Withings GO Teardown

ID: 66776

Description: Please find the full blown teardown on our blog...

Steps:

  1. From left to right: silicone wristband, clip, tracker and plastic coin to open the casing
    2. Step image
  2. You can simply open the back of the casing with the included tool or with a regular coin to remove the battery
  3. The battery that is used is a Panasonic 3V CR2032 with a capacity of 225mAh
  4. Removing the battery also exposed a seal ring used to make the enclosure waterproof.
  5. FCC ID: XNAWAM02
    6. Step image Step image Step image
  6. The casing itself consists of three parts: the top, the bottom and a thin cover for the e-ink display.
  7. Separating the parts seemed tricky at first, because they were sealed together, but by chipping some plastic off the side with my utility knife I managed to create a small opening. After that, I could easily cut open the casing around the seam.
    8. Step image Step image
  8. The PCB was manufactured by a Chinese company called PLOTECH
  9. The back of the PCB immediately shows a bunch of testing points which are labelled on the silkscreen layer with TPXX.
  10. The connectors Withings used are called "Front Flip FFC/FPC Connectors" and are very easy to open with a pair of tweezers. (FFC stands for Flat Flexible Cable).
  11. Between the e-ink display and the PCB there is a support frame installed, this to keep the display in place and to avoid contact between the display and the PCB components.
    12. Step image Step image Step image
  12. On the top side of the PCB, in the middle, there is an SMD push button. The display is so thin and flexible you can actually press the button with it.
  13. The button is used to set-up the tracker when you unbox it and to switch from "tracker"-view to "watch"-view while using it.
    14. Step image
  14. The ultra low-power 3-axis accelerometer on the board is the ADXL362 from Analog Devices (datasheet).
  15. Next to the accelerometer there is another chip, a push button reboot controller XC6190 (datasheet).
    16. Step image Step image
  16. The bluetooth chip Withings has chosen is the nRF51822 from Nordic Semiconductors. It's a 2.4GHz ultra low-power bluetooth chip built around a 32-bit ARM® Cortex™ M0 CPU.
  17. The big white SMD component you see on the right side of the PCB is an RF ceramic chip antenna from Johanson Technology (datasheet).
  18. Below the bluetooth chip there are two crystal oscillators. According to the datasheet of the nRF51822 the system uses 2 clocks: A high frequency clock (HFCLK) and a low frequency clock (LFCLK). The HFCLK is fixed to 16 MHz and the LFCLK is fixed to 32.768 kHz.
  19. The balun, BAL-NRF02D3 (datasheet) from STMicroelectronics, next to the bluetooth radio is used to match the impedances. This balun is actually optimized for the nRF51822. Read this blog post to understand why a balun is used in this circuit: https://devzone.nordicsemi.com/blogs/655...
    20. Step image Step image Step image
  20. The big black "blob" (glob-top) on the top of the PCB, is what I assume the display driver. The blob is actually a protective cover for the chip and the wire-bonds. This type of method is called "chip-on-board" (COB). Black epoxy resin is used as the chips can be sensitive to light, it's the same material used for the packaging of ICs.
  21. You can find a very nice article on Sparkfun on how these types of chips are made: https://learn.sparkfun.com/tutorials/how...
    22. Step image
  22. The display is only 0.45mm thick, that's very thin! The display does contain a serial number "SCD72E00-160418-1". The company eink is the manufacturer.
  23. The cool thing about e-ink displays though is that they keep displaying their last state even if they are not connected to a battery. The ultimate proof that these displays are ultra low-power.
    24. Step image Step image
Back