Said/Didier, There just must be something special about Philip's PLL designs. Way back when when I was working in the underwater world we used a small underwater range finder (sonar) that used the Philips 4046 PLL. The Philips part was the ONLY 4046 that would meet the range and jitter specs. We used other parts if we needed to test something and weren't too concerned about accuracy, but none of those sonars ever SHIPPED without the Philips part inside.
Randy ________________________________________________________________________ ________________________________ -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Tuesday, August 08, 2006 11:08 PM To: time-nuts@febo.com Subject: Re: [time-nuts] Frequency Dividers In a message dated 8/8/2006 19:51:06 Pacific Daylight Time, [EMAIL PROTECTED] writes: Hi Didier, On the PLL: Philips typically does very well on their PLL's - jitter is very low. Certainly I've seen some of their PLL's in the ps range, which would put the 1PPS output at probably better than 1E-11, 1s accuracy. I can measure the unit I have, and let you know later... bye, Said I have used a number of pll controlled microcontrollers, and I would not recommend using one of those in a timing application such as those discussed here. These PLLs are generally not very clean spectrally (it's actually a good thing for EMI, some chips have purposeful spread spectrum clocks) and may have lots of jitter. However, most of the chips with PLL will let you disable the PLL and run from a crystal or an external oscillator. Alternately, it you use the timer instead of software loops, you can run the core from the PLL as long as the timer itself is not driven from the PLL. I use the Silabs C8051F133 in several projects and it will run with up to a 100 MHz clock (with many instructions running in one clock cycle) from the PLL or I believe 50 MHz with an external oscillator. And if you needed a 16 x 16 MAC engine for that counter, it has that too :-) http://www.silabs.com/public/documents/tpub_doc/dsheet/Microcontrollers/ Precis ion_Mixed-Signal/en/C8051F12x-13x.pdf That's not your father's 8051!!! For timing applications, it has 5 general purpose 16 bit timers and a 6 channel 16 bit Programmable Counter Array, so by using one of the 16 bit timer as a prescaler for the PCA, you can have create up to 10 low-jitter timer outputs with 6 of them having up to 32 bits capacity, with minimum software overhead, so the CPU is mostly available for anything else you might want to do with it.. Pretty neat, uh? The other day, a rep for a well known semiconductor/microcontroller company that shall remain nameless was showing me their latest ad for an 8051 running at 50 MHz with a 4 clock core and in big letters: FASTEST 8051 AVAILABLE. I pointed him to the Silabs web site and left him there... Didier KO4BB PS: only problem for the hobbyist, it only comes in a surface mount 64 or 100 pins TQFP (cheap development boards are available, with JTAG programmer, prototyping area and serial interface). I am not associated with Silabs, however I am a very satisfied customer and I can recommend their products (hardware and software), they are topnotch and Silabs customer service is excellent. I routinely use them in products that operate way outside the generous -40 to +85 C temperature range without any problem. _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
