Small PROMs, EEPROMs, FRAMs, nvRAMs... are there any suppliers left today?  - Page 1
Forum section: electronics / projects

author: Benta
author_rank: Super Contributor
timestamp: July 03, 2023, 09:42:20 pm
content: I'm looking for small, non-volatile memories for complex logic decoding of some counter circuits.256 x 8 is plenty, even 64 x 4 would probably work. Larger is also OK depending on pin count and package size.Parallel address in, parallel data out (no, SPI/I2C will NOT fill my need).Access time not really critical, ~100ns or less is fineIs this kind of thing even manufactured today?And if yes, by whom? I already checked the usual suspects (Cypress/Infineon, Microchip...).

author: rsjsouza
author_rank: Super Contributor
timestamp: July 03, 2023, 09:58:01 pm
content: Mouser lists a few suppliers of 8k x 8 bit parallel interface EEPROMs.https://www.mouser.com/c/embedded-solutions/memory-data-storage/memory-ics/eeprom/?interface%20type=Parallel&memory%20size=64%20kbitWhen I was procuring some of these a while ago I could not go lower than 8k anymore, as the 2k version was discontinued by the manufacturer (and that was I2C, which has even a larger offer).If you are not looking for production but a small one-off run, perhaps Jameco can help.https://www.jameco.com/c/ICs-Semiconductors.html#/filter:ss_category:ICs$2520$2526$2520Semiconductors$253EMemory

author: PCB.Wiz
author_rank: Super Contributor
timestamp: July 03, 2023, 10:11:16 pm
content: Quote from: Benta on July 03, 2023, 09:42:20 pmNot in those specific sizes, but if you search for parallel memory, in FRAM/EEPROM/EPROM etc, and then sort by lowest price, you can still find available parts.eg Mouser show 450 parts stocked in parallel flash.Microchip still show OTP EPROM, Parallel EEPROM, Parallel Flash as in production at Microchip direct.You can also use SPLDs/CPLDs as small ROMs, the logic optimise engines reduce the product terms.

author: Benta
author_rank: Super Contributor
timestamp: July 03, 2023, 10:36:02 pm
content: OK, thanks folks.Same conclusion as mine: below 8k x 8 there's nothing there.I thought about PAL/GALs as well, but they're also on the kill list (= obsolete).

author: PCB.Wiz
author_rank: Super Contributor
timestamp: July 03, 2023, 10:49:48 pm
content: Quote from: Benta on July 03, 2023, 10:36:02 pmMicrochip still support their ATF16V8/ATF22V10 and ATF15xx CPLDs - we have units still in production using those.

author: Benta
author_rank: Super Contributor
timestamp: July 03, 2023, 11:13:45 pm
content: I know.But as my complete circuit consumes around 25 mA, I'm not going to burn 150 mA on top of that.That would require a complete power supply redesign.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: July 04, 2023, 12:33:44 am
content: Quote from: Benta on July 03, 2023, 11:13:45 pmThe 'L' family SPLDs/CPLDs we use are 5mA ballparks, and the 'Z' series are even lower. It's a rare CPLD that draws 150mA

author: MarkS
author_rank: Unknown
timestamp: July 04, 2023, 02:23:12 am
content: I went through this recently for several retro projects I have either planning or in the works. Your best bet will be to focus on flash memory and give up on the ROM idea. Not only are ROM chips terribly hard to find, but they're difficult to program. You can program a flash chip with a breadboard and Arduino Mega.Totally misread the OP and purpose. Please ignore.

author: ArdWar
author_rank: Frequent Contributor
timestamp: July 04, 2023, 02:39:13 am
content: Has anyone tested if parallel flash memory works reliably at this kind of decoder implementation. I'm cautious with this, with the usual faster bit rot and all stuffs happening with flash memory.Moving forward it's probably simpler to get away from ROM table and use CPLD however.

author: dobsonr741
author_rank: Frequent Contributor
timestamp: July 04, 2023, 02:55:32 am
content: Small EEPROM: designing in doesn't not make any sense anymore, same capacity FRAM makes more sense. If you need small storage, infrequently changed, either the MCU offers it or you can use the main flash to emulate an eeprom.FRAM, however, opens up new use cases EEPROM did not cover before: super frequently updated state storage, without any penalty. So I'm adding FM24CL16B to my RP2040 standard project template.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: July 04, 2023, 07:43:51 am
content: Quote from: Benta on July 03, 2023, 09:42:20 pmHow many bits for counter and how many bits for state-decoded outputs, and how fast does this count ?Is this a clip-on to an existing system, or do you have full design control here ?

author: fchk
author_rank: Frequent Contributor
timestamp: July 04, 2023, 09:17:12 am
content: Quote from: Benta on July 03, 2023, 09:42:20 pmToday this is a job for a small CPLD or FPGA hat contains the whole logic.Example:https://www.digikey.de/de/products/detail/lattice-semiconductor-corporation/LCMXO2-256HC-5SG32C/3232670fchk

author: mariush
author_rank: Super Contributor
timestamp: July 04, 2023, 09:25:30 am
content: Would a microcontroller be fast enough to be used as a fake eeprom? Because you could get some 24-40 pin micro and have some interrupt on change on a port (8 input bits) or 10-12 bits and have the program instantly set the output to some ram stored value.or maybe use parallel SRAM and load the data into the SRAM at boot using a cheap micro? I see 256 kbit SRAM for half a dollar on Digikey

author: Hawaka
author_rank: Regular Contributor
timestamp: July 04, 2023, 09:39:08 am
content: Quote from: fchk on July 04, 2023, 09:17:12 amIf all you want can be done in logic gate, then a CPLD would be a great choice. I have used in the past some Xilinx XC2C with great success. Not expensive, easily programmable.

author: nctnico
author_rank: Super Contributor
timestamp: July 04, 2023, 12:01:17 pm
content: Quote from: Benta on July 03, 2023, 09:42:20 pmI'd go for one of the small FPGAs from Gowin. Very easy to use and their SPI programming algorithm is super simple to implement yourself.

author: Benta
author_rank: Super Contributor
timestamp: July 04, 2023, 09:54:07 pm
content: Thanks for all your suggestions.I have a limitation that wasn't mentioned in my first post:The circuit is an addition to an existing 5 V CMOS-level system, and I have a power budget.Using standard 74HC parts plus a decoder circuit (the PROM) would be the optimal solution, price/power/sizewise etc.Concerning CPLD/FPGA solutions, believe me, I've trawled the net for suitable devices.The 5 V offering is miniscule, and burns power like there's no tomorrow.Choosing lower-voltage devices with "5 V tolerant I/O" (misnomer, it only applies to the inputs) widens the field, but then I need to add translators for the outputs plus additional voltage regulation. Nothing saved, but higher power.A 5 V, CMOS 22V10 would probably do the job, but they're also extinct.So, I'm back to standard 74HC logic again.Oh, well...

author: PCB.Wiz
author_rank: Super Contributor
timestamp: July 04, 2023, 11:49:35 pm
content: Quote from: Benta on July 04, 2023, 09:54:07 pmYou need ATF22V10CQZ or ATF22LV10CQZ, or if those are not enough, ATF750CL, or ATF1502ASL/ASVL or ATF1504ASL/ASVLMicrochip even show stock of ATF22LV10CQZ-30PU 3uA static Icc, ~ 2mA/MHz below 7.5MHz

author: Benta
author_rank: Super Contributor
timestamp: July 05, 2023, 12:07:57 am
content: Quote from: PCB.Wiz on July 04, 2023, 11:49:35 pmUmm, no.Those are as power-hungry as all the others, and can't drive CMOS inputs. A no-starter.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: July 05, 2023, 12:29:29 am
content: Quote from: Benta on July 05, 2023, 12:07:57 amYou need ATF22V10CQZor ATF22LV10CQZ, those suffix letters matter.

author: Benta
author_rank: Super Contributor
timestamp: July 05, 2023, 12:46:33 am
content: Quote from: PCB.Wiz on July 05, 2023, 12:29:29 amYou're right, missed that. Unusual place for power options, normally that's where package coding goes.Never mind.So those devices will "only" burn off ~20 mA?That's what the full circuit consumes in total (using 74HC + opamps + references etc.), so that one device will add that on top?I'm underwhelmed with the PLD/CPLD offering these days.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: July 05, 2023, 01:10:15 am
content: Quote from: Benta on July 05, 2023, 12:46:33 amNope, that Icc is entirely dependent on clock speed. How fast is this actually clocking ?Quote from: Benta on July 05, 2023, 12:46:33 amYes, they are seen as trailing edge, and I see Xilinx are quietly hiking the prices of their XC2C CPLD parts, which just makes them even more trialing edge.Microchip/Atmel actually have a quite nice ATF1502BE / ATF1504BE low Icc offering, but they keep it close to their chest. Still shows as active production.let's compare:XC2C32A-6VQG44C IC CPLD 32MC 5.5NS 44VQFP 1,000 : $5.11000ATF1502BE-7AU44 32 MC CPLD,1.8V ISP CPLD,44 PIN TQFP 1000-4999* $2.19I'm not sure how 'real' these are but octopart link to this : Availability: 2,935 pieces 1+ $1.55 1000+ 1.43https://www.augswan.com/pdut/ATF1502BE/6937175.htmYou can buy XC2C64A boards from Aliexpress for less than the part-list prices on Digikey etc

author: PCB.Wiz
author_rank: Super Contributor
timestamp: July 05, 2023, 01:27:50 am
content: Quote from: mariush on July 04, 2023, 09:25:30 amYes, if speed mattered here, SRAM loaded from a cheap MCU would be faster and cheaper than flash/eeprom solutions.

author: ArdWar
author_rank: Frequent Contributor
timestamp: July 05, 2023, 03:23:34 am
content: If they're that bothered with 20mA part, using SRAM won't help either.At what point converting the entire (internal) logic circuitry into 3v3/2v5 LVC and only using 5v HCT as last output stage start making sense?

author: PCB.Wiz
author_rank: Super Contributor
timestamp: July 05, 2023, 03:32:01 am
content: Quote from: ArdWar on July 05, 2023, 03:23:34 amSRAM parts have low static Icc, (usually some uA) so the actual Icc here depends entirely on the (still not provided) actual operating speed.

author: Benta
author_rank: Super Contributor
timestamp: July 05, 2023, 11:44:02 pm
content: Quote from: PCB.Wiz on July 05, 2023, 03:32:01 amit's just around 1 MHz (as indicated in the original post looking for 100 ns access times).But I've solved it in the meantime using analog multiplexers creatively (4051 types). At less than 1 mA current consumption, full 5 V CMOS compatibility and cost point around a dollar total.Thanks for your feedback and suggestions.