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HEATEVM: TI HEAT EVM Rev-B

David Shaddock96
Prodigy 110 points

Part Number: HEATEVM

I have a HEAT board that I am trying to communicate with using a J-Link Pro. The J-Link indicates the Reset pin is low and this prevents me from connecting to the MCU (U19, SM470R1B1M). I confirmed this by checking voltage on U19-69 RSTn, JP20-15, R81, and U18-3. All have nearly zero voltage. Unsoldering pin U19-69 makes JP20-15, R81, and U18-3 3.23V. It appears that U19 is pulling pin 69 low. Is there a way to reset this pin so it doesn't pull RSTn low or erase the program that might be driving this pin?

  • 0
    TI__Guru 62930 points
    David,
    First off, I need to note that this EVM is obsolete, and has very limited support.
    I believe the processor may be damaged, as the schematic only has a pullup R81, and connection to U18 RSTn line.
    The processor should not be driving this node low, unless it is executing a reset itself.

    I am not certain how the processor reacts at power up if clocking is not available. Possibly the clocking is not working and it is keeping reset asserted?

    Note that there was an error with the design, and the clock input to U19 pin 19 should be 1.8v signalling. The EVM drives 3.3V. This has worked reasonably well, but may provide for shorter lifetime of the clock input.

    If this answers your question, please click "Verify it as the answer"
    Regards,
    Wade
  • 0 in reply to Wade Vonbergen
    Prodigy 110 points

    Wade,

    I made a rework to the board using a voltage divider (1kohm series, 1.5kohm to GND) to drop the OSCIN voltage to about 1.8V. I powered up the board but still get a RST pulled low. The wave form isn't a nice square wave and has a charge up on the leading edge. Do you think this would be accepted or is there an internal circuit to square it up? I have another SM470R1B1M-HT that I am swapping with the one on the board to see if that makes the heat board work.

    Dave

  • 0 in reply to David Shaddock96
    TI__Guru 62930 points
    I am not certain how well it will work long rise and duty cycle distorted.
    This device has a zero pin PLL. You might try pulling PLLDIS high, to see if that improves operation.

    Since RST is stuck low, there may be other issues with the device on the board.

    Regards,
    Wade
  • 0 in reply to Wade Vonbergen
    Prodigy 110 points

    I replaced the SM470R1B1M-HT (U19) along with the voltage divider resistors and I am able to connect to it using J-TAG. The backside contact was difficult to make using hand soldering but it seems to be working now.

    I think I am good to go. Thanks for your help.