Continued from [3G iPod shuffle Teardown] SoC, Flash Memory Stacked [Part 4].
The connector in the upper part of the main board is used to connect with the flexible substrate mounted with the headphone jack, the slide switch, etc. The second-generation iPod shuffle, too, uses a headphone jack to transmit both serial signals for the USB interface and audio signals.
"It seems like the headphone terminal was divided into four areas and is used for (1) power supply for USB, (2) grounding, (3) plus signals for USB and either one of the stereo audio signals, and (4) minus signals for USB and the other of the stereo audio signals," the engineer said. "I think the IC, which is located near the connector, is an analog switch IC to switch between USB signals and audio signals.
The area of the third-generation main board is about 25% of that of the second-generation main board, which is 38.4 x 24.4 mm in size.
The area was reduced mainly by removing operation buttons such as the play/pause button and the volume control button on the main body. The main board of the second-generation iPod shuffle, which is equipped with a circular button, has five switches that receive inputs. This is the main reason for the size difference. In the second-generation product, an Li-polymer secondary battery is attached to the back of the portion with the switches.
Even compared with the main board of the second-generation product excluding the part with the five switches, the area of the new main board is about 30% smaller. This is partly because the SoC and flash memory of the new main board are placed in one location. When seen from the side, the semiconductor package looks like composed of two layers. Probably, the SoC and flash memory are stacked.
Battery capacity reduced to 2/3
The Li-polymer secondary battery of the third-generation iPod shuffle measures 16.4 x 12.8 x 3.5mm. Compared with the battery of the second-generation product, which measures 16.8 x 21.8 x 3.0mm, the battery capacity of the new product is about 2/3. So, the weight of the main body, which was reduced from 15.7 to 10.6g, was achieved by reducing the capacity of the secondary battery and the size of the chassis.