I don't know about SD being cheaper.  You have to consider the socket
when you chose to go with an external media such as SD or even Compact
flash, which is an even cheaper media than SD.

I would find a different memory package.  Chips come in all sizes and
flavors.



Herbert Graf wrote:
>>Hello all,
>>          I'm haing a problem figuring out the best (cheapest) way to
>>store 1024k x 8 (8Mb) of data for a battery powered data logging
>>application.  The data doesn't have to be retained on power loss.
>>
>>I thought the best way to do this would be to use one of the following
>>SRAM chips:
>>http://www.cypress.com/cfuploads/img/products/CY62158CV33LL-70BAI.pdf
>>
>>http://www.samsung.com/Products/Semiconductor/SRAM/LowPower/LowPow
>>er_n_LowVoltage/8Mbit/K6X8008T2B/ds_k6x8008t2b.pdf
>>
>>The application is battery powered and suppose to be small so I don't
>>care for the second chip much as it seems to be hard to find, very
>>power hungry while operating and a larger package then the first.
>>
>>The first chip is excellent, however it's a FBGA and a very small one
>>at that. So I'm really not sure how I can make a PCB for this with our
>>standard board house 6mil space/6mil trace.  If I put vias under each
>>pad the vias will be too big for the pins (my board house's smallest
>>via is .35mm and the ball diameter is .3mm).  How is mounting of FPGAs
>>typically done?  Can I put a pad under each outside pin then use vias
>>in the middle and count on the solder paste on joining the balls to the
>>vias?  Doesn't seem like a good idea, since the ball will not toush the
>>via and I'm counting on the solder paste to bridge the gap when it
>>melts.
>>
>>OR is there a cheaper way to store all my data than SRAM?
>
>
>         I don't know about cheaper, how many do you plan to make? You could always
> go with an SD Flash card. They're quite small, easy to interface to and can
> be very cheap in small quantities. TTYL
>
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