5V CPLD? - Page 1
Forum section: electronics / general

author: ajcrm125
author_rank: Contributor
timestamp: January 24, 2021, 05:43:58 pm
content: Looking to use a CPLD capable of driving 5V. Lattice seems to have some legacy stuff (ispMACH 4A5)but the software required to program them costs a minimum of $500+. Any other comprarable devices out there or should I just look into using 3.3V devices and some level shifters?Thx!-Adam

author: asmi
author_rank: Super Contributor
timestamp: January 24, 2021, 09:43:02 pm
content: For anything other than one-offs, I would go with a more modern device and level shifters. Because legacy devices can disappear from stock forever at any moment, leaving your design in a limbo and forcing you to switch to more modern device + level shifters anyway, but this time under immense time pressure and with angry customers if revised version will not work exactly like old one did and/or if it will be more expensive than the old one.

author: oPossum
author_rank: Super Contributor
timestamp: January 24, 2021, 09:51:18 pm
content: There are a few 5V devices available from Microchip (formerly Atmel).https://www.microchip.com/ParamChartSearch/chart.aspx?branchID=30024

author: fabiodl
author_rank: Frequent Contributor
timestamp: January 25, 2021, 12:13:50 am
content: Have a look at lattice ispmach series. Be prepared to deal with awful software though.

author: dolbeau
author_rank: Regular Contributor
timestamp: January 25, 2021, 07:57:08 am
content: Quote from: ajcrm125 on January 24, 2021, 05:43:58 pmDo you need the full 5V or to talk to something that goes up to 5V? I had a similar question not too long ago in this forum, when I wanted to interface a 3.3V FPGA with a legacy 5V bus:Suitability of/alternative to TXS0108EPW for 5V <-> 3V3 level shifting @ 25 MHz. Thanks to the explanations I got in that thread, I ultimately went with SN74CB3T16211 switches and they work just fine in the vintage hardware (https://github.com/rdolbeau/SBusFPGA).

author: mon2
author_rank: Frequent Contributor
timestamp: January 25, 2021, 07:07:36 pm
content: On the TXS devices from TI.DO NOT use them for any long cable drive. Been there, done that, killed too many hair follicles in the process. At the end of a 8ft or so cable (IEEE1284) drive the text book perfect square wave looked like something my son could use for his toboggan. Even though TI FAE stated it should be fine. Waste of life and not a happy owner of a almost full T&R of the components.Ok for short PCB traces but watch out for the recommended external pull-ups which may impact your other mated logic.Do you require the logic levels to be bidirectional?Do you have a DIRECTION pin to select if in output or respectively input mode for this traffic?How many bits?You are only wanting to OUTPUT @ 5 volt swing?There are other solutions but need more data.

author: Bassman59
author_rank: Super Contributor
timestamp: January 25, 2021, 09:03:20 pm
content: Quote from: ajcrm125 on January 24, 2021, 05:43:58 pmXilinx XC9500 (not the XL), but Xilinx has them labeled obsolete.Use level shifters.

author: mon2
author_rank: Frequent Contributor
timestamp: January 26, 2021, 03:31:31 am
content: How complex is your CPLD?Have a look at the devices from Silego.They have devices that can operate and swing at 5 volts.

author: james_s
author_rank: Super Contributor
timestamp: January 26, 2021, 07:24:35 am
content: In most cases I've found it works just fine to drive 5V logic with 3.3V logic. Going the other way around you have to be careful but in hobby projects I've gotten away with just putting a resistor in series with the input to limit the current and relying on the protection diodes in the CPLD.

author: Berni
author_rank: Super Contributor
timestamp: January 26, 2021, 08:07:05 am
content: Yep you can cheat 5V by just using series resistor to limit the current into the pin.But there are also CPLDs out there that are "5V tolerant". For example the rather modern Altera MAX V series is one of them. This means that the IO supply voltage is still limited to a max of 3.3V, but the ESD diodes are changed to clamp slightly above 5V. This means that a 5V signal can be fed into a input pin without any issues.For output of 5V on these it depends what you drive. The 3.3V output can directly drive TTL input logic since its above the 2V threshold. For CMOS it doesn't hit the typical 80% of Vcc, so in that case you can put a pullup resistor to 5V on that pin, then you just tristate the pin when you want it high and the pullup will get it to 5V.This means you only need level shifters if you need to output 5V into something that draws like 10mA of current and that is pretty rare.

author: bingo600
author_rank: Super Contributor
timestamp: January 30, 2021, 06:52:52 am
content: Quote from: oPossum on January 24, 2021, 09:51:18 pmVerilog on the ATF1508http://avitech.com.au/?page_id=3195Seems like the Atmel is like an Altera 7xxx , and Quartus 13.0(SP1)Can generate bitstreams for it , you'd have to use an Atmel programmer though.Seems like an Altera ByteBlaster or ByteblasterMV can do it too , but requires a Par-Port on the pcwww.mikrocontroller.net/attachment/21516/QSTutor.pdfhttps://www.instructables.com/Ghetto-Programmable-Logic-CPLD-Development-Syste/But the Atmal cable isn't that expensivehttps://www.kanda.com/CPLD-Programmers.175.html/Bingo

author: TomS_
author_rank: Frequent Contributor
timestamp: February 07, 2021, 02:52:49 pm
content: The Atmel 5V parts are still in active production, so are possibly a better bet in terms of being able to source them from reputable places. They also come in 3V3 versions.Theres an active project at the moment to figure out the internals of the ATF150x series, so probably some time in the not too distant future there will be open source toolchains to work with these devices.https://whitequark.github.io/prjbureau/I believe they have more or less completed the 1502, and the 1504 and 1508 are partially done.Otherwise, for the time being your options are:* Learn CUPL and use WinCUPL, which is .. fun (personally, I enjoy it)* Use an older version of Altera Quartus that supports the EPM7000 series devices, since these are pin compatible with ATF150x's, and a tool called pof2jed to conver the Quartus output to a JED file for pgramming via ATMISPEPM7032 = ATF1502EPM7064 = ATF1504EPM7128 = ATF1508

author: Bruce Abbott
author_rank: Frequent Contributor
timestamp: February 09, 2021, 08:49:17 am
content: Quote from: mon2 on January 25, 2021, 07:07:36 pmThat will be a problem even with many ancient '5V' CPLDs, and GALs too. Most only guarantee 2.4V high output.

author: jmelson
author_rank: Super Contributor
timestamp: February 15, 2021, 10:22:52 pm
content: Quote from: Bassman59 on January 25, 2021, 09:03:20 pmXC9500 have not been available for about a decade. The 9500XL series are 5V tolerant, and still in production. The outputs are TTL compatible, and can be pulled up to 5 V with a resistor. But, if the OP really needs a 5V swing, then the level shifter is the way to go.Jon