Choosing package for STM32H743 SPI HS - BGA or LQFP ?

[cipek]

Hi,

I'm interfacing external ADC - 16 bit, 10MSPS (AD7626) with this microcontroller. STM32 SPI will work in slave mode, ADC will provide 80MHz clock. It will work in a burst mode - sampling 288 measurements x 16 bits at 5MHz.

I can't decide whether I need BGA for this or LQFP will be sufficient. I remember having issues with internal ADC under performing when used in LQFP package. I don't want to go with BGA unless I have to.

Cheers

[AScha.3]

@MasterT 

>I have hard time to comprehend theirs DS.

Right, compared to STM ds its ... sometimes bit strange. :)

+

>CNV to Last CLK (LSB) Delay 72 ns max 

this is for doing very fast conversions, if giving next CNV very early -> the min time needed, between CNV to last bit of previous conversion.

@cipek 

So i see no problem running at 80M spi clk, with 16bits = clocks per sample , 80/16 -> 5 Msps , also in LQFP .

BUT : how you generate the 20ns CNV "start" pulse, followed by 100ns waiting, then transfer SPI 16 bits ?

You need special hardware for this....maybe a TIM , generating the cnv start pulses, 20ns hi, 180ns lo ;

then a 100ns delay (R-C and a cmos gate or other timer), then starting the SPI (at 5msps-> 200ns, -100ns delay until MSB , then 100+72= max. 172ns time for 16bits, so min. 93 MHz clk for SPI needed; seems 100M is your friend, to have some space/gap remaining.

[cipek]

I was planning on using the timers to do that. But I have to check if I have enough of the timers, as I already use some to generate some required signals for other devices. Well, it's getting trickier than I thought it would be...

Thanks for all the tips!