A Comparison of the NBC12429 and MC12429 Programmable PLL Clock Synthesizers

AND8120/D
A Comparison of the
NBC12429 and MC12429
Programmable PLL Clock
Synthesizers
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Prepared by: Terry McHenry, FAE
Joseph Hughes
IC Design Engineer
ON Semiconductor
APPLICATION NOTE
Timing Comparison
At a lower level, process technology is a good way to
compare parts, but the real test comes in the performance
comparison.
Table 1 compares some of the key timing parameters for
the parts. As can be seen, the silicon-based parts are nearly
identical, leading to high confidence of a drop-in solution;
the same cannot be said of Motorola’s SiGe part.
Note that the jitter performance of the ON Semiconductor
part is significantly better than the Motorola parts. Figure 1
shows both the cycle-to-cycle RMS jitter and the
cycle-to-cycle peak-to-peak jitter for the silicon parts. Not
only is the NBC12429 jitter significantly lower than the
MC12429, but there is also less jitter variation over the VCO
range.
When it comes to PLL performance these data sheet
specifications only tell part of the story. A great deal of
engineering effort was also expended on the two most
difficult attributes of the Motorola part to duplicate, the
crystal oscillator and the loop dynamics.
The crystal oscillator is very flexible; it will accept low Q,
medium Q, and high Q crystals from 10MHz to 20MHz.
Achieving this took several iterations, but it is important for
a drop-in replacement to be able to operate equally well
from any reasonable crystal. A replacement clock
synthesizer should not have the engineer hunting for a new
crystal as well.
Loop dynamics are characterized by lock time (loop
bandwidth) and overshoot. Table 2 contains laboratory
measurements of the two silicon devices (taken from several
lots and several date codes) showing how closely they
compare. Figures 5 and 6 illustrate graphically that lock time
and overshoot are very similar, with no ringing. It is
important to note that both Table 2 and Figures 5 and 6 depict
a very large frequency step, from 200MHz to 400MHz.
INTRODUCTION
ON Semiconductor, recognizing that companies need to
focus their engineering resources on new products instead of
re-engineering products already in production, has created
direct drop-in replacements for three Motorola clock
synthesizers.
Motorola recently announced their decision to migrate the
MC12429, MC12430, and MC12439 to a new process. This
migration means that existing customers will need to do a
complete evaluation of Motorola’s new parts to insure
compatibility with existing designs.
This paper presents a side-by-side comparison of key
specifications for the ON Semiconductor NBC12429 and
the Motorola MC12429 (at the time this paper was written
the NBC12430 and NBC12439 had not been released;
however, they should also be very similar to their Motorola
counterparts).
Process Technology
Motorola’s MC12429 uses a process called BIC75, which
is an older BiCMOS process, while Motorola’s new part
uses a completely different SiGe process. The control
section of the EOL’ed MC12429 is CMOS but the PLL
portion, the heart of the chip, is bipolar.
ON Semiconductor decided to create a drop in part using
their highly successful MOSAIC V (M5) process, the same
bipolar process that is used to produce some of the fastest
ECL available, ECLinPS Plus (see www.onsemi.com for
more details on the EP and LVEP families). It was also
decided to create this part as a fully differential design to
decrease noise generation and increase power supply
rejection.
ON Semiconductor could have produced this part in SiGe
as well but an all silicon bipolar approach made duplication
of the existing critical timing much easier to achieve.
 Semiconductor Components Industries, LLC, 2003
May, 2003 - Rev. 0
1
Publication Order Number:
AND8120/D
AND8120/D
Table 1
Specification
ON
Motorola
Motorola
Part Number
NBC12429
MC12429
MPC9229
Package
28-Lead PLCC
and 32-Lead LQFP
28-Lead PLCC
and 32-Lead LQFP
28-Lead PLCC
and 32-Lead LQFP
Supply Voltage Range
3.3V - 5V
3.3V – 5V
3.3V
Maximum Input Frequency, XTAL (MHz)
20
20
20
Maximum Input Frequency, S_Clock (MHz)
10
10
10
Output Frequency Range (MHz)
25 - 400
25 – 400
25 - 400
Maximum PLL Lock Time (ms)
10
10
10
Jitter, Cycle to Cycle, Peak-to-Peak (ps)
±20
±25
±95
Setup Time (ns)
20
20
20
Hold Time (ns)
20
20
20
Min/Max Rise/Fall Time (ps)
175 - 425
300 – 800
50 - 300
Output Duty Cycle, Min/Max (%)
47.5/52.5
Not Spec’ed
45/55
ICC, Including PLL (mA)
96
120
120
Table 2
Specification
(Sample lot, 3.3V, 25C)
ON
NBC12429
Motorola
MC12429
Lock Time (ms)
1.09
1.04
Overshoot (%)
1.25
1.00
Duty Cycle @ 200MHz/400MHz (%)
50.1/49.6
48.9/48.6
Tr @ 200MHz/400MHz (ps)
293/296
446/426
Tf @ 200MHz/400MHz (ps)
319/297
397/415
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2
25
25
20
20
RMS Jitter (ps)
RMS Jitter (ps)
AND8120/D
15
ON N=8
10
ON N=4
ON N=2
ON N=1
5
0
100
200
15
300
400
VCO Frequency (MHz)
0
100
500
200
300
400
VCO Frequency (MHz)
500
Figure 2. MC12429 Cycle to Cycle RMS Jitter
vs. VCO Frequency
160
140
140
120
120
P-P Jitter (ps)
P-P Jitter (ps)
MC N=2
MC N=1
5
160
100
80
ON N=8
ON N=4
ON N=2
ON N=1
40
MC N=4
10
Figure 1. NBC12429 Cycle to Cycle RMS Jitter
vs. VCO Frequency
60
MC N=8
MC N=8
100
80
MC N=4
60
MC N=2
MC N=1
40
20
20
0
100
200
300
400
VCO Frequency (MHz)
0
100
500
Figure 3. NBC12429 Cycle to Cycle Peak-Peak
Jitter vs. VCO Frequency
200
300
400
VCO Frequency (MHz)
Figure 4. MC12429 Cycle to Cycle Peak-Peak
Jitter vs. VCO Frequency
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3
500
AND8120/D
Figure 5. NBC12429
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4
AND8120/D
Figure 6. MC12429
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5
AND8120/D
Conclusion
In order to have a high degree of confidence in a drop-in
solution, a clock synthesizer must have both similar timing
and similar dynamics to the part it is replacing. The
NBC12429 compares very favorably to the MC12429 on
both counts, and should require a minimum of engineering
effort.
The NBC12429 is produced at ON Semiconductor’s fab
in Phoenix, Arizona and is available today in sample or
production quantities from your local distributor. The
NBC12429 is available in either a 28 pin PLCC
(NBC12429FN) or a 32 pin LQFP (NBC12429FA).
For more information click on:
https://www.onsemi.com/productSummary/0,4317,NBC1
2429,00.html.
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