Re: [SI-LIST] : re: [SI-LiST]: PLL clock buffer chips and the feedback loop

About this list Date view Thread view Subject view Author view

From: Yu Wang (wangy_km@yahoo.com)
Date: Wed Apr 05 2000 - 21:09:46 PDT


Andy,
I'm not sure if it will be helpful to your case.
whatever you can try. I heard about a delay reset chip
from TI or Maxim(should be one of them, I can check it
later). It generates a delayed reset pulse(the delay
is a big amount of time) after power on.
Good luck.

Yu Wang

--- Andy Peters <apeters@noao.edu> wrote:
> Thanks to all who've responded. Here's what I
> intend to do. I found a TI
> part (CDCF2509) with built-in source terminations
> and nine outputs. The
> oscillator will feed the reference input. The five
> "1Y" outputs will feed
> an FPGA and its four SDRAMs (two of the SDRAMs are
> on top of the board, the
> other two are on the bottom). One of the "2Y"
> outputs will feed a third
> FPGA's clock input. A second "2Y" output will feed
> a second CDCF2509. The
> five "1Y" outputs of the second PLL buffer will feed
> the second FPGA and its
> four SDRAMs. The "2Y" outputs of the second PLL
> buffer will be disabled.
>
> The board has a clocks-only layer, so we don't think
> we'll have too much
> trouble trying to keep the clock line lengths all
> equal.
>
> The only "gotcha" here is that the VME interface
> control chip, a Cypress
> (@#$%!) part, requires an 80 MHz clock, but that
> part has a built-in
> power-on reset circuit that enables it to configure
> itself. That
> configuration fails if the clock is not running, and
> the ~1 ms PLL buffer
> startup time is too long. It seems as if the only
> solution is to run two
> traces from the oscillator - one to the first buffer
> and the second to the
> VME chip. I don't think it's a problem keeping
> those traces equally short,
> and the oscillator data sheet says it can drive +/-
> 16mA.
>
> Again, much thanks to the gurus.
>
> -a
>
> -----------------------------------------
> Andy Peters
> Sr Electrical Engineer
> National Optical Astronomy Observatories
> 950 N Cherry Ave
> Tucson, AZ 85719
> 520 318 8191
> apeters@noao.edu
>
> "Money is property; it is not speech."
> -- Justice John Paul Stevens
>
>
> **** To unsubscribe from si-list or si-list-digest:
> send e-mail to majordomo@silab.eng.sun.com. In the
> BODY of message put: UNSUBSCRIBE si-list or
> UNSUBSCRIBE si-list-digest, for more help, put HELP.
> si-list archives are accessible at
> http://www.qsl.net/wb6tpu
> ****
>
>

=====
Yu Wang, Ph.D
U.T. MD Anderson Cancer Center
1100 Holcombe Blvd., Box 217
Houston, TX, 77030
Tel:713-745-1671

__________________________________________________
Do You Yahoo!?
Talk to your friends online with Yahoo! Messenger.
http://im.yahoo.com

**** To unsubscribe from si-list or si-list-digest: send e-mail to majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
si-list archives are accessible at http://www.qsl.net/wb6tpu
****


About this list Date view Thread view Subject view Author view

This archive was generated by hypermail 2b29 : Thu Apr 20 2000 - 11:36:04 PDT