interesting FIFO chips
Fred Hawkins
Posts: 997
Poking around (ie lost) TI's website, I ran across their FIFO memory chips.·Which seem to be well suited for ADC/DAC·problems with·the prop or data streams with·too much·too fast for the prop to cope with.
They are not particularly cheap nor small·-- the biggest is a 128 pin qfn,·with a digikey price for one was·$29.
But they do run at up to 166 Mhz, and will hold 32k x 36 bits. They can remap the wordsize to the 18 bits and I·think 9 bits, as well as swap endiness.
They have separate pins for the i/o and are tailored for circular buffers.
There are also ones that are smaller in width (18 bits). One of them is 64k x 18:·SN74V293
http://www.ti.com/sc/docs/products/fifo/dspsync_fifo.htm
·
They are not particularly cheap nor small·-- the biggest is a 128 pin qfn,·with a digikey price for one was·$29.
But they do run at up to 166 Mhz, and will hold 32k x 36 bits. They can remap the wordsize to the 18 bits and I·think 9 bits, as well as swap endiness.
They have separate pins for the i/o and are tailored for circular buffers.
There are also ones that are smaller in width (18 bits). One of them is 64k x 18:·SN74V293
http://www.ti.com/sc/docs/products/fifo/dspsync_fifo.htm
·
Comments
I managed to get 2 MSPS with a 8 bit ADC directly couled to the prop... no problem, but more... it gets complicated. Again, the input circuit is the tricky art of low noise high-speed electronics (unknown to me).
29 is not that much, if you get a 166 MSPS (or 150) or 300 with two ADCs. ADCs in those regions carry 2 sets of outputs to divide bandwidth... so you could sample at 300 MHz with two channels
I'd not know if my PCB desing skills are good enough for such freqs, and as I said... how about some fast OAs... together with the ADCs cost quite a bit.
But again, displaying the info in a big 512x384 monitor with the prop is kids' work (well is not that easy, but it is already done, and works),
But·why not to begin playing with the TLC5540 from Texas Instruments, you can search at the TI site for that, it's a 40MSPS flash parallel 8 bit ADC, and they sell the demo boards for that, it's cheap...I bought some·of them with only a $30.- of shippent (not customs fee because they are for education, etc.).
·With the board made...you avoid the PCB problems, unless in the ADC part...then trying with a four layer board for the FIFO could be not so hard.
I think it's good to learn more, and maybe usefull for some application managing video, talking about osciloscope....could be suitable for audio applications.
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Regards.
Alberto.