Replacing NVSRAM chip... external battery modification possible? - Page 1
Forum section: electronics / beginners

author: Mp3
author_rank: Frequent Contributor
timestamp: July 04, 2018, 02:28:50 am
content: Hello all,This professional audio unit i'm repairing has a 1Mbit SRAM memory chip wth a battery inside the chip package to store user settings and custom programs.I have found a suitable replacement part:https://www.mouser.com/ProductDetail/Maxim-Integrated/DS1245Y-120%2B?qs=0Y9aZN%252bMVCVf6XAzbZp3eg%3D%3DBut I do not like the idea of using this, since it's not so likely this kind of memory will be available by the time it needs replacing again.I'm trying to find out if i can use a plain SRAM chip and piggyback a battery holder to the SRAM chip's pins.Would this be safe/possible? Thank you for your time.

author: AlcidePiR2
author_rank: Regular Contributor
timestamp: July 04, 2018, 03:13:11 am
content: You can dig out the battery from the old NVSRAM. Solder some wires and put an external battery holder that you glue on the chip.

author: BravoV
author_rank: Super Contributor
timestamp: July 04, 2018, 03:30:15 am
content: Quote from: Mp3 on July 04, 2018, 02:28:50 amOr use parallel FRAM, doubt you need to replace it.

author: helius
author_rank: Super Contributor
timestamp: July 04, 2018, 03:39:56 am
content: There are also SRAM devices with automatic flash backup: typically they are drop-in replacements for the battery-backed devices, but may require supply bypassing as the backup mechanism is sensitive to power glitches.

author: Mp3
author_rank: Frequent Contributor
timestamp: July 04, 2018, 04:02:56 am
content: Quote from: AlcidePiR2 on July 04, 2018, 03:13:11 amHmm. how can you safely do this without wrecking the chip?Quote from: BravoV on July 04, 2018, 03:30:15 amThat would be very cool - so far i am only finding surface mount package 128kb x 8 FRAM, but i will keep looking!Quote from: helius on July 04, 2018, 03:39:56 amI'll have to look into this as well, and good point since SRAM is quite picky about power...

author: BravoV
author_rank: Super Contributor
timestamp: July 04, 2018, 06:14:35 am
content: Quote from: Mp3 on July 04, 2018, 04:02:56 amYeah, most are SMD now days, but you can use SMD to DIP adapter, they're plenty out there, two types either fixed thru solder or detachable type that uses socket.For 128Kb x 8 FRAM, Cypress Semiconductor still manufactures it ->FM28V100

author: Gyro
author_rank: Super Contributor
timestamp: July 04, 2018, 08:41:08 am
content: QuoteA useful device for retrofit. I like the way they specify a 151year data retention, good to be precise about these things.

author: BravoV
author_rank: Super Contributor
timestamp: July 04, 2018, 09:30:31 am
content: Quote from: Gyro on July 04, 2018, 08:41:08 amLOL ... I guess Cypress Semi employs bunch of COD people especially for the datasheet dept.

author: AlcidePiR2
author_rank: Regular Contributor
timestamp: July 05, 2018, 05:36:51 am
content: Quote from: Mp3 on July 04, 2018, 04:02:56 amYou should be able to see where the chip is located. See this example.https://www.eevblog.com/forum/repair/hp-54601a-failed-checksum-test/msg548141/#msg548141

author: Leiothrix
author_rank: Regular Contributor
timestamp: July 05, 2018, 10:52:19 pm
content: Quote from: BravoV on July 04, 2018, 09:30:31 amThey employ a bunch ofOCDpeople. Or CDO people if you want the letters in alphabetical order.Sorry, I just felt irrationally compelled to post a correction

author: james_s
author_rank: Super Contributor
timestamp: July 05, 2018, 10:56:37 pm
content: I've replaced the batteries in a number of those Maxim NVRAMs, it's not the prettiest solution but it does work.FRAM is great but the DIP parts are long obsolete and hard to find, even with SMT parts it's getting a lot harder to find 5V ones, and parallel memory devices as a whole are really starting to disappear.

author: David Hess
author_rank: Super Contributor
timestamp: July 05, 2018, 11:51:44 pm
content: Quote from: Mp3 on July 04, 2018, 02:28:50 amIt is a little more complicated than that. A supervisory circuit is necessary to monitor the supply voltage and control signals like anMXD1210. In the past, a couple of diodes and CMOS gates or transistors were used for a discrete solution.FRAM is probably the best option today and usually works as a direct substitute.AutoStore nvRAM from Cypress would work if you can find a 5 volt one of the proper density but some of them require an external capacitor.