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Topic: "Easy" to use clock chip? (Read 4023 times) previous topic - next topic


This isn't really Arduino related, but I thought I'd post here because all the guys on the Arduino forum seem to put an emphasis on ease of use (and it IS for a shield)... but I'm wondering whether there is an easy to use PLL clock chip.  Surface mount is ok.  400Mhz and maybe some outputs that are less (or selectable)...  I've been looking at a cypress part CY22394FXC, but you have to program it and it seems like doing so is so complicated that Cypress had to write a special piece of programmer software to help you out!



It depends on what you frequency you want to get at, and from what frequency you start with.

Most simple PLLs need a dividing ratio programming into them. Where it gets difficult is where you require a none integer relationship between the reference frequency and the required frequency. It can be tricky to work this out and that is when specialised software or application notes can come in.

Also the phase jitter from none integer PLLs can be a problem.
In short they all work in much the same way and so need setting up in much the same way.


Jun 18, 2009, 08:58 pm Last Edit: Jun 19, 2009, 07:01 am by zooto68 Reason: 1
What kind of uses would you put one of these IC's to with an Arduino out of curiosity?


@Grumpy_Mike I'm really just fooling around, so all I need is "much faster than the Arduino"; so perhaps I don't need a non-integral relationship.

@Mike Mc
That question really deserves its own posting in the forum so other people can chime in.  But let me summarize here and maybe repost later...

In terms of uses, it seems like one CPLD can take the place of some of the logic portion of some special purpose chips that people are using.  Here are my ideas:

1. 5 to 3 volt converter (I thought to use a 5V tolerant CPLD)
2. IO multiplexer/demultiplexer  (of course, the new MEGA on the 1280 has a lot of IOs...)
3. Interrupt multiplexer

Then there is basic logic that can be implemented in the CPLD.  This logic could also be implemented in the AVR of course, but some of them are more efficiently done in a non-Von Neumann hardware architecture.

4 Button state sensing debouncing
5 Simple logic around other sensors (IR for example), like filtering false signal.
5 Stepper motor control (LOTS of motors)
6. USB to serial (may not fit)

Then there is some stuff that would benefit from a high clock rate:
7. PWM outputs
8. therefore LED drivers (but not power LEDs)
9. LED matrix controllers > 8x8
10. Video signal driver (I haven't really looked into it; but without a DAC this might not really work -- could you use PWM and an inductor to smooth out the signal?)

Also, I think that it would be great for educational purposes; the combination of Arduino + CPLD is a simple model for a modern CPU + chipset.

But the most important reason is because it will be fun! :-)


OK have a look at the LTC6903 From Linear. That goes from 1KHz to 68MHz and is simple enough to drive and is set through SPI. The LTC6904 is the same thing but with an I2C interface.


Thanks!  It looks like that chip has 14 bits of frequency selection; it would be pretty cool to connect to the arduino & a pot to make an adjustable clock.

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