Teardown Pebble Smartwatch

2016-06-20 | By All About Circuits

License: General Public License

Courtesy of All About Circuits

Introduction

Pebble is a manufacturer of smartwatches with E-Ink display that offer a long battery life. In this teardown we are going to take a look at the insides of the original Pebble smartwatch, now referred to as the Pebble Classic.

Primary Circuit Board

There are two circuit boards inside of this smart watch. The primary circuit board is a typical multilayer fiberglass circuit board that has nearly all of the active electronics on it.

The Primary PCB in the Pebble Smartwatch

On the rear of the primary circuit board are many test points, the antenna connector, and a Bluetooth IC.

The Back of the Primary PCB

Secondary Flex Circuit Board

Attached to the primary circuit board is a secondary flexible circuit board manufactured by CMI. This secondary circuit board contains the LEDs for the display’s backlight, the bluetooth antenna, and dome switches for user input.

The Flexible Circuit Board in the Pebble

The flexible circuit board is mated to the primary board through a low profile surface mount connector.

The Connector from the Flexible PCB to the Main PCB

Screen

One of the primary features of the Pebble Smartwatch is the epaper display. The display is a 1.26” display manufactured by Sharp, part number LS013B7DH05. This a 144x168 pixel display that has a very low power consumption when there is a static image on the screen. This ultra low power consumption of the display is one of the reasons why the Pebble line of smartwatches can last so long on a single charge.

The E-Paper Screen in the Pebble Smartwatch

The screen connects to the circuit board through an elastomeric connector, often called a zebra connector. These connectors use insulating and conductive rubber compounds to transfer power and data. Surrounding the insulator and conductor core are flanks made of light blue rubber of a softer durometer.

The Elastomeric Connector on the Display

On the circuit board, there are 9 gold plated pads that the zebra connector sits on. These connect to the 10 terminals on the display. The thicker gold fingers are used for power. The other six connectors are used for the serial data inputs.

The Gold Contacts for the Zebra Connector

Due to the technology used in the display, it is not self-illuminating, as opposed to AMOLED displays. To make the smartwatch usable in low light conditions, 3 surface mount LEDs are used to act as a backlight.

The LEDs for the Screen Backlight

Battery

Powering the smartwatch is a single cell 130mAh lithium battery. This battery is manufactured by Fullriver, part number 402222. Physically the battery is 3.9mm by 21.5mm by 21.0mm and weights 4.0g. The battery can be charged at a rate of up 65mA and has a maximum discharge rate of 130mA.

The 130mAh Fullriver Battery

Paired to the battery is a small circuit board that provides protection to the battery cell.  The electronics on this small circuit board prevent damage caused by over discharge and short circuits.

The Protection PCB on the Battery

To charge the battery the Pebble uses a Texas Instruments BQ24040 charging IC. The charging IC has an adjustable input current of 100mA or 500mA. The reference design for this charger only uses 5 passive components, 3 resistors and 2 capacitors.

The Texas Instruments Charge IC labeled NXE

Bluetooth

When the Pebble was first launched on kickstarter it used a different bluetooth module, a Panasonic pan1316 Bluetooth module. This is a new revision of the pebble and it uses a Texas Instruments CC2564 Bluetooth IC.

The CC2564 Bluetooth Low Energy IC 

To connect the bluetooth IC to the antenna on the flexible circuit board a gold plated spring contact is used.

The Bluetooth Spring Contact

The spring contact mates to a gold plated contact pad the flexible circuit board. The contact pad is attached to a small trace antenna on the flexible circuit board.

The Bluetooth Trace Antenna

Microprocessor

To control the functionality of the Pebble there is a Cortex-M3 microprocessor packed inside of it.  The Pebble uses a STMicroelectronics STM32F205RE, that can be seen in the image below in the CSPBGA package.

The STMicroelectronics Cortex-M3 Microprocessor

The Pebble has 32Mb of internal flash memory. The Pebble uses a N25Q032A11ESE40F flash memory IC manufactured by Micron. This flash memory IC communicates with the STM32 microprocessor via an SPI bus.

Sensors

To track steps, detect wrist movements, and to track sleep the Pebble smartwatch uses two sensors. The first is a digital magnetometer, this is a 3 axis digital compass. This magnetometer is made by Xtrinsic and is part number MAG3110.

The Magnetometer is Labeled MAG KWV

The second sensor that the Pebble Smartwatch uses is a 3 axis accelerometer made by STMicroelectronics. This sensor is part number LIS3DH and is in a 16 pin LGA package.

The Accelerometer is located in the Center of the Image

Conclusion

Pebble has made a few change since the initial design of the Pebble Smartwatch. The newer versions of the Pebble smartwatch have 4 Torx screws holding the watch together rather than globs of glue. The newer versions of the Pebble Smartwatch also feature a Ti Bluetooth IC as opposed to a Panasonic pan1316 Bluetooth Module. Compared to other smartwatches, such as Android Wear devices and Apple Watches, Pebble’s line of watches are more basic without features such as GPS, touchscreens, and LCD displays. The simplicity of the Pebbles help them have some of the longest battery life in the smartwatch market.

Scheme-it:  http://www.digikey.com/schemeit/project/pebble-smartwatch-NDTGLC820330/

製造商零件編號 BQ24040DSQR

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製造商零件編號 CC2564YFVR

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