 (X C + X C o + X C2 ) 2
R e XC 2
R
= X C load (where the loading capacitor is an external load, not including Co)
(with feedback phase shift = 180 _ )
= R e + jX e
DESIGN PROCEDURES
7
the first overtone. R f must be large enough so as to not affect
the phase of the feedback network in an appreciable manner.
sheet and are hereby acknowledged and recommended for
reading:
March 7, 1985.
Machine Design, April 25, 1985.
ALSO RECOMMENDED FOR READING:
Method of Measurement”, Proc. IEEE, Vol. 57, No. 2, Feb.
1969.
Control”, Electro–Technology, June, 1969.
Design, May, 1966.
ACKNOWLEDGEMENTS AND RECOMMENDED
The following publications were used in preparing this data
Technical Note TN–24, Statek Corp.
Technical Note TN–7, Statek Corp.
D. Babin, “Designing Crystal Oscillators”, Machine Design,
D. Babin, “Guidelines for Crystal Oscillator Design”,
E. Hafner, “The Piezoelectric Crystal Unit – Definitions and
D. Kemper, L. Rosine, “Quartz Crystals for Frequency
P. J. Ottowitz, “A Guide to Crystal Selection”, Electronic
REFERENCES
= 2, = 2/A where A is
MC54/74HC4060
MOTOROLA
(1)
(2)
(3)