BOS1921 ·

My BOS1921 board design is not working, there is no waveform output

Question:

I created by own board, but the BOS1921 does not output any waveform on my piezoelectric actuator. What do I do wrong?

 

 

Answer:

 

There can be many reasons why the waveform does not play or output correctly. A step-by-step approach will help single out hypothesis and find the cause. Here are some guidelines to follow when debugging waveform output.

 

Test Equipment:

  • Use an oscilloscope to monitor the output voltage and key voltage nodes such as VBUS, VDD, VOUT(+/-). It can give tremendous insights on what causes the issue.

  • Use a Logic Analyzer to monitor and verify digital communication.

 

Typical Verification Flow:

  1. If the custom board can be driven from an external supply and I2C controller, try connecting it to the BOS1921-KIT controller board and connect it to Haptic Studio. Since this platform is already developed and have passed through quality control, this is a quick and efficient way to check if the electrical performance is appropriate.

  2. Check the driver output voltage on an oscilloscope.

    1. Look at VOUT+, VOUT-, but monitor VBUS/VDD as well.

    2. Is the output waveform playing at all?

    3. Is the voltage on OUT+/OUT- close to VDD before/after the waveform?

    4. Does the output waveform shape seems random, or is it systematically failing the same way?

    5. At the moment of failure, what is happening on VBUS/VDD?

  3. Check the I2C communication.

    1. Are SCL/SDA correctly pulled up to VDDIO?

    2. Is the CHIP_ID read correctly after power up?

    3. Check the protocol.

    4. Is the IC acknowledging?

  4. Check power up sequence.

    1. Is VBUS rising fast enough (see specification)?

    2. Is VREG pin rising then falling (entering SLEEP) after VBUS rise?

    3. Is VDDIO rising after VBUS?

  5. Check the coding sequence. Use the provided SDK for ease of integration and reliable operation.

  6. Check that BOM fits requirements given by the datasheet or BOM generator.

  7. Check that layout guidelines have been followed.

     

Supply Rise:

The CHIP_ID should be checked and returned correctly at initialization. If its value is wrong, it may be an indication the VBUS supply rose too slowly. Checking VREG behavior helps confirm this hypothesis. Check the product datasheet for details and the application note on Power Up for guidelines to managing this potential situation.

 

Supply Sequence:

If the BOS1921 does not acknowledge on an I2C transaction, it may be caused by a wrong supply sequence of VBUS and VDDIO. Check the product datasheet for details and the application note on Power Up for guidelines to managing this potential situation.

 

Software (Register) Commands:

Check the software register commands sent. A logic analyzer is useful to confirm commands sent to and read from the Boreas driver. Use the SDK to ease integration. Product features are already programmed, debugged and examples for most useful operations are provided. Once your BSP is defined and working, there is very little programming work needed.

 

BOM:

The selected BOM might not be suitable for the application conditions (piezo capacitance, amplitude, frequency). Use the online BOM generator for guidance on components requirements. Also consult our application note on BOM Selection to understand each component and their key requirements (it was written for the BOS1901 but it is applicable to all products).

Swap the BOS1921-KIT driver board BOM for the selected application BOM and test it using the development kit and Haptic Studio. Check that the BOM is suitable for the given load and application conditions; use the piezo evaluation tool in Haptic Studio to confirm the operation space. You can also use Haptic Studio to optimize parameters for this BOM prior to building the custom board.

 

PCB Layout:

Board layout is critical to get good behavior and performance using Boréas drivers. Follow the guidelines given in the datasheet. Consult the application notes on PCB layout available on our website; it provides key information on critical aspects of the layout.

 

If all else fails:

If after checking all the above, you still have issues, please contact Boreas technical support. Please provide a detailed description of your issue, and scope and logic analyzer captures showing the issue.

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