mc145156 Lansdale Semiconductor, Inc., mc145156 Datasheet - Page 30

• Manufacturer Part Number: mc145156
• Description: Pll Frequency Synthesizer Family
• Manufacturer: Lansdale Semiconductor, Inc.

ML1451xx
Method of Measurement”, Proc. IEEE, Vol. 57, No. 2
Feb.,1969.
FrequencyControl”, Electro–Technology, June, 1969.
Design, May, 1966.
OVERVIEW
lished as a method of achieving high performance frequency
synthesizer operation at high frequencies. Basically, the
approach allows relatively low–frequency programmable coun-
ters to be used as high–frequency programmable counters with
speed capability of several hundred MHz. This is possible with
out the sacrifice in system resolution and performance that
results if a fixed (single–modulus) divider is used for the
prescaler.
be uniquely configured. Special control logic is necessary to
select the divide value P or P + 1 in the prescaler for the
required amount of time (see modulus control definition).
Lansdale's dual–modulus frequency synthesizers contain this
feature and can be used with a variety of dual–modulus-
prescalers to allow speed, complexity and cost to be tailored to
the system requirements. Prescalers having P, P + 1 divide val-
ues in the range of ÷ 3/÷4 to ÷128/÷ 129 can be controlled by
most Lansdale frequency synthesizers.
with the MC145152 (Motorola), ML145156, or ML145158 are:
Page 30 of 35
Technical Note TN–24, Statek Corp.
Technical Note TN–7, Statek Corp.
E. Hafner, “The Piezoelectric Crystal Unit – Definitions and
D. Kemper, L. Rosine, “Quartz Crystals for
P. J. Ottowitz, “A Guide to Crystal Selection”, Electronic
The technique of dual–modulus prescaling is well estab-
In dual–modulus prescaling, the lower speed counters must
Several dual–modulus prescaler approaches suitable for use
ML12009
ML12011
ML12013
ML12015
ML12016
ML12017
ML12018
MC12028A
MC12034
MC12038
ML12052
ML12054A
DUAL–MODULUS PRESCALING
RECOMMENDED READING
÷127/128 or ÷255/256
÷
÷
÷
64/65 or
64/65 or
÷32/33 or ÷64/65
32/33 or
÷
÷
÷
÷
÷
128/
÷
÷
10/
32/
40/
64/
5/
8/
NOTE: Lansdale and Motorola do not recommend one supplier over another and in no
÷
÷
÷
÷
÷
÷
÷
÷
÷
÷
129
6
9
11
33
41
65
128/129
128/129
64/65
way suggests that this is a complete listing of crystal manufacturers.
Table 1. Partial List of Crystal Manufacturers
440 MHz
500 MHz
500 MHz
225 MHz
225 MHz
225 MHz
520 MHz
1.1 GHz
2.0 GHz
1.1 GHz
1.1 GHz
2.0 GHz
United States Crystal Corp.
www.lansdale.com
Crystek Crystal
Fox Electronics
Statek Corp.
DESIGN GUIDELINES
by the application:
number programmed into the ÷ A counter, P and P + 1 are the
two selectable divide ratios available in the dual–modulus
prescalers. To have a range of N T values in sequence, the
÷ A counter is programmed from zero through P – 1 for a par-
ticular value N in the ÷ N counter. N is then incremented to N
+ 1 and the ÷ A is sequenced from 0 through P – 1 again.
achieved for N T . These values are a function of P and the size
of the ÷ N and ÷ A counters.
N min ≥ P – 1. Then N T min = (P – 1) P + A or (P – 1) P since
A is free to assume the value of 0.
prescaler output must go from low to high after each group of
P or P + 1 input cycles. The prescaler should divide by P when
its modulus control line is high and by P + 1 when its MC is
low.
value used for P must be large enough such that:
can be achieved by choosing the values for P of 8, 16, 32, or
64. For these cases, the desired value of N T results when N T
in binary is used as the program code to the ÷ N and ÷ A coun-
ters treated in the following manner:
The system total divide value, N total (N T ) will be dictated
N is the number programmed into the ÷ N counter, A is the
There are minimum and maximum values that can be
The constraint N ≥ A always applies. If A max = P – 1, then
To maximize system frequency capability, the dual–modulus
For the maximum frequency into the prescaler (f VCOmax ), the
1.f VCO max divided by P may not exceed the frequency
2.The period of f VCO divided by P must be greater than the
A sometimes useful simplification in the programming code
1.Assume the ÷A counter contains “a” bits where 2 a ≥P.
2.Always program all higher order ÷A counter bits above
a. Propagation delay through the dual–modulus prescaler.
b. Prescaler setup or release time relative to its MC signal.
c. Propagation time from f in to the MC output for the
capability of f in (input to the ÷ N and ÷ A counters).
sum of the times:
“a” to 0.
frequency synthesizer device.
N T =
frequency into the phase detector
frequency into the prescaler
NT max = N max • P + A max
LANSDALE Semiconductor, Inc.
= N • P + A
Issue A