# Why limits on MicroSD sizes? **URL:** \ **Category:** Factual Questions\ **Created:** [June 30, 2019, 11:20pm UTC](https://boards.straightdope.com/t/why-limits-on-microsd-sizes/836314 "2019-06-30T23:20:04Z")\ **Posts on this page:** 6\ **Page:** 2
**Author:** ![Cleophus](https://avatars.discourse-cdn.com/v4/letter/c/a88e57/32.png) [@Cleophus](https://boards.straightdope.com/u/Cleophus)\ **Post date:** [July 4, 2019, 4:24am UTC](https://boards.straightdope.com/t/why-limits-on-microsd-sizes/836314/21 "2019-07-04T04:24:10Z")
> [@anomalous1](#): > > No, not nonsense. > > If there is a card reader designed for handling up to a certain capacity, it will have differences in how much voltage and current is able to be delivered from a new one that can write larger amounts. It is stored in these chips in solid state/ flash memory. If this is about magnetism, my apologies, it’s easier to describe that than saying “tiny cores holding an electric charges or voltage” > > I know I quipped in the pit about how I hate citations, but here is a reliable and quick one; [https://www.reference.com/technology/sd-cards-work-befa4e0fdedcc835](https://www.reference.com/technology/sd-cards-work-befa4e0fdedcc835) It will not. That’s not how the card reader works. The flash controller is internal to the SD card itself, which is where all the things you linked to are handled and are how all flash memory works, not just SD cards. SD cards use 1.8 V and 3.3 V regardless of capacity. ---
**Author:** ![Great\_Antibob](https://avatars.discourse-cdn.com/v4/letter/g/e47c2d/32.png) [@Great\_Antibob](https://boards.straightdope.com/u/Great_Antibob)\ **Post date:** [July 4, 2019, 4:37am UTC](https://boards.straightdope.com/t/why-limits-on-microsd-sizes/836314/22 "2019-07-04T04:37:00Z")
> [@anomalous1](#): > > No, not nonsense. Yes, nonsense. You posted something about voltage, which isn’t exactly _wrong_ but it’s definitely not relevant. All SD cards will be supported by the same voltage. If voltage were a factor, you couldn’t simply swap out cards of a different capacities as easily as we do. In fact, that’s a feature. We don’t want voltage to be a factor, so SD cards are designed so they are not a factor. As mentioned above, if a device supports a certain SD card type (SD, SDHC, SDXC, etc), it should hopefully support all cards of that type regardless of data capacity. This may not always be the case, but that will have nothing to do with voltage, current, or magnetism. It will rather almost certainly be due to hardware or software issues as the engineers may not have designed the device properly for the standard. Or, in many cases (and quite possibly in this case), the device is properly designed but was never tested for newer SD cards and they do not want to guarantee it will work in a situation that was never adequately tested. You can get lawsuits that way. It’s ok to hazard a guess, but doubling down with an irrelevant citation (the website you cite doesn’t say anything relevant about voltages or current or why that would mean certain cards wouldn’t work) doesn’t help somebody making a potentially expensive purchase. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [July 4, 2019, 4:56am UTC](https://boards.straightdope.com/t/why-limits-on-microsd-sizes/836314/23 "2019-07-04T04:56:32Z")
In the very early days of digital cameras (~1996) there were 3.3V and 5.0V versions of SmartMedia cards. Those were not compatible with each other. But I haven’t seen any voltage compatibility issues since then. SmartMedia was a special case anyway, they were basically raw memory chips with no onboard controller chip. All other removable memory cards have onboard controller chips. ---
**Author:** ![markn\_1](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@markn\_1](https://boards.straightdope.com/u/markn_1)\ **Post date:** [July 4, 2019, 3:11pm UTC](https://boards.straightdope.com/t/why-limits-on-microsd-sizes/836314/24 "2019-07-04T15:11:06Z")
Here is an overview of the SD card specs from the SD Association: [SD Standard Overview | SD Association](https://www.sdcard.org/developers/overview/index.html). As noted, the voltage is identical for all SD and microSD cards: 3.3V in the first row pins and 1.8V in the second row. ---
**Author:** ![anomalous1](https://avatars.discourse-cdn.com/v4/letter/a/e56c9b/32.png) [@anomalous1](https://boards.straightdope.com/u/anomalous1)\ **Post date:** [July 4, 2019, 8:26pm UTC](https://boards.straightdope.com/t/why-limits-on-microsd-sizes/836314/25 "2019-07-04T20:26:31Z")
> [@Great\_Antibob](#): > > Yes, nonsense. > > You posted something about voltage, which isn’t exactly _wrong_ but it’s definitely not relevant. > > All SD cards will be supported by the same voltage. If voltage were a factor, you couldn’t simply swap out cards of a different capacities as easily as we do. In fact, that’s a feature. We don’t want voltage to be a factor, so SD cards are designed so they are not a factor. > > As mentioned above, if a device supports a certain SD card type (SD, SDHC, SDXC, etc), it should hopefully support all cards of that type regardless of data capacity. > > This may not always be the case, but that will have nothing to do with voltage, current, or magnetism. It will rather almost certainly be due to hardware or software issues as the engineers may not have designed the device properly for the standard. > > Or, in many cases (and quite possibly in this case), the device is properly designed but was never tested for newer SD cards and they do not want to guarantee it will work in a situation that was never adequately tested. You can get lawsuits that way. > > It’s ok to hazard a guess, but doubling down with an irrelevant citation (the website you cite doesn’t say anything relevant about voltages or current or why that would mean certain cards wouldn’t work) doesn’t help somebody making a potentially expensive purchase. Absolutely was hazarding a guess, though now I believe I was thinking of a different type of storage media. I only put that “cite” down to show that variable voltage is definitely involved. Thanks for the correction. I stand corrected, perhaps I was thinking of older card readers. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [July 5, 2019, 12:52pm UTC](https://boards.straightdope.com/t/why-limits-on-microsd-sizes/836314/26 "2019-07-05T12:52:26Z")
I would like to remind people that it isn’t easy to provide a steady voltage to a variety of things with different demands on current draw. So you’re making a digital camera. You’re trying to conserve battery life. You test a bunch of then available SD cards to find out how much they draw. You design the circuit accordingly. Then new, higher capacity and/or faster, SD cards come along. In addition to maybe not being able to handle the new capacity or speed the circuit in the camera might not be able to provide enough power to read/write the card and keep the voltage stable. (There’s been some exciting developments in power supplies btw. The new [gallium nitride](https://www.google.com/search?q=gallium+nitride+power+supplies) chips make them smaller and more efficient. Gallium arsenide has always been full of promise but never made it big. Maybe this is the camel’s nose to a new era of solid state devices.) [Previous page](https://boards.straightdope.com/t/why-limits-on-microsd-sizes/836314.md?page=1)