CC2650 SensorTag DevPack Breakout Board

Design files for the SensorTag DevPack Breakout Board can be obtained from Circuit Maker. Circuit Maker is a free PCB design tool from Altium. Designs can be imported into Altium Designer.

CC2650 Sensor Tag DevPack Notes

At the time of writing [October 2015], there is limited instructions from Texas Instruments on how to build your own DevPack for the CC2650 SensorTag. These notes have been derived from studying the Build Your Own DevPack "Guide" and the SensorTag / example DevPack schematics.

Connector

The CC2650 Sensor Tag includes a 20 pin Samtec connector, Part No LSS-110-01-F-DV-A for spinning your own DevPacks. The connector is self mating, hence you don't need to worry about male and female versions.

Very few of the electronics catalog companies (RS-Components, Digikey, Mouser) stock this part. I acquired my connectors directly from Samtec, prior to Element-14 stocking the part (#2504990)

Pin Out

The following table details the SensorTag DevPack Expansion connector:

• Some pins are used for programming/debugging/on-board peripherals and are not generally available in development (Red).

• The SensorTag contains an analog switch used to switch power between the on-board battery and the external DevPack connector (pin 9). This switch can be operated by PWR_GOOD (pin 19).

• DP_ID (pin 17) appears to be set up as a voltage divider and used to detect the type of DevPack board connected. The SensorTag board has a 200k pull-up resistor to 3.3V. With no board connected, DP_ID should be approximately 3.3V. DEVPACK-DEBUG contains a 750k resistor pulling DP_ID low. DEVPACK-WATCH has a 820k resistor pulling DP-ID low and DEVPACK_LED_AUDIO has a 300k resistor.

SensorTag PCB Rev A 1.2.0 & Rev B 1.3.1

As per the above notes, SensorTag includes an analog switch to allow it to be powered from the on-board CR2032 battery, or external power.

Rev 1.2.0 of the PCB (Rev A) included a TS5A3159A 1 Ohm SPDT Analog Switch, but could never correctly power the board in the absence of the on-board battery. Without the CR2032 inserted and with R23 not fitted, the analog switch as never powered. I would coach the board to start, by touching the BAT+ pad on the corner of the SensorTag board. This would provide enough energy to power the analog switch.

Rev 1.3.1 (Rev B) includes a major design change to the analog switch, replacing the existing part with the TPS22910A 5.5V, 2A, 61mΩ Active-Low Load Switch With Reverse Current Protection.

In this revised design, the DevPack Connector's pin 9 (VDD_OUT) is always directly connected to the Sensor Tag's VDD Supply. The load switch enables the battery, via the active low PWR_GOOD line. The load switch incorporates reverse current protection, ensuring the external power supply never attempts to charge the battery.

DevPack Schematics

Texas Instruments appear to have multiple product pages for the Sensor Tag DevPacks, some with schematics and some without. This makes finding the schematics and design files for DEVPACK-DEBUG, DEVPACK-WATCH and DEVPACK_LED_AUDIO files difficult if you land on the wrong page.

Below is a list of direct links:

• Debugger DevPack Schematic - Linked from Debug DevPack Folder
• LED Audio DevPack Schematic - Linked from LED Audio Folder
• Watch DevPack Schematic - Linked from Watch DevPack Folder
• Wireless pH Sensor Schematic - Linked from Wireless pH Sensor Folder