VDDSDMMC AND VDDUSB Clarficiation

[Kishan Joshi]

SO i was doing some stm32 research and developed some application now i am going in production phase. Now i wanted to use stm32f765 but there are couple of variants in that series.

I am getting confused between this two models STM32F765ZIT6 and STM32F765VIT6 so the basic confusion comes from vddsdmmc and vddusb . this two pins are available in Z series while its not available in V Series. Since sdmmc and usb is supported in both the soc. Then why is it not available on V series .

Since i am not getting enough information from reference hardware design regarding vddusb and vddsdmmc. If there is any specific improvement which is vddusb and vddsdmmc is responsible then i want to use Z series other wise i don't want to have any burden on pcb by just increasing pin numbers and i will go ahead with v series

Thank you! Please help

[Tesla DeLorean]

Does your design run at a low voltage? Or at 3.0 to 3.3V?

Does it use USB connectivity?

To meet USB specifications for signalling the transistors need to be powered at specific minimum levels.

The chips share a common die, it is bonded out differently depending on the package. These absent pins are bonded to a nearby VDD pin for the purpose of powering specific pin drivers.​

[Kishan Joshi]

no my application is not low power system. it is flight controller so power is not an issue. and it is working on 3.3v. first i choose stm32f765 but later when i started making schematic then i got confusion about vddsdmmc and vddusb since it is not available in v series i got confused that if these features are available or not in the v series. they should have mentnion these things in the datasheet. 

Yes i want to use USB. but if there is not vddusb on v series will usb work ?

[TDK · Accepted solution]

I would assume if these pins are absent, they are bonded to VDD internally. I looked for this statement in the datasheet but didn't find it stated explicitly. Since you're running at 3.3V, that means you can use SDMMC/USB without issue.

[Tesla DeLorean]

Like I said it is bonded to a nearby VDD on lower pin count packages, the USB pin drivers will use that, and as it is at a sufficiently high voltage the pins will meet specifications.

>> they should have mention these things in the datasheet. 

You need to do a better job at reading, and interpreting the datasheet.

VDDUSB can be connected either to VDD or an external independent power supply (3.0 to 3.6V) for USB transceivers (refer to Figure 4 and Figure 5). For example, when the device is powered at 1.8V, an independent power supply 3.3V can be connected to VDDUSB.

The pitfall here is if you're running down at 2.0 or 2.7V the USB isn't going to function reliably on the low pin count packages.

[Kishan Joshi]

Thank you sir it has been amazing that ar forum is very helpful regarding development.

Thank you sir so much​

[Kishan Joshi]

Yes sir, in L series datasheet they have clearly mentioned that vdd is connected internally. But in F7 it is really hard to interpret. Thank you for pointing out the mistake. Yes i got it. It is written indirectly. Thank you​