LPC MicrocontrollersのトピックRe: Low power external memory on the LPC4357

Low power external memory on the LPC4357

lpcware — Wed, 15 Jun 2016 19:53:34 GMT

Content originally posted in LPCWare by dennislumiad on Tue Jul 14 08:16:21 MST 2015
Hi all,

Currently I am working on a mobile low power pager that will be used in hospitals. To this end I have started with the LPC4357. However, it happens to be that it has not enough working memory. I have looked on the internet and came to the conclusion that either SRAM of DRAM can be used.

What i have learned is that SRAM has a lower power consumption when it not written so often. However, it is harder to make and therefore more expensive.

As about 16-32MB will be required, i thought it might be wise to go for SDRAM. I found the following: http://nl.mouser.com/ProductDetail/Alliance-Memory/AS4C16M16S-7BCN/?qs=sGAEpiMZZMti5BT4iPSEnVeWD45jS%2fiPhYe25H8%2fjPY%3d

My only concern is the energy consumption. Does anyone know how much more energy such an SDRAM memory uses compared to an SRAM; i see a lot of numbers in the datasheets but those do not really make sense to me. In principle there will be a 1200mAh battery in the pager.

Many thanks in advance for your time and consideration!

Cheers,
Dennis

Re: Low power external memory on the LPC4357

lpcware — Wed, 15 Jun 2016 19:53:35 GMT

Content originally posted in LPCWare by MarcVonWindscooting on Wed Jul 22 14:17:05 MST 2015
You shouldn't have placed this question in the 'news' forum ;-)

I have (nearly) no experience with RAM and I have no idea what a SDRAM consumes but I really doubt, that a DRAM can be low power (a few uA) because it needs refreshing (=activity).
16-32MB are an awful lot more memory that LPC4357 onboard memory!
Look at a datasheet of CY62177 for example. That one gives you numbers of power consumption in power-down/standby.

I wonder, if you really need RAM. RAM consumes power for data retention. Why not FLASH memory? Data retention for free!

Marc

Re: Low power external memory on the LPC4357

lpcware — Wed, 15 Jun 2016 19:53:36 GMT

Content originally posted in LPCWare by TinaFray on Mon Dec 21 04:38:28 MST 2015
Hello.
You can reduce the level of energy consumption up to 25% by means of read
prefetching and write combining. Moreover, reductio can be achieved even with relatively small buffers.

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Re: Low power external memory on the LPC4357

lpcware — Wed, 15 Jun 2016 19:53:37 GMT

Content originally posted in LPCWare by dennislumiad on Wed Jan 06 04:46:22 MST 2016
We went for the ISSI IS42SM16400K. They claim that is is meant for low power mobile devices. We need this because we have running a lot of stuf on the device. I.e. Wi-Fi Stack, SIP Stack, Graphical Lib, Voice calling, Echo Cancellation, Video etc :)

Thanks for pointing this out optimization opportunity; we will take this into account!