Don Scansen published his Apple iPod Touch camera module thoughts in
SemiSerious blog. The module uses Micron MT9D112 2MP camera-on-a-chip. Naturally, Don gives its die photo by Semiconductor Insight. One can see a heavy price Micron pays in chip area for ISP integration:
What do you mean by heavy price? Seems to me they have captured the sale of both image sensor silicon and ISP silicon. The customer wins due to smaller camera package and better reliability. Interconnect engineering also benefits from the close proximity.
ReplyDelete-EF
The alternative is having ISP on the application processor. In comparison with image sensor, application processor typically uses more advanced process, may be 65nm vs 130nm in image sensor. Also, image sensor typically has no more than 4 metal layers, this increases ISP portion routing.
ReplyDeleteAlso, to maintain a low sensor noise, the ISP and sensor portions are operating in separate time slots. This complicates the ISP design, given the high throughput it has to provide in less time.
Last, the yield of image sensor is typically lower than one of application processor. So any additional piece of area on sensor is subject to the yield loss because of sensor portion. Thus a part of "good" ISPs are thrown out. Quite cosltly.
Yes, this discussion has been going on for, well, as long as the camera on a chip has existed.
ReplyDeleteBut, you said Micron was paying a heavy price. Maybe you meant Apple was paying a heavy price to enjoy the benefits of integration?
But, one would expect this in such a leading edge, compact product, no?
The last thing this community needs is for image sensors to become a commodity product. Product differentiation through improved functionality is one of the ways to fight that.
In my mind, the Micron 2MP SOC is a shining example of realizing the potential of CMOS image sensors.
-EF
You are right, it's Apple paying the high price here. SOC solution does not require much effort to put it in the iPhone or iPod. If Apple go for a separate solution, it would need quite a lot of time to optimize its ISP setup, or hire Sasken or whoever else familiar with Micron imagers integration.
ReplyDeleteWorse, many stand-alone ISP design houses do not understand modern sensor artifacts, so their ISP hardware just can not do a good job.
Ideally, the separate ISP solution should cost less, but with all the real world limitations SOC is more popular probably.