Why MMA9555 's Pin1 ID is shortened to Pin1?

[wenxue]

Hi everybody,

I found MMA9555's Pin1 ID is shortened to Pin1. Actually the resistor between them is 0.3Ω. Do you know what's the reason?

I don't find any description about Pin1 ID in datasheet. Generally speeking, this pin should be just an identification. I don't understand why it connect to VDD.

Any comments would be appreciated.

[JackITB · Accepted solution]

Hi Wenxue,

This is due to the layout of device package substrate: pin 1 ID is connected to pin 1 through the bottom layer of this LGA substrate.

Datasheet provides footprint and land pattern information which keep pin 1 ID unconnected. Did you experienced any issue when mounting the part ?

Regards,     Jacques.

[wenxue]

Hi Jacques,

Yes, a customer meet an issue when mounting the part. Customer designed a pad in the bottom of the chip, and the pad is connected to GND. So Pin1 VDD is shortened to GND in this case.

Datasheet don’t have any information indicate Pin1 ID is shortened to GND. I think we need describe it clearly.

Best Regards,

Wenxue

[JackITB]

Hi Wenxue,

I'm surprised the customer introduced a GND pad under the package.

Figure 14 and 13 in Datasheet are providing clear description of solder mask and stencil opening.

Anyway, we'll add a word of caution about pin 1 ID in a subsequent revision of the datasheet.

Thanks for raising this concern,     Jacques.