Forum Discussion
Honored Contributor2.5V AS serial configuration device?
I'm finising off a spin of a board and trying to move from VCCIO of 3.3V to 2.5V. We're pin constrained so I'm moving the banks with the configuration pins too.
I'm using active serial config and can't find an EPCS16 equivalent that works down to 2.5V. My friendly apps guy has pointed me to some NXP level translators but space is reasonably tight and I'd prefer to do without these if I can. I presume Quartus still checks the device ID and balks if it doesn't think it's an EPCSXXX? (Altera, can you stop this?). Has anyone got a good solution for... EPCS16 compatible. 2.5V operation. Thanks for any pointers, Nial.13 Replies
Altera_Forumi've used Atmel parts that support 2.5V without a problem
- Altera_Forum
Thanks TPC,
Do you have any pointers to an example device or family to narrow the search (I'm about to head out so will look later). Nial - Altera_Forum
AT25DF041A-SSHF-B
make sure you get the 50 MHz part which supports 2.5V - Altera_Forum
Unfortunately the EPCS16 equivalent doesn't seem to come in a 2.5V part.
I've had a quick check through Digikey and can't see any other alternatives. Any further pointers really appreciated. Nial. - Altera_Forum
how about this one:
AT45DB161D-SU-2.5 - Altera_Forum
What if you use this spansion part:
S25FL128P0XNF http://www.spansion.com/support/datasheets/s25fl128p_00.pdf And run it at 2.7V. The IOs on the FPGA should be able to talk to it. - Altera_Forum
Why using a a 2.5V device at all ? If you still have a 3.3V rail on your board you can power the ECPS16 with 3.3V and directly connect it to the pins on the 2.5 I/O bank. The only thing you have to do is to disable the clamping diode and control your overshoots. This is what application note 447 says. The only problem I see is the small margin for the input high level on the EPCS device (VCC*0.6). Maybe you can reduce the power supply for the EPCS16 device to 3.0V.
Regards, HJS - Altera_Forum
Thanks for the suggestions guys.
--- Quote Start --- how about this one: AT45DB161D-SU-2.5 --- Quote End --- That doesn't have the legacy 'read device ID' command that should return 0x14 for an EPCS16 equivalent. Having said that I'm not sure if that's a problem with indirect programming and a *.jic that we're using. Anybody know if this is required? --- Quote Start --- Why using a a 2.5V device at all ? If you still have a 3.3V rail on your board you can power the ECPS16 with 3.3V --- Quote End --- Most of the data sheets I have checked state VInHigh is Vcc * 0.7 so the guaranteed 2.5V output of 2.0V isn't high enough. The simplest/ cheapest solution looks like it's going to be to use a small dedicated voltage regulator to power the config device at ~2.8V. Thanks again, Nial. - Altera_Forum
my reasoning was to have only 2 rails, 2.5V and 1.2V
- Altera_Forum--- Quote Start --- my reasoning was to have only 2 rails, 2.5V and 1.2V --- Quote End --- I would have preferred that. I have had problems in the past where I was trying to program a device directly from Quartus and it didn't have the same device ID as the EPCSX it was replacing. When Quartus didn't get the device it was expecting it stopped. I'm using *.jic indirect programming and don't know if this is still a problem or not but until I know for sure I am going to play safe. Have you used these alternative devices (that don't support the legacy read device ID instruction)? Nial
