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XC3S50 or EPM1270?

Group, Well, I need to choose between XC3S50 and EPM1270. Both have pros and cons. I list them below, and I'd like to ask you to point out other important issues, and which would you choose if you were me.

My circuit occupies around 50% of XC3S50 or EPM1270. I might need several tens of the chips finally, But at this point I just need 1-3 for the prototype. I am aming at TQ144 package. It needs to interface 5V TTL logic. I plan to use 3.3V LVT244/245 to shift the voltage for inputs. I didn't check 5V/2.5V voltage shifters. My circuit is slow, working with 20MHz clock.

XC3S50 pros:

  • Pin compatible SC3S200 available for possible growth
  • Cheap (+ for XC3S50, + for XC3S200 at XILINX online store)
  • RAM on chip. Good if I want to add a small FIFO in the future cons:
  • Don't know where to buy XCF01S configuration flash. cost?
  • Needs both 2.5V and 3.3V power supply to interface 3.3V logic

EPM1270 pros:

  • On chip configuration flash
  • On chip user flash, if I want to store some bits in the future
  • Need only single 3.3V power supply to interface 3.3V logic cons:
  • expensive (EPM1270C5ES + at digikey). May cost more for none-ES? (for example, EPM1270C3 costs )
  • No TQ144 pin compatible bigger chips

cheers, vax, 9000

Reply to
vax, 9000
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vax,

For 5V inputs to the Spartan 3, you may also use 100 ohm series resistors from the 5V logic to the S3 inputs.

If you really want to cut costs, use a 1N4001 diode to drop the 3.3V to ~ 2.6 volts for Vccaux. Just be sure you have some reasonable value electolytic as bypass to ground on the Vccaux (like 100uF), along with the recommended bypass caps (0.01uf - 0.1uf).

The penalty of not having a perfect 2.50V voltage is that the LVDS outputs will have a few tens of millivolt higher common mode (basically, a don't care).

Aust> Group,

Reply to
austin

Hi Vax,

You will need three voltages for your S3 (1.2, 2.5, and 3.3V), while for Max II you'll need just the one (3.3V). And you won't need a seperate configuration RAM. Also, I'd look into those costs again. The EPM1270 will be in production shortly and should be cheaper longer term than low-end FPGAs such as S-3 since Max II has a smaller die.

Regards,

Paul Leventis Altera Corp.

Reply to
Paul Leventis (at home)

Thanks. I decide to go with EPM1270 because of its single power supply and on chip configuration flash.

vax, 900

Reply to
vax, 9000

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