Performing a Tear Down on the Samsung TL225 digital camera revealed how they kept the BOM under control while expanding on the features.
By Richard Nass
Embedded.com (12/10/09, 09:47:00 AM EST)
It must be difficult for digital still camera vendors to differentiate their products from those of competitors, at least in the eyes of consumers. They can compete on resolution, battery life, image quality, etc. But those features are hard for the consumer to visualize, at least while in the store making a purchase. When you can come up with something that's truly different, then you have something you can really sink your marketing teeth into.
That's what the designers at Samsung have come up with—a digital still camera with a truly differentiating feature. The TL225, which happens to be the object of my current Tear Down, is built with a secondary display. It has the usual 3.5-in. display on the back. But the key is that it has a secondary display, measuring 1.5-in., on the front side of the camera.
The Samsung TL225 digital camera offers a differentiating feature—a secondary display on the front side of the camera.
If you're a 40-something like me, you may question why there's a display on the front of the camera. But show that camera to one of your kids like I did, and they know exactly what it's for—to take a picture of yourself or you and your buddies together.
The key for Samsung was to not raise the BOM much beyond what's required for a single-display camera. And they seem to have achieved that. Taking the camera apart showed that there are two key ICs on the board in addition to the memory.
Samsung was able to keep the BOM to a minimum by keeping the number of components to a minimum.
The Coach 10 device, from Zoran, drives the main display and also handles all the data conversion for the secondary display. In essence, the IC is connected to the image sensor on one side and the LCD on the other side. In between is the interface to the flash memory. The part corrects for image stabilization, lighting, and barrel effect, both in still mode and high-definition video mode.
Zoran claims to offer more than just the silicon. They provide many of the necessary algorithms, and even a reference platform that's pretty close to everything an OEM needs to go to market with a finished product. The Coach 10 also appears in Cisco's Flip UltraHD digital camcorder, which we took apart a few months ago.Note that Zoran has since released the next two devices in the Coach family, the 11 and 12. Those parts add features like face tracking, blur correction, noise reduction, and real-time lens distortion compensation.
The second part on the board is an Igloo AGL060 device from Actel, measuring 6 mm on a side. It's a flash-based FPGA that consumes very little power, operating down to 1.2 V. This particular part contains 60,000 gates and 96 user I/Os.
The Igloo FPGA is responsible for two key functions. One is to manage the interface between the Zoran part and the memory. And the second is to handle the interface to the secondary display. Hence, it's responsible for the LCD timing control and video downscaling.
The Igloo probably could have reduced some of the processing burden in the Zoran processor, had the Samsung designers chosen to do that. While that may have allowed for a slightly less powerful main processor, it would have required a lager die for the FPGA. That's an architectural decision the system engineer has to make. But the guess here is that they likely could have reduced both the bill-of-materials (BOM) and the power consumption slightly.
One of the nice features of the Igloo is that it can operate as either the master or the slave for power control. With a feature called Flash Freeze, the device goes into a very low power mode, around 10 μW. In this state, even though there's no logic toggling, I/Os can still be receiving data. But there's no power being consumed at the I/O or core level. Because the FPGA is flash-based, the value of the registers (or the memory itself) is not lost. Externally, there's no need to switch off the power, or gate or turn off the clock.
The software development for the camera was a designed mostly by Samsung, with drivers coming from Zoran and Actel. That makes the integration and validation a little tricky, because at the end of the day, or the end of the design in this case, all the pieces have to fit together, especially in terms of the timing and I/O assignments. Hence, there's a lot of finger crossing when you get to the validation stage. But in the case of the TL225, it's obvious that they got everything worked out, as the camera shipped on schedule.
On such a system, overall system validation could be difficult, in terms of developing pieces of code, making sure the timing and I/O assignments are accurate. You also have to make sure the footprint is right in terms of having everything fit properly on the board. I know that sounds obvious, but it should not be taken for granted.
Keeping the footprint as small as possible was key to the design.
The system's designers tell me that it worked right the first time, with just a little tweaking required on both the hardware and the software. This was likely because each subsystem was tested individually along the way. That increases the probability of things working correctly when they're all assembled together.
The design time for the TL225 was roughly five months from concept to completion. That's typical for a project like this one. While some of the pieces were new to this design, some IP was borrowed from previous designs, thereby fast-tracking the project somewhat.
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