AND8120/D A Comparison of the NBC12429 and MC12429 Programmable PLL Clock Synthesizers http://onsemi.com 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 http://onsemi.com 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 http://onsemi.com 3 500 AND8120/D Figure 5. NBC12429 http://onsemi.com 4 AND8120/D Figure 6. MC12429 http://onsemi.com 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. ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice to any products herein. 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