Microchip dsPIC33C Digital Power Starter Kit - Review

Table of contents

RoadTest: Microchip dsPIC33C Digital Power Starter Kit

Author: gordonmx

Creation date:

Evaluation Type: Development Boards & Tools

Did you receive all parts the manufacturer stated would be included in the package?: True

What other parts do you consider comparable to this product?: Other Dev Kits

What were the biggest problems encountered?: Lack of clear documentation

Detailed Review:

First off, I would like to thank Microchip and Element 14 for the opportunity to evaluate the Microchip dsPIC33C Digital Power Starter Kit (DPSK), P/N DM330017-3(“the board”). 

 

Summary Conclusion –

For me this was a very fun demo board evaluation for a couple of reasons. First, I hadn’t worked with a Microchip board in a while so it gave me a chance to refresh myself with their work. Second, I hadn’t work on a power supply design for an even longer period of time.  Third, it uses a digital signal controller (DSC) at its core (ooh, this will always sound like fun).  Fourth, the code is available to review (and try out some things).  Fifth, the board has everything needed, even down to actual load resistors, to demonstrate the working of the dsPIC33.  I could go on, but back to the summary. 

 

As mention in the body of my review, the board isn’t an actual dev kit, but a reference design/demo board.  Over 40 different test points are defined so that waveforms can easily be accessed and evaluated.  This makes the board a great tool for those wishing to learn the basic of a switch mode power supply (SMPS) design using Microchip’s DSC devices.  Microchip also has a couple of useful app notes (AN1114 & AN1207) that is a deeper dive in to the topologies of SMPS.

 

But then I broke the board, or at least the 3.3V output.  But still I like the kit, if not for any other reason than the educational aspect.

 

Pros –

  • Complete reference design based of Microchip’s dcPIC33CK256MP505 single core DSC including:
  • Both Buck and Boost converter stages,
  • On-board passive loads,
  • PICkit™ On-Board (PKOB) Programmer/Debugger Circuit
  • USB/UART Hub and Bridge
  • Temperature Sensor
  • 2x16 Character LCD
  • Over 40 designated test points
  • Free to use standard proprietary IDE and other design software,
  • Open community user forum,
  • Second (& maybe third) generation design.

 

Cons –

  • The documentation was limited in the area of pre-installed demo program.  From how to user the demo program to the source code supplied, the documentation gives very little details.
  • As mentioned in the summary, after hours of experiencing with the board the buck output (3.3Vdc) stopped operating with an over-current flag.  I would have been nice to have a troubleshooting guide.

 

Wish List –

  • Add clearer instructions for compiling and installing the demo code.
  • Add more details on the operation of the demo program, especially the test program.

 

Useful Document Links-

NOTE:  Logging in to the respective websites may be required to access some of the documents.

 

 

Microchip Software Tools –

 

NOTE:  Like much of the software provided, the standard versions of the XC C compilers are available as free, unrestricted-use downloads.  The standard version is enough for exploring the features of simpler designs, but for larger project the commercial “pro”, not so free, version is available with additional optimization levels.

 

Additional Resources -

 

NOTE:  The following are links to another interesting tool for an additional dev power board (DM330029/MA330048) made by Microchip for the dsPIC33CK256MP506 DSC, but not cover in this review:

 

Part I – What is the Microchip dsPIC33C Digital Power Starter Kit (DPSK)

Before diving into my actual review of the Microchip dsPIC33C Digital Power Starter Kit (DPSK), P/N DM330017-3, let’s take a look at what it is. The User’s Guide overview states the purpose of the board “is intended to introduce and demonstrate the capabilities and features of the Microchip SMPS families of devices.

 

In my view the board itself falls more in the category of a reference design.  Since the pre-installed demo code is available to play with it is more than just a demo board.  Along with the main dsPIC33 DSC chip comes all the supporting circuitry and components (mostly from Microchip), such as MOSFETs and drivers ICs, etc.  With the detailed components, schematics and code examples the circuit could easily be adapted to other product designs. 

 

As an interesting side note the DM330017-3 it the 3rd generation of the starter kit, hence the “-3”.  In my search for more information on the kit, I was able to find the “-2” documentation and found that a lot of the current user’s guide to be “cut & pasted” from it.

 

The following is the block diagram of the board from the User’s Guide.

 

 

In the above diagram, the DSC is located in the control block.  The buck and boost converter blocks include Microchip analog FET drivers, MCP14700 and MCP14A0152, respectively along with the appropriate power MOSFETs.  The protection and on-board load control block includes the supervisory circuitry that offers feedback to the controller block. A general purpose, 16-bit flash Microchip PIC24FJ64GA004 MCU is the heart of the supervisory circuit, as well as load, USB and PICKit on-board control.  So as you can see this reference design is Microchip.

 

A more detailed system diagram of the board is shown below:

A few features that truly help in the evaluation of the board are the built-in loads, the many labeled test points and status LCD.

 

Part II – The Unpacking: 

I have read many different views on the value and/or importance of the unpacking segment, but I feel it is important because it is often our first glimpse into what to expect in the product and support.  I was especially interested in their touchscreen technology.

 

The shipping box arrived undamaged, always a good sign, and well packed. Obviously, it wasn’t shipped by Amazon 8^).  The box within a box included everything need to power on the board; USB cable, external 9V power supply and of course the “board” itself, but no documentation (i.e. quick start guide, etc.).  However a quick google search did lead me to Microchip’s link to a user’s guide.

 

The “Kit’s” packaging –

   

The “Kit’s” Content, Front and Back –

   

The locations of the

    Broad Label & Test Point Example                          Buck/Boost Load Resistors & Push Buttons Ctrl      Status LCD, dsPIC33 IC (U40) & Power Circuit

 

 

Part III – Initial Board Power On:

 

At this time I normally power up the kit to get a feel for whether the unit will show any sign of life.  The good news is it did power up (i.e. no smoke or blank-screen-of-death). 

 

 

 

The pre-install firmware initial boot LCD display is shown below.  Each screen will advance automatically every 2 seconds.

à à   à   à   àBack to the original screen

   

By pressing the [USER] button (S2) shown in the previous section the LCD displays the status of the buck and boost supplies.  At the end of the status screens the display will return to the start-up screen.

 

 

 

The first screen is the average output voltage of each supply as taken using the DSC internal ADCs. 

The next screen shows the power output of the Buck converter.  Each screen represents a different load on the Buck supply; 0%, 10% (100 mA), 50% (500 mA) and 100% (1000 mA), respectively.  Each load level is manually advanced by pressing switch S10.

The load LEDs (LD10, LD11 and LD12), located on the upper right side of the board next to the output terminals, indicate which resistor packs are active. 

NOTE:  The power up default load configuration is no load as indicated by the load LEDs (LD10 thru LD15).  However many switching power supplies may exhibit some stability issues under no load condition.  And such is the case with the 3.3V supply which had ~250mv oscillation at ~10 KHz on top of the 3.3VDC output.  Sorry no pictures are available because I blew-up the 3.3V supply before I could take one.

 

NOTE:  For both the Buck and Boost converters, the power displayed is calculated using the output voltage and the load resistance since the on-board circuit for measuring the actual output current is not loaded.  The best the current design (punt intended) can do is check for excessive output currents and act accordantly.

 

In addition to manually stepping through the load levels, the loads may be stepped from either 10% to 50%, 50% to 100% or 10% to 100% by holding down the switch S10 for 2 seconds.  Switch S10 is used to select which step to run and is indicated by the load LEDS.  The duration of each step is 100ms with a 50% duty cycle. 

 

NOTE:  Once the step mode has been initiated the only way to exit the mode is by power cycling the board.

 

 

The next screen shows the power output of the Boost converter.  Each screen represents a different load on the Buck supply; 0%, 15% (30 mA), 50% (70 mA) and 100% (200 mA), respectively.  Each load level is manually advanced by pressing switch S11.

In addition to manually stepping through the load levels, the loads may be stepped from either 15% to 50%, 50% to 100% or 15% to 100% by holding down the switch 11 for 2 seconds.  Switch S11 is used to select which step to run and is indicated by the load LEDS.  The duration of each step is 100ms with a 50% duty cycle. 

 

NOTE:  Once the step mode has been initiated the only way to exit the mode is by power cycling the board.

 

The next screen shows the input voltage to the board and the temperature of the thermal sensor located between the Buck and Boost converter load resistors.  When the load temperature reaches 65 C the overheat (OH) LED (LD18) turns.  Above 75 C the OH LED will continually blink.  The LED will automatically turn off once the temperature drop to below 55 C.

The final 3 screens cover the fault indicators for both converters and general faults.  The Buck and Boost screen covers over current (OC) and voltage (OV) status, respectively.  If either condition exists the value changes from 0 to 1.  For the general fault indicator the documentation is silence.

Part IV – OOPS!

Beyond the initial board power-on I tried a number of simple tests.  The static load tests were part of the initial power on section above.  Since SMPS designs are not new to Microchip and this being the 3rd generation of the starter kit I had assume the design would be very robust.  So must for assumptions.  My plan was to try a few load stepping tests, along with power input limits and temperature and current limit testing.

 

Since these tests were just preliminary, and my final tests were going to be more detail, I unfortunately did not take many screenshots.  I did take some notes. 

 

Jumping to my OOPS moment, I was using an external DC supply set to the upper limit (13.5V) to power the board.  The Buck and Boost converter loads were set to max 1 and .2 amps, respectively.  I was monitoring the output voltages from their startup waveform triggered by the board reset switch (S1).  Both outputs had some dropouts during startup that I was interested in.  I had just finished pressing the reset switch for the 5th time separated each by ~5 seconds when the Buck Error LED (LD16) came on and its output rose to only .2V.  The Buck Faults LCD screen indicated an over current (OC) event, but no fault bits were triggered, as shown below

          

Buck faults:
OC 1 OV 0 REG 0

        

Fault bits:

0 0 0 0 0 0 0 0

           

Other interesting findings were:

·  As mentioned in the initial board power-on section, the Buck converter had a ~250mv oscillation at ~10 KHz under a no load condition, but this could be normal for the design.  The Boost supply did not have the oscillation.

·  Aside from the no load oscillation, both supplies had ~50 mv switching noise on their respective outputs.

·  Although the input voltage and output current limitations seems to relate to hardware limits, the actual shutdown protection is controlled by the firmware or supporting components.  When I tried to drop the input voltage to less than 6 Vdc or greater than 14 Vdc the firmware flips a fault bit.  However, I believe only the 3.3 V converter shutdowns with the fault.  As a side note, this is not necessarily a bad thing.

        

Fault bits:     

1 0 1 0 0 0 0 0

Input Voltage - Under            

Fault bits:     
1 1 0 0 0 0 0 0

Input Voltage - Over

           

·  I saw no noticeable steps in the output of either supply during load stepping.

·  When the board is reset (S1) the 15V Boost output does not go to 0V, but drops from 15 to ~12.5Vdc for ~750ms, load depend.  The Buck output dropped to ~0V.

 

·  When the board is power-on (13.5V ext supply) the boost output jumps to 13.3 Vdc for the first 1 second before stepping up to 15 V (no load condition).

 

Part V – Microchip MPLAB X IDE Software:

 

Before jumping into the installation process, I wanted to show you my PC information:

 

Although I did install the MPLAB X IDE I did not attempt to build the demo code since the board was not fully functional.  This was a fresh install and I didn’t have any major issues, but I must say that the installation instructions were at times confusing. 

 

The required IDE for the starter kit, as specified in the documentation is:

 

  • MPLAB XC16 supports all 16-bit PIC MCUs      and dsPIC® Digital Signal Controllers (DSCs)

 

The standard version of the IDE is free and unrestricted, but not completely “unrestricted”.  I know that doesn’t make complete sense, but that is in reality what the website implies because they want to sell you the “pro” version.  The standard version is enough for exploring the features of simpler designs, but for larger project the commercial “pro”, not so free, version is available with additional optimization levels.

 

My only issue with the IDE is that the installation is a 2 step process.  After installing the IDE you must also download the C compiler installation.  Most current vendors I have used include the compiler installation in the IDE install download automatically.

 

 

The final MPLAB v5.50 IDE flash screen is shown below:

When the board is plugged into the USB port the drivers were automatically loaded.  NOTE: even though the pop-up window said the driver software was NOT successfully installed, they were.

The resulting device manager screen is shown below:

Part VI – Conclusion

As mentioned earlier the goal in my review is to evaluate the out-of-the-box experience with Microchip dsPIC33C Digital Power Starter Kit (DPSK), P/N DM330017-3.  Was the documentation complete?  Were the items included or readily available enough to evaluate the advertised features?  Were code examples available?  Was support available?  Was support helpful?  My answer too many of these question would be marginable at best.  But I like the kit, if not for any other reason than the educational aspect.  I really recommend reviewing the tutorial documentation and Microchip university videos mentioned in the Useful Documents section of this review.

 

I hadn’t worked with Microchip or SMPS supplies and there are a lot of details to digest in coming up to speed with the kit, but it was very enjoyable. 

 

What I didn’t try

Although I installed the IDE to try to compile the demo code, I never got around to completing this step due to the failure of the 3.3V converter.

 

What’s next?

I would like to continue to troubleshoot the failure of the 3.3V output, then try compiling the demo code and upload the binary to the board. 

 

Please let me know if I missed something in the documentation.  Also please pardon my typos.

 

Gordon Margulieux

 

Twin Falls, ID USA

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